dr.n.g.p.institute of technology coimbatore 48

Dr.N.G.P.Institute of Technology

Coimbatore – 48

DEPARTMENT OF

ELECTRONICS AND COMMUNICATION ENGINEERING

LABORATORY MANUAL

EC 6411 – CIRCUITS AND SIMULATION

INTEGRATED LABORATORY

IV SEMESTER ECE

R2013

Prepared by

C.SENTHILLUMAR, ASP /ECE

WWW.Vidyarthiplus.Com

SYLLABUS

EC6411 CIRCUITS AND SIMULATION INTEGRATED LABORATORY

L T P C 0 0 3 2

OBJECTIVES:

To gain hands on experience in designing electronic circuits.

To learn simulation software used in circuit design.

To learn the fundamental principles of amplifier circuits

To understand Bias in Amplifier circuits

To differentiate feedback amplifiers and oscillators.

To study the characteristic of source follower

To understand the concepts of multivibrators

DESIGN AND ANALYSIS OF THE FOLLOWING CIRCUITS

1. Series and Shunt feedback amplifiers-Frequency response, Input and output impedance

calculation

2. RC Phase shift oscillator and Wien Bridge Oscillator

3. Hartley Oscillator and Colpitts Oscillator

4. Single Tuned Amplifier

5. RC Integrator and Differentiator circuits

6. Astable and Monostable multivibrators

7. Clippers and Clampers

8. Free running Blocking Oscillators

SIMULATION USING SPICE (Using Transistor):

1. Tuned Collector Oscillator

2. Twin -T Oscillator / Wein Bridge Oscillator

3. Double and Stagger tuned Amplifiers

4. Bistable Multivibrator

5. Schmitt Trigger circuit with Predictable hysteresis

6. Monostable multivibrator with emitter timing and base timing

7. Voltage and Current Time base circuits

TOTAL: 45 PERIODS

OUTCOMES:

On completion of this lab course, the students will be able to

Analyze various types of feedback amplifiers

Design oscillators, tuned amplifiers, wave-shaping circuits and multivibrators

Design and simulate feedback amplifiers, oscillators, tuned amplifiers, wave-shaping

circuits and multivibrators using SPICE Tool.


CONTENTS

S.No Date Name of the Experiment Marks Lab

Inchagre 1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

Content Beyond the syllabus (Using Virtual lab)

1

2

Marks (Average)


Ex.No.1 SERIES AND SHUNT FEEDBACK AMPLIFIERS-FREQUENCY

RESPONSE, INPUT AND OUTPUT IMPEDANCE CALCULATION Date:

A. CURRENT SERIES FEEDBACK AMPLIFIER

OBJECTIVE

To design and construct a current series feedback amplifier,

obtain its frequency response

measure input and output impedances

EQUIPMENT

S.No. Description Range Qty

THEORY

The circuit diagram of CE Amplifier with current series feedback is shown below. The resistor RF in emitter is the feedback element. The voltage drop Vf across RF constitutes the feedback signal while the current Ic forms the sampled signal. Hence, this forms a current series feedback .Due to negative feedback, though the voltage gain of the amplifier is decreased, it improves stability and increases the bandwidth. This is the advantage of negative feedback. Using h-parameter model for ac analysis the amplifier parameters such as the voltage gain, bandwidth can be calculated. For this, following steps have to be followed.

To find the input circuit, set I0=0, ie open the output loop. Hence RE appears in input side.

To find the output circuit set I1=0, i.e. open the input loop. Hence RE appears in output loop.

DESIGN

VCC = 12V, IC = 1mA, AV = 40


Transistor BC107: hie = 1.1KΩ, hfe = 220

Typical values: VCE = 3V; VRE = 5V

Selection of RC & RE

Applying KVL on Collector loop, VCC = VRC + VCE + VRE

VRC = VCC – VCE – VRE =

RC = 𝑉𝑅𝐶 𝐼𝐶

=

RE = 𝑉𝑅𝐸𝐼𝐸

=

𝑉𝑅𝐸

𝐼𝐶 = (since IC = IE)

Selection of RL

RL = 10 RC =

Selection of R1 & R2

Typical value of R2 = 10 RE =

I2 = 𝐼𝑐10

=

VB = VBE + VRE = (VBE = 0.7V for Si Transistor)

R1 = 𝑉𝑐𝑐−𝑉 𝐵𝐼2

=

Selection of Rf

AV = −( RC || RL)

𝑅𝑓

Rf = −( RC || RL)

𝐴𝑉 =

Now RE = RE – Rf =

Selection of CE

XCE = Rf at f1 ; f1 = lower cutoff frequency = 100Hz

XCE = 12𝜋 𝑓1 𝐶𝐸

= Rf

CE = 12𝜋 𝑓1 Rf

=

Selection of C1 & C2

XC1 = 𝑍𝑖𝑛+𝑟𝑠10

at f1 ; f1 = lower cutoff frequency = 100Hz


Zin = R1 || R2 || (hie +(1+hfe) Rf) =

rs = 600Ω

𝑍𝑖𝑛+𝑟𝑠10

=

XC1 = 12𝜋 𝑓1 𝐶1

= 𝑍𝑖𝑛+𝑟𝑠10

=

Now, C1 = 1

2𝜋 𝑓1 𝑍𝑖𝑛+𝑟𝑠10

=

XC2= 𝑍𝑜10


Zo = RC + RL

XC2= 12𝜋 𝑓1 𝐶2

= 𝑍𝑜10

Now, C2 = 1

2𝜋 𝑓1 𝑍𝑜10

=

PROCEDURE

Frequency Response (with feedback)

1. Connect the circuit as shown in the figure.

2. Connect a sine-wave generator set at 1000Hz frequency and 50mV peak-to-peak signal voltage at the

input of the amplifier circuit.

3. Connect an oscilloscope across the output nodes. Observe the sine wave output on the oscilloscope.

Adjust the output of the sine-wave generator until undistorted. Maximum signal output is obtained.

4. Observe and measure the peak-to-peak amplitude of input and output signal and record the values in the

tabulation provided.

5. Now, sweep the input signal frequency in the range 30Hz to 1 MHz by adjusting the sine wave generator

output.

6. For each setting of input frequency, measure the output signal voltage.

7. Draw the frequency response curve on a semi-log graph sheet. From this plot, obtain the values of mid-

band voltage gain, upper and lower cut-off frequency and BW (fh-fl).

Frequency Response (without Negative Feedback)

8. Remove Rf from the circuit and connect RE and CE directly to the emitter terminal.

9. Measure and record in the table, the frequency response of this circuit without Rf by repeating steps 5

through 6.


10. Draw the response curve on the same graph as before. Obtain the values of mid-band voltage gain,

lower and upper cut-off frequency and BW. Comment on the differences between this response curve and

the previous curve.

Impedance Measurement

Measurement of input impedance Measurement of output impedance

11. In the above assembled circuit, keep the magnitude and frequency of the source same, ie., Vi at 1KHz

frequency.

12. Connect a potentiometer Rin (variable resistance) in series with the circuit input terminal and the signal

source.

13. Connect a two-channel CRO to simultaneously monitor the input and output signal voltage waveforms.

14. Adjust the POT until a new output signal VO, equal to one-half the original measured value of VO is

obtained. Now, remove Rin from the circuit and measure its resistance using DMM. The measured value in

ohms equals the input impedance, Zi.

15. To measure the output impedance ZO of the amplifier, connect a potentiometer Rout to the output

circuit.


obtained. Now, remove Rout from the circuit and measure its resistance using DMM. The measured value

in ohms equals the output impedance, Zo.

17. Tabulate the readings in table.

CIRCUIT DIAGRAM


PIN SPECIFICATION OF BC107

TABULATION


Input Voltage Vi =

Frequency f

(Hz)

Output Voltage Vo

(V) Gain Av =

𝑽𝒐

𝑽𝒊

Gain in dB

20 log Av


Frequency Response (without feedback)

Input Voltage Vi =

Frequency f

(Hz)

Output Voltage Vo

(V) Gain Av =

𝑽𝒐

𝑽𝒊

Gain in dB

20 log Av



Particulars Measured Value Calculated Value

Input Impedance, Zi

Output Impedance, Zo

MODEL GRAPH

FL – Lower cut-off frequency without feedback

FU – Upper cut-off frequency without feedback

FLf – Lower cut-off frequency with feedback

FUf – Upper cut-off frequency with feedback

Bandwidth (without feedback) = FU - FL

Bandwidth (with feedback) = FUf - FLf


RESULT

1. The current series feedback amplifier is designed, constructed and its frequency

Response is plotted.

2. The input and output impedance of the constructed amplifier is measured.

B. VOLTAGE SHUNT FEEDBACK AMPLIFIER

OBJECTIVE

To design and construct a voltage shunt feedback amplifier,

obtain its frequency response

measure input and output impedances

EQUIPMENT


THEORY In Voltage shunt feedback amplifier, the feedback signal voltage is given to the base of the transistor in

shunt through the feedback resistor Rf. This shunt connection tends to decrease the input resistance and the

voltage feedback tends to decrease the output resistance. In the circuit Rf appears directly across the input

base terminal and output collector terminal. The feedback path consists of Rf and Cf. Since the feedback

tends to reduce the input, negative feeback exists. This feedback amplifier is known as transresistance

amplifier as it amplifies the input current to required output voltage


DESIGN

VCC = 12V, IC = 1mA, AV = 40



Feedback ratio β = -0.025 x 10-3 A/V





=


=

𝑉𝑅𝐸


Selection of RL

RL = 10 RC =



I2 = 𝐼𝑐10

=



=

Selection of Rf & Cf

Rf = - - 1𝛽

Rf =

XCf = 𝑅𝑓

10 at f1 ; f1 = lower cutoff frequency = 100Hz

XCf = 12𝜋 𝑓1 𝐶𝑓

= 𝑅𝑓

10 =

Now, Cf = 1

2𝜋 𝑓1 𝑅𝑓

10

=

Selection of CE


XCE = re’ at f1 ; f1 = lower cutoff frequency = 100Hz

re’ = 26𝑚𝑉𝐼𝐸

= 26𝑚𝑉𝐼𝐶

=


= re’

CE = 12𝜋 𝑓1 re’

=


XC1 = 𝑍𝑖𝑛+𝑟𝑠10


Zin = R1 || R2 || Rf || hie =

rs = 600Ω

𝑍𝑖𝑛+𝑟𝑠10

=

XC1 = 12𝜋 𝑓1 𝐶1

= 𝑍𝑖𝑛+𝑟𝑠10

=

Now, C1 = 1

2𝜋 𝑓1 𝑍𝑖𝑛+𝑟𝑠10

=

XC2= 𝑍𝑜10


Zo = (RC || Rf) + RL =

XC2= 12𝜋 𝑓1 𝐶2

= 𝑍𝑜10

=

Now, C2 = 1

2𝜋 𝑓1 𝑍𝑜10

=

PROCEDURE



2. Connect a sine-wave generator set at 1000Hz frequency and 50mV peak-to-peak signal voltage at the

input of the amplifier circuit.


Adjust the output of the sine-wave generator until undistorted. Maximum signal output is obtained.


4. Observe and measure the peak-to-peak amplitude of input and output signal and record the values in the

tabulation provided.

5. Now, sweep the input signal frequency in the range 30Hz to 1 MHz by adjusting the sine wave generator

output.

6. For each setting of input frequency, measure the output signal voltage.

7. Draw the frequency response curve on a semi-log graph sheet. From this plot, obtain the values of mid-

band voltage gain, upper and lower cut-off frequency and BW (fh-fl).

Frequency Response (without Negative Feedback)

8. Remove Rf from the circuit and connect RE and CE directly to the emitter terminal.

9. Measure and record in the table, the frequency response of this circuit without Rf by repeating steps 5

through 6.

10. Draw the response curve on the same graph as before. Obtain the values of mid-band voltage gain,

lower and upper cut-off frequency and BW. Comment on the differences between this response curve and

the previous curve.


Measurement of input impedance Measurement of output impedance

11. In the above assembled circuit, keep the magnitude and frequency of the source same, ie., Vi at 1KHz

frequency.

12. Connect a potentiometer Rin (variable resistance) in series with the circuit input terminal and the signal

source.

13. Connect a two-channel CRO to simultaneously monitor the input and output signal voltage waveforms.


obtained. Now, remove Rin from the circuit and measure its resistance using DMM. The measured value in

ohms equals the input impedance, Zi.

15. To measure the output impedance ZO of the amplifier, connect a potentiometer Rout to the output

circuit.


obtained. Now, remove Rout from the circuit and measure its resistance using DMM. The measured value

in ohms equals the output impedance, Zo.


17. Tabulate the readings in table.

CIRCUIT DIAGRAM

PIN SPECIFICATION OF BC147/547

TABULATION


Input Voltage Vi =

Frequency f

(Hz)

Output Voltage Vo

(V) Gain Av =

𝑽𝒐

𝑽𝒊

Gain in dB

20 log Av


Frequency Response (without feedback)

Input Voltage Vi =

Frequency f

(Hz)

Output Voltage Vo

(V) Gain Av =

𝑽𝒐

𝑽𝒊

Gain in dB

20 log Av



Particulars Measured Value Calculated Value

Input Impedance, Zi

Output Impedance, Zo

MODEL GRAPH

FL – Lower cut-off frequency without feedback

FU – Upper cut-off frequency without feedback

FLf – Lower cut-off frequency with feedback

FUf – Upper cut-off frequency with feedback

Bandwidth (without feedback) = FU - FL

Bandwidth (with feedback) = FUf - FLf


RESULT

1. The voltage shunt feedback amplifier is designed, constructed and its frequency

Response is plotted.

2. The input and output impedance of the constructed amplifier is measured.

Viva - Questions

1. What is meant by feedback?

A portion of the output signal is taken from the output of the amplifier and is combined

with the normal input signal. This is known as feedback.

(OR)

Feedback is a part of output is sampled and fedback to the input of the amplifier.

2. Give the different types of feedbacks used in amplifier circuits.

1. Positive feedback

2. Negative feedback.

3. Define the positive feedback.

When input signal and part of the output signal are in phase, the feedback is calledPositive

feedback.

4. Define negative feedback.

When input signal and part of the output signal are in out of phase, the feedback is called

negative feedback.

5. What type of feedback is used in oscillator?

Positive.

6. Give the classification of amplifiers.

The amplifiers can be classified into four broad categories: voltage, current, Tranconductance

and Tranresistance amplifiers.

7. Define feedback factor or feedback ratio.

The ratio of the feedback voltage to output voltage is known as feedback factor or feedback

ratio.


8. What is the purpose of mixer network in feedback amplifier?

The mixer network is used to combine feedback signal and input at input of an amplifier.

9. What are the advantages of introducing negative feedback?

1. Input resistance is very high.

2. Output resistance is low.

3. The transfer gain Af of the amplifier with feedback can be stabilized against Variations of

the h-parameters or hybrid π parameters of the transistors or the Parameters of the others

active devices used in the amplifiers.

10. List the four basic feedback topologies.

1. Voltage amplifier with voltage series feedback.

2. Transconductance amplifier with current-series feedback.

3. Current amplifier with current-shunt feedback

4. Transresistance amplifier with voltage shunt feedback

11. Give the expression for gain of an amplifier with feedback.

Avf = AV/ 1+ AV β

Where, Avf – feedback voltage gain. AV – Voltage gain.

β - Feedback factor

12. What is the effect of lower cut-off frequency with negative feedback?

Lower cutoff frequency with feedback is less than lower cutoff frequency without feedback by

factor (1+Amid β)

13. What is the effect of upper cut-off frequency with negative feedback?

Upper cutoff frequency with feedback is greater than upper cutoff frequency without

feedback by factor (1+Amid β)

14. What is the effect of negative feedback on bandwidth?

Bandwidth of amplifier with feedback is greater than bandwidth of amplifier without

feedback.

15. Why gain bandwidth product remains constant with the introduction of negative

feedback?

Since bandwidth with negative feedback increases by factor (1+A β) and gain decreases by

same factor, the gain-bandwidth product of an amplifier does not altered, when negative

feedback is introduced.

16. What is the effect of negative feedback on feedback distortion?

The frequency distortion is reduced with the negative feedback.

17. What is the effect of negative feedback on noise? The noise is reduced with the negative feedback.

18. What is the effect of negative feedback on non linear distortion? The linear distortion is reduced with the negative feedback.

19. What are the types of distortions in an amplifier?

1. Frequency

2. Noise and non linear


20.What type of feedback is employed in emitter follower amplifier?

Voltage series feedback.

Ex.No.02

RC PHASE SHIFT OSCILLATOR & WEIN BRIDGE OSCILLATOR Date:

A. RC PHASE SHIFT OSCILLATOR

OBJECTIVE

To design, construct a RC Phase Shift Oscillator using BJT for a desired frequency of oscillation and to

observe its output waveform.

EQUIPMENT


THEORY The circuit illustrates BJT version of RC phase shift oscillator using CE configuration. The circuit consists

of an amplifier circuit, causes a phase shift of 180o and 3–stage positive feedback network (each RC

combination introducing shift of 60o) create phase shift 180o, which satisfies Barkhausen criterion. The


Oscillator circuit doesn’t have any external input with it. Additional RC (feedback) stages improve the

stability of the oscillator. With the proper selection of R & C values, the phase of the voltage at the resistor

will be advanced by 60o. The frequency of oscillation of a RC phase shift oscillator is given by,

)46(2

1

KRCfo

, Where

R

RcK .

DESIGN

VCC = 8.6 V; Q = (VCE , IC) = (3V, 1mA)


Frequency of oscillation fo = 3KHz

CIRCUIT DIAGRAM



For Feedback network, Let R = 1KΩ, k = 2.75

Typical Values: VRE = 3V





=


=

𝑉𝑅𝐸




I2 = 𝐼𝑐10

=



=

Selection of CE

XCE = re’ at f1 ; f1 = lower cutoff frequency = 100Hz

re’ = 26𝑚𝑉𝐼𝐸

= 26𝑚𝑉𝐼𝐶

=

12𝜋 𝑓1 𝐶𝐸

= re’

CE = 12𝜋 𝑓1 re’

=

Selection of C1


XC1 = 𝑍𝑖𝑛10


Zin = R1 || R2 || hie =

XC1 = 12𝜋 𝑓1 𝐶1

= 𝑍𝑖𝑛10

=

Now, C1 = 1

2𝜋 𝑓1 𝑍𝑖𝑛10

=

Feedback Network

Selection of R’ & C

R’ = R – hie =

fo = 12𝜋𝑅𝐶 𝛤(6+4𝑘)

C = 12𝜋 𝑓𝑜 𝐶 𝛤(6+4𝑘)

=

PROCEDURE



3. Observe and measure the peak-to-peak amplitude and frequency of the output signal and record the

values in the tabulation provided.

4. Sketch the Output waveform on a graph.

TABULATION

Particular Amplitude(peak to peak)

A

Time Period

T

Frequency

f = 1/T

Output

Waveform

MODEL GRAPH


RESULT

The BJT version of RC phase shift oscillator for the given frequency is designed, constructed and the output

signal is observed.

Theoretical fo =

Observed fo =

B. WEIN BRIDGE OSCILLATOR

OBJECTIVE

To design, construct a Wein bridge Oscillator using BJT for a desired frequency of oscillation and to

observe its output waveform

EQUIPMENT


THEORY

The Wien Bridge Oscillator is so called because the circuit is based on a frequency-selective form of the

Wheatstone bridge circuit. The Wien Bridge Oscillator is a two-stage RC coupled amplifier circuit that has

good stability at its resonant frequency, low distortion and is very easy to tune making it a popular circuit as


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an audio frequency oscillator but the phase shift of the output signal is considerably different from the

previous phase shift RC Oscillator.

The Wien Bridge Oscillator uses a feedback circuit consisting of a series RC circuit connected with a

parallel RC of the same component values producing a phase delay or phase advance circuit depending

upon the frequency. At the resonant frequency ƒr the phase shift is 0o.

The feedback network consists of a series RC circuit connected to a parallel RC forming basically aHigh

Pass Filter connected to a Low Pass Filter producing a very selective second-order frequency

dependant Band Pass Filter with a high Q factor at the selected frequency, ƒr.

At low frequencies the reactance of the series capacitor (C1) is very high so acts like an open circuit and

blocks any input signal at Vin. Therefore there is no output signal, Vout. At high frequencies, the reactance

of the parallel capacitor, (C2) is very low so this parallel connected capacitor acts like a short circuit on the

output so again there is no output signal. However, between these two extremes the output

voltage reaches a maximum value with the frequency at which this happens being called the Resonant

Frequency, (ƒr).

At this resonant frequency, the circuits reactance equals its resistance as Xc = R so the phase shift between

the input and output equals zero degrees.

Frequency of Wein bridge oscillator, fr = 1

2𝜋𝑅𝐶 where, R = R1 = R2; C = C1 = C2

CIRCUIT DIAGRAM



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DESIGN

VCC = 10V, IC = 2mA

Transistor BC547: hie = 1KΩ, hfe = 200


Frequency of oscillation fo = fr = 3KHz





=


=

𝑉𝑅𝐸




I2 = 𝐼𝑐10

=



=

Selection of CE

XCE = ℎ𝑖𝑒1+ℎ𝑓𝑒


ℎ𝑖𝑒1+ℎ𝑓𝑒

=



= ℎ𝑖𝑒1+ℎ𝑓𝑒

=

CE = 1

2𝜋 𝑓1 ℎ𝑖𝑒1+ℎ𝑓𝑒

=

Selection of C1, C2 & C3

XC1 = 𝑍𝑖𝑛110


Zin1 = R1 || R2 || (hie + (1+hfe)RE)

XC1 = 12𝜋 𝑓1 𝐶1

= 𝑍𝑖𝑛110

Now, C1 = 1


=

XC2= 𝑍𝑖𝑛210


Zin2 = (R3 || R4 || hie)+ RC

XC2= 12𝜋 𝑓1 𝐶2

= 𝑍𝑖𝑛210

Now, C2 = 1


=

XC3= 𝑍𝑜 10


Zo = RC

XC3= 12𝜋 𝑓1 𝐶3

= 𝑍𝑜10

Now, C3 = 1

2𝜋 𝑓1 𝑍𝑜 10

=

Feedback Network

fo = 12𝜋𝑅𝐶

Assume C = 0.1μF


Now, R = 12𝜋 𝑓𝑜 𝐶

=

1 + 𝑅𝑓

𝑅𝐸1 ≥ 3

𝑅𝑓

𝑅𝐸1 ≥ 2

Rf ≥ 2 RE1

Assuming RE1 = 50Ω, Rf ≥ 100Ω (Use DRB to adjust Rf )

PROCEDURE






TABULATION

Particular Amplitude(peak to peak)

A

Time Period

T

Frequency

f = 1/T

Output

Waveform

MODEL GRAPH


RESULT

The BJT version of Wein bridge oscillator for the given frequency is designed, constructed and the output

signal is observed.

Theoretical fo =

Observed fo =

Viva - Questions

1. What is an oscillator?

An oscillator is a circuit which basically acts as a generator, generating the output signal which

oscillates with constant amplitude and constant desired frequency.

2. What is the difference between open loop and closed loop gain of the circuit?

S.NO Open loop gain

Closed loop gain

The gain of the amplifier is ratio The ratio of the output to input,

of output to input when no considering the overall effect of the

1. feedback is used is called open feedback is called closed loop gain.

loop gain

3. State the Barkhausen criterion for an oscillator.

1. The total phase shift around a loop, as the signal proceeds from input through amplifier,

feedback network back to input again, completing a loop, is precisely 00 or 3600.

2. The magnitude of the product of the open loop gain of the amplifier

(A) and the feedback factor β is unity. i.e., A β = 1.


4. Explain the concept of positive feedback.

The feedback is a property which allows to feedback the part of the output, to the same circuit as

its input. Such a feedback is said to be positive whenever the part tf the output that is fed back to

the amplifier as its input, is in phase with the original input signal applied to the amplifier.

5. From where starting voltage for the oscillator is derived?

Every resistance has some free electrons. Under the influence of room temperature, these free

electrons move randomly in various directions. In such a movement of the free electrons

generate a voltage called noise voltage, across the resistance. Such noise voltage provides the

starting voltage for the oscillator.

6. Why in practice A β is kept greater than unity?

To amplify small noise voltage present, so that oscillations can start, A β is kept initially greater

than unity.

7. Give the overall classification of oscillators? a. Waveform type (sinusoidal, square, triangular,etc.,)

b. Circuit components (LC, RC,etc.,)

c. Range of frequency –A.F (audio), R.F (radio)

d. Type of feedback (RC phase shift, Wein bridge are feedback used, UJT relaxation

oscillators uses no feedback)

8. What is the gain requirement in the wein bridge oscillator?

The gain requirement for wein bridge oscillator is minimum 3.

9. Write down the advantages of RC phase shift oscillator.

a) Simplicity of the circuit.

b) Useful for frequencies in the audio range.

c) A sine wave output can be obtained.

10. Write down disadvantages of RC phase shift oscillator.

Poor frequency stability.

It is difficult to get a variable frequency output, because to change

the frequency, we need to vary all the resistors and capacitors simultaneously

which is practically very difficult.

11. Give the comparison between RC and LC oscillators.

S.NO RC oscillators LC oscillators

1. Frequency of oscillations is Frequency of oscillations is dependent on

dependent on values of R and C values of L and C

2. These are used at low and These are preferred at high frequencies

medium frequencies

12.Write down the general applications of oscillators.

a) As a local oscillator in radio receivers.

b) In T.V receivers.

c) In signal generators.

d) As clock generation for logic circuits.


e) AM and FM transmitters.

f) In phase lock loops.

13. Name two high frequency Oscillators.

i. Hartley Oscillator ii. Colpitts Oscillator iii. iii. Crystal Oscillator

14.What are the types of feedback oscillators?

a) RC-Phase shift Oscillator,

b) LC-Oscillators

Tuned collector Oscillator

Tuned emitter Oscillator

Tuned collector base Oscillator

Hartley Oscillator

Colpits Oscillator

Clap Oscillator

15.What are the conditions for oscillation?

The total phase shift of an oscillator should be 360o. For feedback oscillator it

should satisfies Barhausen criterion.

16. Define Piezoelectric effect.

When applying mechanical energy to some type of crystals called piezoelectric

crystals the mechanical energy is converted into electrical energy is called

piezoelectric effect.

17. What is the necessary condition for a wein bridge oscillator to have sustained

oscillations?

In Wein Bridge oscillator gain of the amplifier must be atleast 3 for oscillation to start. And the

phase shift of feedback circuit must be 0 degree as it used as non inverting amplifier.

18. In a RC Phase shift oscillator, if R1=R2=R3=200 KΩ and c1=c2=c3=100pf find the

frequency of the oscillator.

f= 1/ 2πRC= 7.957khz.

19. In an RC phase shift oscillator ,if its frequency of oscillation is 955 Hz and

R1=R2=R3=680KΩ, find the value of capacitors.

f= 1/ 2πRC 955=1/2π*680*10^3*c

c=0.245nF

20. A parallel resonant circuit has an inductance if 150µH and capacitance of 150 Pf find

the resonant frequency.

fp= 1/2π√LCeq= 1/2π√150*10^-6*100*10^-12=1.3MHz.


Ex.No.03

HARTLEY OSCILLATOR & COLPITTS OSCILLATOR Date:

A. HARTLEY OSCILLATOR

OBJECTIVE

To design, construct a Hartley Oscillator using BJT for a desired frequency of oscillation and to observe its

output waveform

EQUIPMENT



THEORY

Hartley oscillator was invented in 1915 by the american engineer Ralph Hartley while he was working for

the Western Electric company. The original design was tube based and he got a patent for it in the year

1920.

In a Hartley oscillator the oscillation frequency is determined by a tank circuit comprising of two inductors

and one capacitor. The inductors are connected in series and the capacitor is connected across them in

parallel. Hartley oscillators are commonly used in radio frequency (RF) oscillator applications and the

recommended frequency range is from 20KHz to 30MHz. Hartley oscillators can be operated at frequencies

lower than 20KHz, but for lower frequencies the inductor value need to be high and it has a practical limit.

The circuit diagram of a typical Hartley oscillator is shown in the figure.

In the circuit diagram resistors R1 and R2 give a potential divider bias for the transistor Q1. Re is the

emitter resistor, whose job is to provide thermal stability for the transistor. CE is the emitter by pass

capacitors, which by-passes the amplified AC signals. If the emitter by-pass capacitor not there, the

amplified ac voltages will drop across Re and it will get added on to the base-emitter voltage of Q1 and will

disrupt the biasing conditions. Cin is the input DC decoupling capacitor while Cout is the output DC

decoupling capacitor. The task of a DC decoupling capacitor is to prevent DC voltages from reaching the

succeeding stage. Inductor L1, L2 and capacitor C1 forms the tank circuit.

When the power supply is switched ON the transistor starts conducting and the collector current increases.

As a result the capacitor C1 starts charging and when the capacitor C1 is fully charged it starts

discharging through coil L1. This charging and discharging creates a series of damped oscillations in the

tank circuit and it is the key.

The oscillations produced in the tank circuit is coupled (fed back) to the base of Q1 and it appears in the

amplified form across the collector and emitter of the transistor. The output voltage of the transistor

(voltage across collector and emitter) will be in phase with the voltage across inductor L1. Since the

junction of two inductors is grounded, the voltage across L2 will be 180° out of phase to that of the voltage

across L1. The voltage across L2 is actually fed back to the base of Q1. From this we can see that, the feed

back voltage is 180° out of phase with the transistor and also the transistor itself will create another 180°

phase difference. So the total phase difference between input and output is 360° and it is very important

condition for creating sustained oscillations.

The frequency “F” of a Hartley oscillator can be expressed using the equation;

C is the capacitance of the capacitor C1 in the tank circuit.

L = L1+L2, the effective series inductance of the inductors L1 and L2 in the tank circuit.

Here the coils L1 and L2 are assumed to be winded on different cores. If they are winded on a single

core then L=L1+L2+2M where M is the mutual inductance between the two coils.

CIRCUIT DIAGRAM


http://www.circuitstoday.com/wp-content/uploads/2009/10/hartley-oscillator-frequency.png

PIN SPECIFICATION OF SL100

DESIGN

VCC = 12V, IC = 1mA

Transistor SL100

Typical values: VCE = 3V; VRE = 3.5V






=


=

𝑉𝑅𝐸


Let RE be RE = 1KΩ + RE1 = 2.5KΩ(Pot.) adjustable to obtain sustained oscillations



I2 = 𝐼𝑐10

=



=

Selection of C1, C2 & CE

Choose C1 = 0.1μf & C2 = CE = 0.01μF

PROCEDURE

1. Connect the circuit as shown in figure.

2. Connect the CRO across the output terminals of the oscillator.

3. Switch on the power supply to both the oscillator and CRO.

4. Select proper values of C, L1 and L2 in the oscillator circuit to obtain the sine waveform on the

screen of CRO. Adjust the Potentiometer to get undistorted output.

5. Observe and measure the peak-to-peak amplitude and time period(T) of the output signal and record the

values in the tabulation provided. The reciprocal of T gives the frequency of the observed waveform


TABULATION

Capacitance

C(µF)

Inductance(mH)

Time period

T

Frequency (Hz)

L1 L2 L=L1+L2 f = 1

𝑇


MODEL GRAPH

RESULT

The BJT version of Hartley oscillator for the given frequency is designed, constructed and the output signal

is observed.

Theoretical fo =

Observed fo =

B. COLPITTS OSCILLATOR

OBJECTIVE

To design, construct a Colpitts Oscillator using BJT for a desired frequency of oscillation and to observe its

output waveform

EQUIPMENT


THEORY


Colpitts oscillator was invented by American scientist Edwin Colpitts in 1918. It is another type of

sinusoidal LC oscillator which has a lot of applications. The Colpitts oscillator can be realized using valves,

transistors, FETs or op-amp. It is much similar to the Hartley oscillator except tank circuit. In Colpitts

oscillator the tank circuit consists of two capacitors in series and an inductor connected in parallel to the

serial combination. The frequency of the oscillations are determined by the value of the capcitors and

inductor in the tank circuit.

Collpitts oscillator is generally used in RF applications and the typical operating range is 20KHz to

300MHz. In Colpitts oscillator, the capacitive voltage divider setup in the tank circuit works as the feed

back source and this arrangement gives better frequency stability when compared to the Hartley oscillator

which uses an inductive voltage divider setup for feedback.

In the circuit diagram resistors R1 and R2 gives a voltage divider biasing to the transistor. Resistor R4

limits the collector current of the transistor. Cin is the input DC decoupling capacitor while Cout is the

output decoupling capacitor. Re is the emitter resistor and its meant for thermal stability. Ce is the emitter

by-pass capacitor. Job of the emitter by-pass capacitor is to by-pass the amplified AC signals from dropping

across Re. The the emitter by-pass capacitor is not there, the amplified AC signal will drop across Re and it

will alter the DC biasing conditions of the transistor and the result will be reduced gain. Capacitors C1, C2

and inductor L1 forms the tank circuit. Feedback to the base of transistor is taken from the junction of

Capacitor C2 and inductor L1 in the tank circuit.

When power supply is switched ON, capacitors C1 and C2 starts charging. When they are fully charged

they starts discharging through the inductor L1. When the capacitors are fully discharged, the electrostatic

energy stored in the capacitors gets transferred to the inductor as magnetic flux. The the inductor starts

discharging and capacitors gets charged again. This transfer of energy back and forth between capacitors

and inductor is the basis of oscillation. Voltage across C2 is phase opposite to that of the voltage across the

C1 and it is the voltage across C2 that is fed back to the transistor. The feedback signal at the base base of

transistor appears in the amplified form across the collector and emitter of the transistor.

The energy lost in the tank circuit is compensated by the transistor and the oscillations are sustained. The

tank circuit produces 180° phase shift and the transistor itself produces another 180° phase shift. That

means the input and output are in phase and it is a necessary condition of positive feedback for maintaining

sustained oscillations. The frequency of oscillations of the Colpitts oscillator can be determined using the

equation below.

Where L is the inductance of the inductor in the tank circuit and C is the effective

capacitance of the capacitors in the tank circuit. If C1 and C2 are the individual capacitance, then the

effective capacitance of the serial combination C= (C1C2)/(C1+C2). By using ganged variable capacitors in

place of C1 and C2, the Colpitts oscillator can be made variable.

CIRCUIT DIAGRAM


http://www.circuitstoday.com/wp-content/uploads/2009/10/colpitts-oscillator-frequency-equation.png

PIN SPECIFICATION OF SL100

DESIGN

VCC = 12V, IC = 1mA

Transistor SL100

Typical values: VCE = 3V; VRE = 3.5V





=



=

𝑉𝑅𝐸


Let RE be RE = 1KΩ + RE1 = 2.5KΩ(Pot.) adjustable to obtain sustained oscillations



I2 = 𝐼𝑐10

=



=

Selection of C1, C2 & CE

Choose C1 = C2 = CE = 0.1μF

PROCEDURE




4. Select proper values of L, C1 and C2 in the oscillator circuit to obtain the sine waveform on the

screen of CRO. Adjust the Potentiometer to get undistorted output. 5. Observe and measure the peak-to-peak amplitude and time period(T) of the output signal and record the

values in the tabulation provided. The reciprocal of T gives the frequency of the observed waveform


TABULATION

Inductance

L(mH)

Capacitance

C(µF) Time period

T

Frequency (Hz)

C1 C2 C= C1|| C2 f = 1

𝑇

MODEL GRAPH


RESULT

The BJT version of Colpitts oscillator for the given frequency is designed, constructed and the output signal

is observed.

Theoretical fo =

Observed fo =

Viva - Questions

1.How to obtain Hartley oscillator from the basic form of LC oscillator?


Using X1 and X2 as inductors and X3 as capacitor, Hartley oscillator from basic form of LC

oscillator is obtained.

2. How to obtained colpitt’s oscillator form basic form of LC oscillator?

Using X1 and X2 as capacitors and X3 as inductors, colpitt’s oscillator from basic form of

LC oscillator is obtained.

3. Write down the advantages, disadvantages and applications of

colpitt’s oscillator.

Advantages:

a) Simple construction.

b) It is possible to obtain oscillations at very high frequencies.

Disadvantages:

a) It is difficult to adjust the feedback as it demands change in capacitor values.

b) Poor frequency stability.

Application:

a) As a high frequency generator.

4. Write down the general applications of oscillators.

g) As a local oscillator in radio receivers.

h) In T.V receivers.

i) In signal generators.

j) As clock generation for logic circuits.

k) AM and FM transmitters.

l) In phase lock loops.

5. What are the conditions for oscillation?

The total phase shift of an oscillator should be 360o. For feedback oscillator it


6. Define Piezoelectric effect.

When applying mechanical energy to some type of crystals called piezoelectric

crystals the mechanical energy is converted into electrical energy is called

piezoelectric effect.

7. Draw the equivalent circuit of crystal oscillator.

8. What are th classifications of Oscillators? Based on wavegenerated:

i. Sinusoidal Oscillator,

ii. Non-sinusoidal Oscillator or Relaxation Oscillator

Ex: Square wave, Triangular wave, Rectangular wave etc.

According to principle involved:


i. Negative resistance Oscillator,

ii. Feedback Oscillator.

9. Differentiate oscillator and amplifier.

AMPLIFIER OSILLATOR

Use negative feed back Uses positive feedback

Requires input to produce output Does not require any input to produce

output

Produces output of similar type as that of

the input with higher power level.

Produces oscillations at the output with

constant amplitude and constant desired

frequency.

10.What is piezo electric effect?

The piezo electric Crystals exhibit a property that if a mechanical stress is applied across one

face the electric potential is developed across opposite face. The inverse is also live. This

phenomenon is called piezo electric effect.

11.List the disadvantages of crystal Oscillator.

It is suitable for only low power circuits

Large amplitude of vibrations may crack the crystal.

It large in frequency is only possible replacing the crystal with another one by different

frequency.

12.What are parasitic Oscillators?

In a practical amplifier circuit due to stray capacitances and lead inductances, oscillations

result, since the circuit conditions satisfy the Barkhavsen’s criterion. These Oscillators are

called as unwanted or parasitic Oscillations

13.What is damped Oscillation?

The electrical Oscillations in which the amplitude decreases with time are called as damped

Oscillation.

14.What are the types of sinusoidal oscillator? Mention the different types of sinusoidal

oscillator?

RC phase shift Oscillator. Wein bridge

Oscillator. Hartley Oscillator Colpitts

Oscillator Crystal Oscillator

15.What is Barkhausan criterion?

The conditions for oscillator to produce oscillation is given by Barkhausan

criterion. They are :

(i). The total phase shift produced by the circuit should be 360o or 0o (ii).The

Magnitude of loop gain must be greater than or equal to 1

i.e. . A׀β1≤ ׀.

16. Name two high frequency Oscillators.

iv. Hartley Oscillator

ii. Colpitts Oscillator iii.Crystal Oscillator


17. What are the essential parts of an Oscillator?

i. Tank circuit (or) Oscillatory circuit.

ii. Amplifier (Transistor amplifier)

iii. Feedback Circuit.

18. Define gain bandwidth product of a tuned amplifier.

A gain band width product of a tuned amplifier is defined as product of 3 db band width and gain

at response of the tuned amplifier.


Every resistance has some free electrons. Under the influence of room temperature, these free

electrons move randomly in various directions. In such a movement of the free electrons

generate a voltage called noise voltage, across the resistance. Such noise voltage provides the

starting voltage for the oscillator.

20. Why in practice A β is kept greater than unity.

To amplify small noise voltage present, so that oscillations can start, A β is kept initially greater

than unity.

Ex.No.04 SINGLE TUNED AMPLIFIER


Date:

OBJECTIVE

To design and construct a single tuned amplifier and obtain its frequency response

EQUIPMENT


THEORY

A tuned amplifier uses a tuned circuit i.e. circuit that selects a particular band of frequencies. A

tuned amplifier has a tuned or resonance circuit passes only a relatively narrow band of frequencies. The

center of this frequency is the resonance frequency of the tuned Circuit . The modulated signal has a

relatively narrow band of frequencies centered around the carrier frequency.

This circuit selects and amplifies only a narrow band of frequencies and rejects or suppress all

frequencies outside this band . The tuned circuit in the output presents a large output load impedance at its

tuned frequency and a low impedance at all other frequencies . Since the amplitude of the output signal

depends on the value of the output impedance , large outputs are developed only at tuned frequency. In the

fig. resistors R1 and R2 provide the voltage divider bias and stabilize the operating point . The tuned circuit

consists of an inductor and capacitor . The inductor is the primary of the transformer . Either L or C , or

both , are made variable so that the resonant frequency of the circuit can be changed . The voltage gain of

an amplifier depends on the output impedance (on the impedance of the tuned circuit) . At resonance , this

impedance is maximum and is resistive . Hence , at this frequency fr , the voltage gain will be maximum but

, as we move away from fr on either side , the impedance and hence , the voltage gain decreases.

.

CIRCUIT DIAGRAM



DESIGN

VCC = 10V, IC = 1mA


Typical values: VRE = 10% of VCC = 1V

Frequency of resonance fr = 5KHz

Tank Circuit

Selection of L & C

fr = 1

2𝜋√𝐿𝐶

Given fr = 5KHz. Assume C = 0.1μF


L = 14∗𝜋∗𝜋∗𝑓𝑟∗𝑓𝑟∗𝐶

=

Selection of RE, R1 & R2


=

𝑉𝑅𝐸


R2 = VR2

𝐼2

I2 = 𝐼𝑐10

=

VR2 = VB = VBE + VRE = (VBE = 0.7V for Si Transistor)

Now, R2 = VR2

𝐼2 =


=

Selection of C1 , C2 & CE

Choose C1 = C2 = 0.1μF

XCE = RE at f1 ; f1 = lower cutoff frequency = 20Hz


= RE

CE = 12𝜋 𝑓1 RE

=

PROCEDURE 1. Connect the circuit as shown in the figure.

2. Connect a sine- wave generator set at 1000Hz frequency and 50mV (p-p) signal voltage at the input of the amplifier circuit.

3. Connect an oscilloscope across the output nodes. Observe the sine wave output on the oscilloscope. Adjust the output of the sine-wave generator until undistorted. Maximum signal output is obtained.

4. Observe and measure the peak-to-peak amplitude of input and output signal and record the values in the tabulation provided.

5. Now, sweep the input signal frequency in the range 30HZ to 1 MHZ by adjusting the sine wave generator output.

6. For each setting of input frequency, measure and record the output signal voltage.

7. Draw the frequency response curve on a semi-log graph sheet. From this plot, obtain the values of resonant frequency, upper and lower cut-off frequency and BW.


TABULATION

Frequency Response

Input Voltage Vi =

Frequency f

(Hz)

Output Voltage Vo

(V) Gain Av =

𝑽𝒐

𝑽𝒊

Gain in dB

20 log Av

MODEL GRAPH

RESULT

Single tuned amplifier is designed, constructed and its frequency response is plotted. The tuned frequency is observed

Theoretical (fT) : Practical (fP) : Quality factor (Q) (fo/BW) :


Viva - Questions

1. What do you mean by tuned amplifiers?

The amplifiers which amplify only selected range of frequencies (narrow band of frequencies)

with the help of tuned circuits (parallel LC circuit) are called tuned amplifiers.

2. What are the various types of tuned amplifiers?

1)Small signal tuned amplifiers

a. Single tuned amplifiers

(i) Capacitive coupled

Inductively coupled (or) Transformer coupled

b. Double tuned amplifiers

c. Stagger tuned amplifiers

2)Large signal tuned amplifiers

3. Give the expressions for the resonance frequency and impedance of the tuned

circuit.

f r

=

1

& Z R =

L

2

π

C

R

L

C

4. What is the response of tuned amplifiers?

The response of tuned amplifier is maximum at resonant frequency and it falls sharply for

frequencies below and above the resonant frequency.

5. When tuned circuit is like resistive, capacitive and inductive?

At resonance, circuit is like resistive.

For frequencies above resonance, circuit is like capacitive.

For frequencies below resonance, circuit is like inductive.

6. What are the various components of coil losses?

Copper loss

Eddy current loss

Hysteresis loss

7. Define Q factor of resonant circuit.

It is the ratio of reactance to resistance.

It also can be defined as the measure of efficiency with which inductor can store the energy.

Q=2п *(Maximum Energy Stored per cycle / Energy dissipated per cycle)

8. What is dissipation factor?

It is defined as 1/Q.

It can be referred to as the total loss within a component.

9. Define unloaded and loaded Q of tuned circuit.

The unloaded Q or QU is the ratio of stored energy to dissipated energy in a reactor or resonator.


10. The loaded Q or QL of a resonator is determined by how tightly the resonator

is coupled to its terminations. Why quality factor is kept as high as possible in tuned

circuits?

1. When Q is high, bandwidth is low and we get better selectivity. Hence Q is kept as high as

possible in tuned circuits.

2. When Q is high inductor losses are less.

11. List various types of cascaded Small signal tuned amplifiers.

1. Single tuned amplifiers.

2. Double tuned amplifiers.

3. Stagger tuned amplifiers.

12. How single tuned amplifiers are classified?

1. Capacitance coupled single tuned amplifier.

2. Transformer coupled or inductively coupled single tuned amplifier.

13. What are single tuned amplifiers?

Single tuned amplifiers use one parallel resonant circuit as the load impedance in each

stage and all the tuned circuits are tuned to the same frequency.

14. What are double tuned amplifiers?

Double tuned amplifiers use two inductively coupled tuned circuits per stage, both the tuned

circuits being tuned to the same frequency.

15. What are stagger tuned amplifiers?

Stagger tuned amplifiers use a number of single tuned stages in cascade, the successive tuned

circuits being tuned to slightly different frequencies.

16. What is the effect of cascading single tuned amplifiers on bandwidth? Bandwidth reduces due to cascading single tuned amplifiers.

17. List the advantages and disadvantages of tuned amplifiers.

Advantages:

1. They amplify defined frequencies.

2. Signal to Noise ratio at output is good.

Disadvantages:

1. Since they use inductors and capacitors as tuning elements, the circuit is bulky and costly.

2. If the band of frequency is increased, design becomes complex.

18. What are the advantages of double tuned amplifier over single tuned amplifier?

1. It provides larger 3 dB bandwidth than the single tuned amplifier and hence provides the

larger gain-bandwidth product.

2. It provides gain versus frequency curve having steeper sides and flatter top.

19. What the advantages are of stagger tuned amplifier?

The advantage of stagger tuned amplifier is to have better flat, wideband characteristics.

20. Mention the applications of class C tuned amplifier.

1. Class C amplifiers are used primarily in high-power, high-frequency applications

such as Radio-frequency transmitters.

2. In these applications, the high frequency pulses handled by the amplifier are not themselves

the signal, but constitute what is called the Carrier for the signal.


Ex.No.05 RC INTEGRATOR AND DIFFERNTIATOR CIRCUITS

Date:

OBJECTIVE

To design, construct Integrator and differentiator circuits using simple RC network and study their time

response.

EQUIPMENT


THEORY

A differentiator gives the derivative of input voltage as output. A differentiator using passive

components resistors and capacitors is a high pass filter. The circuit is shown .It acts as a differentiator only

when the time constant is too small. The voltage at output is proportional to the current through the

capacitor. The current through the capacitor can be expressed as C dv/dt. The output is taking across the

resistor. So output will be RC dv/dt. Thus differentiation of input takes place.

When a square wave is applied at the input, during the positive half cycle capacitor charges. So

initially the voltage across the resistor will be the applied voltage. As the capacitor charges, the voltage

across resistor decreases.

Now consider the case of integrator. It is a low pass filter. Here the time constant of the circuit

should be very large. Here output is taking across the capacitor. As the input square wave is applied, during

the positive half cycle the voltage across capacitor increases from zero, to the maximum (peak value of

applied voltage). During the negative half cycle, the capacitor starts to discharge and comes to zero. This

process repeats for the remaining cycles and a triangular wave is obtained.


CIRCUIT DIAGRAM

RC Integrator

RC Differentiator

MODEL GRAPH

RC Integrator RC Differentiator

DESIGN

Select Vin = 5VP-P, 1KHz (both Square & Pulse)

Integrator

For an Integrator, RC ≥ 16T

The frequency of the input signal is 1KHz, then Time period T = 1ms.


In order to avoid loading of the signal, choose the value of R as ten times the output impedance of the

function generator (600Ω).

So, R = 10 x 600Ω = 6KΩ (6.8KΩ Std.)

Therefore, C ≥ 16𝑇

𝑅

≥ 16∗1𝑚𝑠

6.8𝐾

≥ 2.3μF (Use 2.2μF Std.)

Differentiator

For a Differentiator, RC ≤ 0.0016T

The frequency of the input signal is 1KHz, then Time period T = 1ms.

In order to avoid loading of the signal, choose the value of R as ten times the output impedance of the

function generator (600Ω).

So, R = 10 x 600Ω = 6KΩ (6.8KΩ Std.)

Therefore, C ≤ 0.0016𝑇

𝑅

≤ 0.0016∗1𝑚𝑠

6.8𝐾

≤ 235pF (Use 220pF Std.)

PROCEDURE

RC Integrator

1. Connect the Integrator circuit as shown in figure.

2. Connect signal from the OUTPUT socket of the FG to the RC circuit, and also to the CH-1 input of the

CRO.

3. Choose square wave signal and adjust the amplitude control to obtain a 5VP-P, 1KHz

4. Connect the output of the RC circuit to CH-2 input of the CRO. Be sure to choose the DC mode for both

CH-1and CH-2 inputs so as to observe the dc levels of the signals.

i. Time response when T << τ, τ = RC(time constant) :

Choose the waveform frequency (f) to be 5 kHz. Observe and sketch Vi and V0 with respect to

time. Note down the salient features of V0.

ii. Time response when T ≈ τ, τ = RC(time constant) :

Choose f to be 1 kHz. Observe and sketch Vi and V0 with respect to time. Note down the salient

features of V0.

Choose any two convenient points on the rising and falling parts of V0 and measure the

corresponding voltages and the time intervals. From these readings, obtain the time constant of

the circuit. Compare the result with that obtained using the values of the components (R and C)

used in the circuit.

iii. Time response when T > τ, τ = RC(time constant) :

Choose f = 100 Hz. Observe and sketch Vi and V0.


RC Differentiator

1. Connect the differentiator circuit as shown in figure.

2. Connect signal from the OUTPUT socket of the FG to the RC circuit, and also to the CH-1 input of the

CRO.

3. Choose square wave signal and adjust the amplitude control to obtain a 5VP-P, 1KHz.

4. As in the case of the RC integrator circuit, obtain time response of this circuit for the following three

cases. Sketch Vi and V0 for each case.

i. Time response when T << τ, τ = RC(time constant) : Choose f = 5KHz.

ii. Time response when T ≈ τ, τ = RC(time constant) : Choose f = 1KHz.

iii. Time response when T > τ, τ = RC(time constant) : Choose f = 100Hz.

iv. Increase the input signal frequency beyond 8 kHz and note the minimum frequency at which the

linear tilt (droop) seen in the output waveform is negligible.

TABULATION

CIRCUIT

INPUT OUTPUT

AMPLITUDE

(V)

TIME (ms) AMPLITUDE (V) TIME (ms)

INTEGRATOR

DIFFERENTIATOR

RESULT

The RC Integrator and differentiator circuits are designed, constructed using simple RC network and the

time response is studied.


Viva - Questions

1.What is High pass RC circuit? Why it is called high-pass filter?

A simple circuit consisting of a series capacitor and a shunt resistor is called high pass RC

circuit. At very high frequencies the capacitor acts as a short circuit and all the higher frequency

components appear at the output with less attenuation than the lower frequency components.

Hence this circuit is called high-pass circuit.

2.Why high-pass RC circuit is called Differentiator?

High-pass RC circuit gives an output waveform similar to the first derivative of the input

waveform. Hence it is called Differentiator.

3.What is Low pass RC circuit? Why it is called low-pass filter?

A simple circuit consisting of a series resistor and a shunt capacitor is called Low pass RC

circuit. At very high frequencies the capacitor acts as a virtual short circuit and output falls to

zero. Hence this circuit is called low-pass filter

4.Why low-pass RC circuit is called Integrator?

Low pass RC circuit gives an output waveform similar to the time integral of the input

waveform. Hence it is called Integrator.

5.What is High pass RL circuit? Why it is called high-pass filter?

A simple circuit consisting of a series resistor and a shunt inductor is called high-pass RL

circuit. At very high frequencies, the inductor acts as an open circuit and all the higher

frequency components appear at the output. Hence this circuit is called high-pass filter.

6.What is Low pass RL circuit? Why it is called low-pass filter?

A simple circuit consisting of a series inductor and a shunt resistor is called low pass RL

circuit. At very high frequencies, the inductor acts as a virtual open circuit and the output falls

to zero. Hence this circuit is called low pass filter.

7.What is Delay time (td) in transistor?

The time needed for the collector current to rise to 10% of its maximum (saturation)

value i.e. iC(Sat) = VCC/RC is called the delay time.

8.What is Rise time (tr) in transistor?

The time required for the collector current to rise from 10% to 90% of the maximum value is

called rise time (tr).

9.What is Turn-ON time (tON) in transistor?

The sum of the delay time (td) and the rise time (tr) is called the turn-ON time (tON).

tON = td + tr

10. What is storage time (ts) in transistor?

The time when collector current (iC) dropped to 90% of its maximum value is called the

storage time.

11. What is fall time (tf) in transistor?

The time required for the collector current to fall from 90% to 10% of its maximum

value is called fall time (tf).


12. What is Turn-off time (tOFF) in transistor?

The sum of the storage time (ts) and the fall time (tf) is called the turn-OFF

time (tOFF). (tOFF) = (ts) + (tf)

13. Define integrator.

Integrator is a circuit that passes low frequencies of the input and attenuates high frequencies.

Integrator implies that the output voltage is an integral of the input voltage.

14. What is the use of commutating capacitors?

The Commutating capacitors can be used to reduce the transition time in a low to high level and

vice versa.

15. Define transition time.

The time interval during which the conduction transfer from one transistor to another transistor

is defined as transition time.

16. What is delay time?

The time required for the current to rise to 10% of its maximum (saturation) value Ics is called

the delay time td.

17. What is the total turn on time?

The total turn on time is ton is the sum of the delay time and rise time, ton = td

+ tr , Where,td = Delay time. tr = Rise time.

18. What is storage time?

The interval that elapses between the transition of the input waveform and the time when the

collector current has dropped to 90 % of total output is called the storage time ts.

19. Define transition time.

The time interval during which the conduction transfer from one transistor to another transistor is

defined as transition time.

20. Define differentiator. Differentiator is a circuit that passes high frequencies of the input and attenuates low frequencies. It implies that the output voltage is the differential of the input.


Ex.No.06 ASTABLE AND MONOSTABLE MULTIVIBRATORS

Date:

A. ASTABLE MULTIVIBRATOR

OBJECTIVE

To design and construct a Astable multivibrator using BJT and observe its collector and base waveforms

EQUIPMENT


THEORY

Multivibrators are Sequential regenerative circuits either synchronous or asynchronous and are used

extensively in electronic timing applications. Multivibrators produce an output wave shape resembling that

of a symmetrical or asymmetrical square wave and as such are the most commonly used of all the square

wave generators. Multivibrators belong to a family of oscillators commonly called “Relaxation Oscillators“.

Generally speaking, discrete multivibrators consist of a two transistor cross coupled switching circuit

designed so that one or more of its outputs are fed back as an input to the other transistor with a resistor and

capacitor ( RC ) network connected across them to produce the feedback tank circuit.

Transistorized Astable Multivibrator is a cross coupled transistor network capable of producing sharp

continuous square wave. It is free running oscillator or simply a regenerative switching circuit using

positive feedback. Astable Multivibrator switches continuously between its two unstable states without the

need for any external triggering.

Time period of Astable multivibrator can be controlled by changing the values of feedback components

such as coupling capacitors and resistors.

When a transistor is ON, its collector and emitter act as a short circuit. But when it is OFF they acts as open

circuit. So in the above circuit when a transistor is in OFF state its collector will have the voltage Vcc and

when it is ON its collector will be grounded. When one transistor is ON the other will be OFF. The OFF

time of transistor is determined by RC time constant.

When the circuit is switched on, one of the transistor will be more conducting than the other due imbalance

in the circuit or difference in the parameters of the transistor. Gradually the more conducting transistor will

be driven to Saturation and the less conducting transistor will be driven to Cutoff.


http://www.electronics-tutorials.ws/sequential/seq_1.html

CIRCUIT DIAGRAM

DESIGN

VCC = 10V; IC = 2mA


Pulse width T = 1ms; Duty cycle = 1

3

Selection of RC1 & RC2

Take RC1 = RC2 = RC

RC = (𝑉𝐶𝐶−𝑉𝐶𝐸𝑠𝑎𝑡)

𝐼𝐶 = (VCEsat = 0.3V)


The value of R1 & R2 must be selected such that it must be able to provide enough base current to keep

transistors in saturation

IBmin = 𝐼𝑐ℎ𝑓𝑒

=

To ensure the operation of transistor in saturation,

IB = 5 IBmin =

R1 = (𝑉𝐶𝐶−𝑉𝐵𝐸𝑠𝑎𝑡)

𝐼𝐵 = (VBEsat = 0.7V)

Take R1 = R2 =

For stable operation, value of R1 & R2 should be less than hfe RC; Ensure if R1 & R2 are less than hfe RC



Given, pulse width T = TON + TOFF = 1ms & Duty cycle, D = 𝑇𝑂𝑁

𝑇𝑂𝑁+𝑇𝑂𝐹𝐹 =

1

3

TON = D(TON + TOFF) = 1

3(1ms) = 0.333ms

TOFF = T - TON = 1ms – 0.333ms = 0.667ms

TON = 0.693 R1C1

C1 = 𝑇𝑂𝑁

0.693 R1 =

TOFF = 0.693 R2C2

C2 = 𝑇𝑂𝐹𝐹

0.693 R2 =

PROCEDURE




4. Observe and measure the amplitude and time period of the collector and base waveforms on both

transistors and record the values in the tabulation provided.

5. Sketch the waveforms on a graph.

TABULATION

Particulars Amplitude (v) Time Period (ms)

VB1

VC1

VB2

VC2


MODEL GRAPH

RESULT

The Astable Multivibrator using BJT is designed, constructed and the collector and base waveforms are

observed.


B. MONOSTABLE MULTIVIBRATOR

OBJECTIVE

To design and construct a Monostable multivibrator using BJT and observe its collector and base waveforms

EQUIPMENT


THEORY

Monostable Multivibrators or “One-Shot Multivibrators” as they are also called, are used to generate a

single output pulse of a specified width, either “HIGH” or “LOW” when a suitable external trigger signal or

pulse T is applied. This trigger signal initiates a timing cycle which causes the output of the monostable to

change its state at the start of the timing cycle and will remain in this second state.

The timing cycle of the monostable is determined by the time constant of the timing capacitor, CTand the

resistor, RT until it resets or returns itself back to its original (stable) state. The monostable multivibrator

will then remain in this original stable state indefinitely until another input pulse or trigger signal is

received. Then, Monostable Multivibrators have only ONE stable state and go through a full cycle in

response to a single triggering input pulse.

The basic collector-coupled transistor Monostable Multivibrator circuit and its associated waveforms are

shown above. When power is firstly applied, the base of transistor TR2 is connected to Vcc via the biasing

resistor, RT thereby turning the transistor “fully-ON” and into saturation and at the same time

turning TR1 “OFF” in the process. This then represents the circuits “Stable State” with zero output. The

current flowing into the saturated base terminal of TR2 will therefore be equal toIb = (Vcc – 0.7)/RT.

If a negative trigger pulse is now applied at the input, the fast decaying edge of the pulse will pass straight

through capacitor, C1 to the base of transistor, TR1 via the blocking diode turning it “ON”. The collector

of TR1 which was previously at Vcc drops quickly to below zero volts effectively giving capacitor CT a

reverse charge of -0.7v across its plates. This action results in transistor TR2 now having a minus base

voltage at point X holding the transistor fully “OFF”. This then represents the circuits second state, the

“Unstable State” with an output voltage equal to Vcc.

Timing capacitor, CT begins to discharge this -0.7v through the timing resistor RT, attempting to charge up

to the supply voltage Vcc. This negative voltage at the base of transistor TR2 begins to decrease gradually

at a rate determined by the time constant of the RT CT combination. As the base voltage of TR2 increases

back up to Vcc, the transistor begins to conduct and doing so turns “OFF” again transistor TR1 which

results in the monostable multivibrator automatically returning back to its original stable state awaiting a

second negative trigger pulse to restart the process once again.

Monostable Multivibrators can produce a very short pulse or a much longer rectangular shaped waveform

whose leading edge rises in time with the externally applied trigger pulse and whose trailing edge is

dependent upon the RC time constant of the feedback components used. This RCtime constant may be

varied with time to produce a series of pulses which have a controlled fixed time delay in relation to the

original trigger pulse.


CIRCUIT DIAGRAM

DESIGN

VCC = 12V; IC = 2mA; Typical Values: VRE = 2V


Pulse width T = 1.5ms

Selection of RE


=

𝑉𝑅𝐸


Selection of RC1 & RC2

Take RC1 = RC2 = RC

RC = (𝑉𝐶𝐶−𝑉𝐶𝐸𝑠𝑎𝑡−𝑉𝑅𝐸)

𝐼𝐶 = (VCEsat = 0.3V)


Selection of R

The value of R must be selected such that it must be able to provide enough base current to keep transistor,

Q2 in saturation

IBmin = 𝐼𝑐ℎ𝑓𝑒

=

To ensure the operation of transistor in saturation,

IB = 5 IBmin =

RC = (𝑉𝐶𝐶−𝑉𝐵𝐸𝑠𝑎𝑡−𝑉𝑅𝐸)

𝐼𝐵 = (VBEsat = 0.7V)


i) Considering the stable state: Q1 – OFF & Q2 – ON

For ensuring Q1 in OFF state; VBE1 = -1V

Then, VB1 = VR1 = VBE1 + VRE

Since, IB = 0, current through R2 = current through R1

VB1 = 𝑉𝐶1 𝑅2

𝑅1+𝑅2

VC1 = VCEsat + VRE = 0.3 + 2 = 2.3V

VB1 = 2.3 𝑅2

𝑅1+𝑅2

Substituting for VB1, and simplifying we get R2 = 1.3R1

ii) Considering the quasi stable state: Q1 – ON & Q2 – OFF

Since Qs is OFF ; VC2 = 12V

VB1 = VBEsat + VRE = 0.7+2 = 2.7V

Also, IR2 = IB1 + IR1

(𝑉𝐶𝐶−𝑉𝐵1)

𝑅2 = IB +

𝑉𝐵1

𝑅1

Substituting for VB1, IB & R2 = 1.3R1, we obtain R1 =

Then, R2 = 1.3R1 =

Selection of C

Given, T = 0.693RC = 1.5ms

C = 𝑇

0.693𝑅 =

Selection of speed up capacitor, C1

C1 R2 = Cπ R1

Where, Cπ => base emitter capacitance of Q1 (Cπ = 12pF from datasheet)

C1 = Cπ R1

𝑅2 =

Design of triggering (differentiator) circuit

Condition to be satisfied, Rd Cd ≤ 0.0016Tt; Tt = 2ms

Take Rd = 6.8KΩ

Cd ≤ 0.0016 𝑇𝑡

𝑅𝑑 =


PROCEDURE




4. Observe and measure the amplitude and time period of the collector and base waveforms on both

transistors and record the values in the tabulation provided.

5. Sketch the waveforms on a graph.

TABULATION

Particulars Amplitude(v) Time Period(ms)

Trigger

VB1

VC1

VB2

VC2

MODEL GRAPH

RESULT

The Monostable Multivibrator using BJT is designed, constructed and the collector and base waveforms are

observed.


Viva - Questions

1. Define the Bistable multivibrator.

Bistable multivibrator signifies a circuit which can exist indefinitely in either of two stable states

and which can be induced to make an abrupt transition from one state to other by applying an

external triggering signal.

2. Define resolving time.

It is the minimum time interval between two consecutive trigger pulses and equals to transition

time plus the settling time.

4. What are different types of triggering of bistable multivibrator?

Asymmetrical triggering.

Symmetrical triggering.

5. What is a linear waveform-shaping circuit?

The process by which the shape of a nonsinusoidal signal is changed by passing the signal

through the network consisting of linear elements is called Linear Wave Shaping.

6. What is meant by multivibrator?

Multivibrators are two stage switching circuits in which the output of the first stage is fed to the

input of the second state and vice-versa. The outputs of two stages are complementary.

7. Define Astable multivibrator.

Astable multivibrator is a multivibrator in which neither state is stable. There are two temporary

states. The circuit changes state continuously from one quasi stables state to another at regular

intervals without any triggering. This generates continuous square waveform without any

external signal.

8. Define monostable multivibrator.

When a trigger pulse is applied to the input circuit, the circuit state is changed abruptly to

unstable state for a predetermined time after which the circuit returned to its original stable state

automatically.

9. Which circuits are called multivibrators?

The electronic circuits which are used to generate nonsinusoidal waveforms are called

multivibrators.

They are two stage switching circuits in which the output of the first stage is fed to the

input of the second stage and vice-versa.

10.Which are the various types of multivibrators?

Astable multivibrator

Bistablemultivibrator

Monostable multivibrator

11. What is astablemultivibrator?

A multivibrator which generates square wave without any external triggering

pulse is called astablemultivibrator.

It has both the states as quasi-stable states. None of the states is stable.

12. List the applications of Astable multivibrator?

Used as square wave generator,.

production of harmonic frequencies of higher order.

Construction of digital voltmeter and SMPS.


13.State the basic action of monostablemultivibrator.

It has only one stable state. The other state is unstable referred as quasi-stable state.It is

also known as one-short multivibrator or univibrator.

When an external trigger pulse is applied to the circuit, the circuit goes into the quasi-

stable state from its normal stable state.After some time interval, the circuit

automatically returns to its stable state.

14. Mention the applications of one short multivibrator?

It is used to function as an adjustable pulse width generator.

It is used to generate uniform width pulses from a variable width pulse train.

It is used to generate clean and sharp pulses from the distorted pulses.

It is used as a time delay unit since it produces a transition at a fixed time after the trigger

signal.

15.Which multivibrator would function as a time delay unit? Why?

Monostable multivibrator would function as a time delay unit since it produces a transition at

a fixed time after the trigger signal.

16.What is Bistablemultivibrator?

The Bistablemultivibrator has two stable states.

The multivibrator can exist indefinitely in either of the two stable states.

It requires an external trigger pulse to change from one stable state to another.

The circuit remains in one stable state unless an external trigger pulse is applied.

17.List the applications of bistable multivibrator?

It is used as memory elements in shift registers, counters, and so on.

It is used to generate square waves of symmetrical shape by sending regular triggering pulse

to the input. By adjusting the frequency of the trigger pulse, the width of the square wave can

be altered.

It can also be used as a frequency divider.

18.What are the two methods of triggering for bistablemultivibrators?

Unsymmetrical triggering

Symmetrical triggering

19.How many stable states do bistableMultivibrator have?

Two stable states.

20.When will the circuit change from stable state in bistable Multivibrator?

When an external trigger pulse is applied, the circuit changes from one stable state to

another.


Ex.No.07 CLIPPERS AND CLAMPERS

Date:

A. CLIPPERS

OBJECTIVE

To construct, study various Clipping circuits and observe their output waveforms.

EQUIPMENT


THEORY

Diode clipper Circuits

A clipper is a circuit in which the output of an input sinusoidal (or any time-dependent signal)

waveform can be clipped at different levels. A clipping circuit requires at least two fundamental

components, a diode and a resistor. A DC battery, however, is also frequently used. The output

waveform can be clipped at different levels simply by interchanging the position of the various

elements and changing the magnitude of the DC battery. Generally, ideal diodes are considered

and the complete analysis can be based on non-ideal diodes with specific V-I characteristic.

For networks of this type, it is often helpful to consider particular instants of the time-varying input

signal to determine the state of the diode (ON or OFF). Keep in mind that even the though input

varies, at a specific time instant this time varying signal can be replaced by a DC source of the

same value. Error! Reference source not found.Examples of various clipping circuits are shown

below. Note that the input to all circuits is a sinusoidal waveform.


CIRCUIT DIAGRAM – PART I: IDEAL CLIPPING CIRCUITS

VR

inV

out

+

-

+

-V

V

V

t

out

VR

inV

out

+

-

+

-V

V

V

t

out

Clipping circuits

For two circuits on the left, the maximum output voltage is clipped at Vout = V. (Ideal diode)

For two circuits on the right the minimum output voltage is clipped at Vout= V. (Ideal diode)

For a non-ideal diode, maximum or minimum output voltage is Vout = V + Vd, or –V - Vd where Vd is the

voltage drop across the diode.

Circuit 1

Positive Clipper

VB = +V

Circuit 2

Negative Clipper

VB = +V


PROCEDURE

PART I: IDEAL CLIPPING CIRCUITS (Circuit 1 & 2)

NOTE: Set Vin = 8VP-P at 1kHz with 0V DC offset and R = 1kΩ for all circuits.

1. Connect the circuit shown in Figure.

2. Set voltage VB to 0V using the Variable Power Supply (VPS) front panel.

3. Measure Vin and Vo using the oscilloscope. Make an accurate sketch of the input and output

waveforms on the same graph, making note of the peak values of Vo (minimum Vo and maximum Vo) and

the input voltage at which clipping occurs.

4. Set VB = 2V and repeat step (3).

5. Sketch the input and output waveforms.

6. Record the voltage at which clipping occurs.

CIRCUIT DIAGRAM – PART II: SERIES – BIASED CLIPPER

PART II: SERIES-BIASED CLIPPING CIRCUITS (Circuit 3

NOTE: The Function Generator (FGEN) in the following circuits will provide both the VSIN and VB voltages.

DO NOT USE SUPPLY+ OR SUPPLY–(RPS) IN THE CIRCUITS.

R = 1kΩ for all circuits.

1. Connect the circuit shown in Figure 4.6(a) using the function generator to supply both VSIN and VB. Set

the AMPLITUDE voltage to 8VP-P. Set the frequency to 1kHz. Set the DC offset to 0V.

2. Measure VSIN and Vo using the oscilloscope using SCOPE CH0 and CH1, respectively. Set the coupling

on CH0 and CH1 to DC. Click “Autoscale”. Make an accurate sketch of VSIN and Vo on the same graph,

making note of the peak values of Vo (minimum Vo and maximum Vo) and the value of VSIN at which

clipping occurs. Use the cursors as needed.

3. Set the DC offset of the function generator to 2V (which is same as VB=2V) and repeat step(2).



Circuit 3

Series biased Clipper


PART III: PARALLEL-BIASED CLIPPER (Circuit 4)

It is possible to clip wave forms at two different voltages. The circuit shown in Figure clips the waveform

ideally at VB1 (SUPPLY+ = 2V) and VB2 (SUPPLY– = –2V).

1. Connect the circuit shown in Figure using the function generator to supply both VSIN and VB. Set the

AMPLITUDE voltage to 8VP-P. Set the frequency to 1kHz. Set the DC offset to 0V.

2. Measure VSIN and Vo using the oscilloscope using SCOPE CH0 and CH1, respectively.

3. Make an accurate sketch of the input and output voltage waveforms for the circuit in Figure, noting the

peaks of the output waveform and the input voltage at which clipping occurs.



CIRCUIT DIAGRAM – PART III: PARALLEL – BIASED CLIPPER

TABULATION

Particulars Input Output

Amp (V) Time (ms) Amp (V) Time (ms)

Ideal Clipping Circuits

Circuit 1

Circuit 2

Series – Biased Clipping Circuit

Circuit 3

Parallel – Biased Clipping Circuits

Circuit 4

RESULT

The various Diode Clipping circuits are constructed and their output waveforms are observed.

Circuit 4

Parallel

Biased

Clipper


B. CLAMPERS

OBJECTIVE

To construct, study various Clamping circuits and observe their output waveforms.

EQUIPMENT


THEORY

Diode clamper circuits

A clamper is a circuit which will add or subtract a DC component from any input voltage. The

clamping circuit has a minimum requirement of three elements: a diode, a capacitor, and a resistor.

The clamping circuit may also include a DC battery. The magnitude of R and C must be chosen

such that the time constant = R·C is large enough to ensure that the voltage across the capacitor

does not change significantly during the interval of time, determined by the input, that both R and

C affect the output waveform. It is usually advantageous when examining clamping circuits to first

consider the conditions that exist when the input is such that the diode is forward-biased. Error!

Reference source not found.shows examples of various clamping circuits and their output

waveforms. Note that the input is a square wave with peak-to-peak value of 2V. The peak-to-peak

value of all the output waveforms is always 2V but the waveforms are shifted depending on the dc-

biasing of the circuits.


CIRCUIT DIAGRAM

VRin

Vout

+

-

+

-

C

V

V

t

out

V

VRin

Vout

+

-

+

-

C

V

V

t

out

V

Clamping circuits

DESIGN

Assume C, and for clamping to occur, select R such that RC>>T where T is the period of input signal

RC>>T, Assume T = 2ms

Let RC = 50T = 100 ms

Let R = 100KΩ, => C = 1µF

Positive Peak Clamper(Positive Reference)

Assume Vin = 10VP-P, VR = 2V, VD = 0.6V

a. During the positive half of the input signal, diode D is forward biased, therefore D = ON

Applying KVL to the loop

Vin – VC – VD – VR = 0

VC = Vin – VD – VR


VC = 5 – 0.6 – 2

VC = 2.4V

b. During the negative half of the input signal, diode D is reverse biased, therefore D = OFF


Vin – VC – Vo = 0

Vo = Vin – VC

When Vin = 0V, Vo = -2.4V

Vin = 5V, Vo = 2.6V

Vin = -5V, Vo = -7.4V

The output varies between 2.6V and -7.4V

Negative Peak Clamper(Negative Reference)

Assume Vin = 10VP-P, VR = 2V, VD = 0.6V

a. During the negative half of the input signal, diode D is forward biased, therefore D = ON


-Vin + VC + VD + VR = 0

VC = -(-Vin + VD + VR)

VC =-(- 5 + 0.6 + 2)

VC = 2.4V

b. During the positive half of the input signal, diode D is reverse biased, therefore D = OFF


Vin + VC – Vo = 0

Vo = Vin + VC

When Vin = 0V, Vo = 2.4V

Vin = 5V, Vo = 7.4V

Vin = -5V, Vo = -2.6V

The output varies between -2.6V and 7.4V

CIRCUIT DIAGRAM

Particulars Input Output

Amp (V) Time (ms) Amp (V) Time (ms)

Positive peak Clamper

Negative peak Clamper


PROCEDURE

1. Build the circuit shown in figure.

2. Measure Vin and Vo using the oscilloscope using SCOPE CH0 and CH1, respectively. Set the coupling

of both oscilloscope channels to DC.

3. Make an accurate sketch of the input and output waveforms for a 8VP-P sine wave input voltage for each

of the circuit.

4. Record the Values.

RESULT

The various Diode Clamping circuits are constructed and their output waveforms are observed.


Viva - Questions

1. What is clipper?

The circuit with which the waveform is shaped by removing (or clipping) a portion

of the input signal without distorting the remaining part of the alternating waveform is

called a clipper.

2.What are the four categories of clippers?

Positive clipper

Negative clipper

Biased clipper

Combination clipper

3. What is comparator?

The nonlinear circuit which was used to perform the operation of clipping may also be

used to perform the operation of comparison is called the comparator.

The comparator circuit compares an input signal with a reference voltage.

4. What is clamper?

A circuit which shifts (clamps) a signal to a different dc level, i.e. which introduces a dc

level to an ac signal is called clamper. It is also called dc restorer.

5. Why does one of the transistor start conducting ahead of other?

The characteristic of both the transistors are never identical hence after giving supplies one of the

Transistors start conducting ahead of the other.

6. What is feed back?

It is the process of injecting some energy from the output and then returns it back tothe

input.

7. What is the disadvantage of negative feed back?

Reduces amplifier gain.

8. Define sensitivity.

It is the ratio of percentage change in voltage gain with feedback to the percentage change in

voltage gain without feed back.

9. Define Desensitivity.

It is the ratio of percentage change in voltage gain without feedback to the percentage change

in voltage.

10. What is delay time? The time required for the current to rise to 10% of its maximum (saturation) value Ics is called the delay time td. 11. What is the total turn on time? The total turn on time is ton is the sum of the delay time and rise time, ton = td + tr;Where,td = Delay time. Tr = Rise time.

12.What is storage time? The interval that elapses between the transition of the input waveform and the time when the collector current has dropped to 90 % of total output is called the storage time ts.


13.Define transition time. The time interval during which the conduction transfer from one transistor to another transistor is defined as transition time. 14. Define resolving time. The smallest allowable interval between triggers is called resolving time. 15. Give the expression of fmax with respect to resolving time. Fmax = 1/resolving time. 16. Define gate width. The pulse width is the time for which the circuit remains in the quasi stable state. It is also called gate width. 17. What is UTP of the Schmitt Trigger? The level of Vi at which Q1 becomes ON and Q2 OFF is called Upper Threshold Point. 18. What is the other name for UTP? It is also called input turn on threshold level. 19. Define transfer Characteristics of Schmitt trigger. The graph of output voltage against input voltage is called transfer characteristics of Schmitt trigger. 20. Define Duty cycle.

The duty cycle is defined as the ratio of the ON time tp to the time period T. Mathematically it is given by, D= tp/T


Ex.No.08 BLOCKING OSCILLATOR

Date:

OBJECTIVE

To observe the characteristics of blocking oscillator. EQUIPMENT


THEORY

A blocking oscillator is the minimal configuration of discrete electronic components which can

produce a free-running signal, requiring only a capacitor, transformer an one amplifying component. The

name is derived from the fact that the transistor is cut-off or blocked for most of the duty cycle, producing

periodic pulses. The non-sinusoidal output is not suitable for use as a radio frequency local oscillator, but it

can serve to flash lights or LEDs, and the simple tones are sufficient for applications such as alarms or a

morse-code practice device. Some cameras use a blocking oscillator to strobe the flash prior to a shot to

reduce the red-eye effect.

Due to the simplicity of the circuit, it forms the basis for many of the learning projects in commercial

electronic kits. A secondary winding of the transformer can be fed to a speaker, a lamp, or the windings of a

relay. Potentiometer placed in parallel with the timing capacitor permits the frequency to be adjusted, but at

low resistances the transistor will be overdriven, and possibly damaged. The output signal will jump in

amplitude and be greatly distorted. The frequency of the oscillator is also affected by the supply voltage.


CIRCUIT DIAGRAM

MODEL GRAPH

PROCEDURE






RESULT

The BJT version of Free running blocking oscillator is constructed and the output signal is observed.


Viva - Questions

1.Write the equation for finding the bandwidth.

Bandwidth= f2-f1

Where f1= lower cut off frequency and f2= higher cut off frequency

2.What is blocking oscillator?

The circuit which uses a regerative feedback, producing a single pulse or pulse train is called a

blocking oscillator.

3.Which are the two important elements of a blocking oscillator?

1. Active element like transistor.

2. A pulse transformer.

4. What is pulse transformer?

A pulse transformer is basically a transformer which couples a source of pulses of electrical

energy to the load, keeping the shape and other properties of pulses unchanged. The voltage level

of the pulse can be raised or lowered by designing the proper turns ratio for the pulse

transformer.

5.What is an Oscillator?

An Oscillator is a Circuit, which generates an alternating voltage of any desired frequency. It

can generate an a.c output signal without requiring any externally applied input signal.

6.What is a beat frequency oscillator?

Beat frequency Oscillator (BFO) is an Oscillator in which a deserved signal frequency such as

the beat frequency produced by combining the different signal frequencies such as on different

radio frequencies.

7.What is sustained Oscillation?

The electrical oscillations in which amplitude does not change with time are called as

sustained oscillations. It is also called as Undamped Oscillation.

8.What is meant by resonant Circuit Oscillators?

LC Oscillators are known as resonant circuit oscillator because the frequency of operation of

LC Oscillator is nothing but a resonant frequency of tank circuit or LC tank circuit produces

sustained Oscillation at the resonant circuit oscillator.

9.What is delay time?

The time required for the current to rise to 10% of its maximum (saturation) value Ics is called

the delay time td.

10.What is the total turn on time?

The total turn on time is ton is the sum of the delay time and rise time, ton = td

+ tr

Where,td = Delay time. tr = Rise time.

11.What is storage time?

The interval that elapses between the transition of the input waveform and the time when the

collector current has dropped to 90 % of total output is called the storage time ts.


12.Define transition time.

The time interval during which the conduction transfer from one transistor to another transistor is

defined as transition time.

13.What is current time base generator?

The circuit which produces current which linearly increases with time is called current time base

generator.

14.What are the application of the blocking oscillator?

The blocking oscillator can be used as low impedance switch used to discharge a capacitor very

quickly. To produce large peak power pulses, both the types of oscillators cab be used. The

output of the blocking oscillator can be used to produce gating waveform with very low mark

space ratio. It may be used as frequency divider or counter in digital circuits.

15.List varies sweep circuits.

Exponential charging circuit Constant-current

charging circuit. Miller circuit

poot strap circuit Inductor circuit.

16.What do you mean by voltage time base generators?

Ciruits used to generate a linear variation of voltage with time are called voltage time base

generators.

17.What is the effect of ‘Q’ on stability?

Higher the value of Q,provides better selectivity, but smaller bandwidth and larger gain. Hence it

provides less stability.

18.What is meant by unloaded and loaded Q of tank circuit.

Unloaded Q is the ratio of stored energy to dissipated energy in a reactor or resonator.

The loaded Q (or) QL of a resonator is determined by how tightly the resonator is coupled to its

terminations.

19. What is the other name of astableBlocking Oscillator? 1. Diode controlled Astable Blocking Oscillator.

2. Re controlled Astable Blocking Oscillator. 20. How high duty cycle is obtained? 1. Using temperature compensated zener diode.

2.Using Ge diode in series with tertiary winding across the supply voltage


R110kΩ

R22.2kΩ R3

10kΩ

R4

1kΩC110nF

C3

120pF

Key=A50%

C2

100pF

Q1

2N3904

V112 V

3

00

1

0

0

C4

10nF

6 0

XSC1

A B

Ext Trig+

+

_

_ + _

0

T1

4

2

0

5

Ex.No: 09

TUNED COLLECTOR OSCILLATOR Date:

Aim:

To design the p-spice circuit for the given tuned collector oscillator circuit and simulate the waveforms.

Software Needed:

PSPICE Software

Circuit Diagram:

Procedure:

1) Open new PSPICE schematic design window.

2) Select the required components using place part tool.

3) Connect the components as per the circuit.

4) Connect the sources and output indicators in the nodes.

5) Save the design and Run the simulation.

6) Observe the waveforms.


Output:

Result:

Thus the P-Spice circuit for tuned oscillator circuit has been designed and output waveform is simulated.


Viva - Questions

1. What is an oscillator? An oscillator is a circuit which basically acts as a generator, generating the output

signal which oscillates with constant amplitude and constant desired frequency.

2. What is the difference between open loop and closed loop gain of the circuit?

S.NO Open loop gain Closed loop gain

The gain of the amplifier is ratio The ratio of the output to input,

of output to input when no considering the overall effect of the

1. feedback is used is called open feedback is called closed loop gain.

loop gain

3. State the Barkhausen criterion for an oscillator.

1. The total phase shift around a loop, as the signal proceeds from input through amplifier, feedback network back to input again, completing a loop, is precisely

00 or 360

0.

2. The magnitude of the product of the open loop gain of the amplifier (A) and the feedback factor β is unity. i.e., A β = 1. 4.

4. Explain the concept of positive feedback.

The feedback is a property which allows to feedback the part of the output, to the same circuit as its input. Such a feedback is said to be positive whenever the part tf the output that is fed back to the amplifier as its input, is in phase with the original input signal applied to the amplifier.


Every resistance has some free electrons. Under the influence of room temperature, these free electrons move randomly in various directions. In such a movement of the free electrons generate a voltage called noise voltage, across the resistance. Such noise voltage provides the starting voltage for the oscillator.

6. Why in practice A β is kept greater than unity.

To amplify small noise voltage present, so that oscillations can start, A β is kept initially greater than unity. 7.Give the over all classification of oscillators?

a. Waveform type (sinusoidal, square, triangular,etc.,) b. Circuit components (LC, RC,etc.,)

c. Range of frequency –A.F (audio), R.F (radio) d. Type of feedback (RC phase shift, Wein bridge are feedback used, UJT

relaxation oscillators uses no feedback)

8.What are the frequency sensitive arms?

The arms which decide the frequency of oscillations i.e., R1-C1 and R2-C2 are the frequency sensitive arms. 9. What is the gain requirement in the wein bridge oscillator?

The gain requirement for wein bridge oscillator is minimum 3.


10. How to obtain Hartley oscillator from the basic form of LC oscillator?

Using X1 and X2 as inductors and X3 as capacitor, Hartley oscillator from basic form of LC oscillator is obtained.

11. Name two high frequency Oscillators. v. Hartley Oscillator vi. Colpitts Oscillator vii. iii. Crystal Oscillator

12. What are the essential parts of an Oscillator?

Tank circuit (or) Oscillatory circuit.

Amplifier (Transistor amplifier) Feedback Circuit.

13.What is meant by tuned amplifiers? Tuned amplifiers are amplifiers that are designed to reject a certain range of frequencies

below a lower cut off frequency ωL and above a upper cut off frequency ωH and allows only a narrow band of frequencies.

14.Classify tuned amplifiers. 1.Single tuned amplifier. 2.Double tuned amplifier. 3.Synchronously tuned amplifier. 4.Stagger tuned amplifier.

15.What are the advantages of double tuned amplifier?

In double tuned amplifiers, the tuning is done both at the primary and secondary.The double tuned amplifiers provide a wider bandwidth, flatter pass band and a greater

selectivity.

16.What is the other name for tuned amplifier? Tuned amplifiers used for amplifying narrow band of frequencies hence it is also known as

“ narrow band amplifier” or “Band pass amplifier”.

17.Define resonance. The reactance of the capacitor equals that of the inductor reactance. i.e

ωC. = 1 / ωL.

18.What is Quality factor?

The ratio of inductive reactance of the coil at resonance to its resistance is known as quality factor.

Q = XL / R

19.Define gain bandwidth product of a tuned amplifier. The gain bandwidth(GBW) product is a figure of merit defined in terms of mid band

gain and upper 3-db frequency fh as GBW = | Aim fh | = gm / 2πc

20.What is the other name for tuned amplifier? Tuned amplifiers used for amplifying narrow band of frequencies hence it is also known as

“ narrow band amplifier” or “Band pass amplifier”.


R1

3kΩ

Key=A50%

R21kΩ

R310kΩ

R41kΩ

R510kΩ

C110nF

C210nF

2

4

Q1

BC107BP

Q2

BC107BP

R633kΩ

R710kΩ

R82.2kΩ

R92.2kΩ

R1068kΩ

R1110kΩ

R121kΩ

C3

10uF

C4

10uF

5

0

6

3

C5

100uF

11

10

V1

15 V 13

0

XSC1

A B

Ext Trig+

+

_

_ + _

8

0

7

Ex.No: 10

WEIN BRIDGE OSCILLATOR Date:

Aim:

To design the p-spice circuit for the given wein bridge oscillator and simulate the waveforms.

Software Needed:

PSPICE Software

Circuit Diagram:

Procedure:








Output:

Result:

Thus the P-Spice circuit for the given wein bridge oscillator has been designed and output waveform is

simulated.


Viva - Questions

1. What is the gain requirement in the wein bridge oscillator? The gain requirement for wein bridge oscillator is minimum 3.

2. How to obtain Hartley oscillator from the basic form of LC oscillator

Using X1 and X2 as inductors and X3 as capacitor, Hartley oscillator from basic form of LC oscillator is obtained.

3. What is amplifier?

Amplifier is a device which is used to amplification purpose.

4. What is amplification? A low strength signal is converted into strengthen signal ie) boost up process

5. List the disadvantages of Rc phase shift Oscillator.

It is ideal for frequency adjustment over a wide range.

It requires a high β transistor to overcome losses in the network.

6. What is the difference between amplifier and oscillator? Amplifier is working in the negative feedback while oscillator working in the positive feedback. 7. Write down the general applications of oscillators.

a) As a local oscillator in radio receivers. b) In T.V receivers.

c) In signal generators. d) As clock generation for logic circuits.

e) AM and FM transmitters. f) In phase lock loops.

8. What are the conditions for oscillation?

The total phase shift of an oscillator should be 360o.

For feedback oscillator it


9. What is an Oscillator? An Oscillator is a Circuit, which generates an alternating voltage of any desired

frequency. It can generate an a.c output signal without requiring any externally applied input signal. 10.What is a beat frequency oscillator?

Beat frequency Oscillator (BFO) is an Oscillator in which a deserved signal frequency such as the beat frequency produced by combining the different signal frequencies such as on different radio frequencies. 11.What is sustained Oscillation?

The electrical oscillations in which amplitude does not change with time are called as sustained oscillations. It is also called as Undamped Oscillation.

12.What is meant by resonant Circuit Oscillators?

LC Oscillators are known as resonant circuit oscillator because the frequency of operation of LC Oscillator is nothing but a resonant frequency of tank circuit or LC tank circuit produces sustained Oscillation at the resonant circuit oscillator.


13.What are the types of sinusoidal oscillator? Mention the different types of sinusoidal oscillator?

RC phase shift Oscillator.

Wein bridge Oscillator.

Hartley Oscillator Colpitts

Oscillator Crystal Oscillator 14.What is Barkhausan criterion?

The conditions for oscillator to produce oscillation is given by Barkhausan criterion. They are :

(i). The total phase shift produced by the circuit should be 360o or 0

o

(ii).The Magnitude of loop gain must be greater than or equal to 1 i.e. . A׀β1≤ ׀.

15.Name two high frequency Oscillators. e. Hartley Oscillator ii. Colpitts Oscillator

iii.Crystal Oscillator 16.What are the essential parts of an Oscillator?

f. Tank circuit (or) Oscillatory circuit.

g. Amplifier (Transistor amplifier) h. Feedback Circuit.

17.What is feedback amplifier? The part of the output is given to the input of the circuit called as feedback amplifier.

18.Classify the feedback amplifiers.

1) Voltage series feedback amplifier 2) Current series feedback amplifier

3) Voltage shunt feedback amplifier 4) Current shunt feedback amplifier

19.What is meant by neutralization?

It is the process by which feedback can be cancelled by introducing a current that is equal in magnitude but 180

o out of phase with the feedback signal at the input of the active device.

The two signals will cancel and the effect of feedback will be eliminated. This technique is termed as neutralization.

20.What is the application of tuned amplifiers? The application of tuned amplifiers to obtain a desired frequency and rejecting all other frequency in

(i). Radio and T .V broadcasting as tuning circuit. (ii). Wireless communication system.


Ex.No: 11

DOUBLE AND STAGGER TUNED AMPLIFIERS Date:

Aim:

To design the p-spice circuit for the given double tuned and stagger tuned amplifiers and simulate the

waveforms.

Software Needed:

PSPICE Software

Circuit Diagram:

(a) Double tuned amplifier

Procedure:







V1

12 V

R191kΩ

R310kΩ

R46.2kΩ R5

1kΩ

R624kΩ

R75.6kΩ

R84.7kΩ

R91.2kΩ

C1

2uFC210uF

C3

2uF

C410uF

Q1

BC107BP

Q2

BC107BP

45

2

8

0

0

R282kΩ

3

1C5

10uF

7

R10

47kΩ

6

XFG1

10

0

XSC1

A B

Ext Trig+

+

_

_ + _

9

0

11


Output:

(b) Stagger tuned amplifier

V1

12 V

R191kΩ

R310kΩ

R46.2kΩ R5

1kΩ

R624kΩ

R75.6kΩ

R84.7kΩ

R91.2kΩ

C1

2uFC210uF

C3

2uF

C410uF

Q1

BC107BP

Q2

BC107BP

45

2

8

0

0

R282kΩ

3

1C5

10uF

7

R10

47kΩ

6

XFG1

10

0

XSC1

A B

Ext Trig+

+

_

_ + _

V2

12 V R1524kΩ

R165.6kΩ

R174.7kΩ

R181.2kΩ

C910uF

Q4

BC107BP

C10

10uF

18

0

15

11

12

14

0

9


Output:

Result:

Thus the P-Spice circuit for the given double tuned and stagger tuned amplifiers has been designed and

output waveform are simulated.


Viva - Questions

1. What do you mean by tuned amplifiers? The amplifiers which amplify only selected range of frequencies (narrow band of

frequencies) with the help of tuned circuits (parallel LC circuit) are called tuned amplifiers. 2.What are the various types of tuned amplifiers?

Small signal tuned amplifiers Single tuned amplifiers

(i) Capacitive coupled (ii) Inductively coupled (or) Transformer coupled

Double tuned amplifiers Stagger tuned amplifiers

Large signal tuned amplifiers 3.Give the expressions for the resonance frequency and impedance of the tuned circuit.

f r = 1

& Z R = L

2π

CR

LC

4. What is the response of tuned amplifiers? The response of tuned amplifier is maximum at resonant frequency and it falls

sharply for frequencies below and above the resonant frequency. 5.When tuned circuit is like resistive, capacitive and inductive?

(1) At resonance, circuit is like resistive. (2) For frequencies above resonance, circuit is like capacitive. (3) For frequencies below resonance, circuit is like inductive.

6.What are the various components of coil losses?

(4) Copper loss (5) Eddy current loss (6) Hysteresis loss

7.Define Q factor of resonant circuit.

(7) It is the ratio of reactance to resistance. (8) It also can be defined as the measure of efficiency with which inductor can store the

energy.

Q=2п *(Maximum Energy Stored per cycle / Energy dissipated per cycle)

8.What is dissipation factor?

(9) It is defined as 1/Q. (10) It can be referred to as the total loss within a component.

9.Define unloaded and loaded Q of tuned circuit.

(11) The unloaded Q or QU is the ratio of stored energy to dissipated energy in a reactor or resonator.

(12) The loaded Q or QL of a resonator is determined by how tightly the resonator is coupled to its terminations.

10.Why quality factor is kept as high as possible in tuned circuits?

When Q is high, bandwidth is low and we get better selectivity. Hence Q is kept as high as possible in tuned circuits. When Q is high inductor losses are less.


11.List various types of cascaded Small signal tuned amplifiers.

2. Single tuned amplifiers.

3. Double tuned amplifiers. 4. Stagger tuned amplifiers.

12.How single tuned amplifiers are classified?

5. Capacitance coupled single tuned amplifier. 6. Transformer coupled or inductively coupled single tuned amplifier.

13.What are single tuned amplifiers? Single tuned amplifiers use one parallel resonant circuit as the load

impedance in each stage and all the tuned circuits are tuned to the same frequency. 14. What are double tuned amplifiers?

Double tuned amplifiers use two inductively coupled tuned circuits per stage, both the tuned circuits being tuned to the same frequency.

15. What are stagger tuned amplifiers? Stagger tuned amplifiers use a number of single tuned stages in cascade, the

successive tuned circuits being tuned to slightly different frequencies. 16.What is the effect of cascading single tuned amplifiers on bandwidth? Bandwidth reduces due to cascading single tuned amplifiers. 17.List the advantages and disadvantages of tuned amplifiers. Advantages:

3. They amplify defined frequencies.

4. Signal to Noise ratio at output is good. 5. They are well suited for radio transmitters and receivers.

18.What are the advantages of double tuned amplifier over single tuned amplifier?

1. It provides larger 3 dB bandwidth than the single tuned amplifier and hence provides the larger gain-bandwidth product.

2. It provides gain versus frequency curve having steeper sides and flatter top.

19.What the advantages are of stagger tuned amplifier? The advantage of stagger tuned amplifier is to have better flat, wideband

characteristics.

20. Define gain bandwidth product of a tuned amplifier.

A gain band width product of a tuned amplifier is defined as product of 3 db band width

and gain at response of the tuned amplifier.


Ex.No: 12

BISTABLE MULTIVIBRATOR Date:

Aim:

To design the bi-stable multivibrator circuit and simulate the waveforms using P-Spice.

Software Needed:

PSPICE Software

Circuit Diagram:

Procedure:







Q1

BC107BP

Q2

BC107BP

R13kΩ

R2220kΩ

R3100kΩ

R4

47kΩ

R5

47kΩ

R63kΩ

R7220kΩR8

100kΩ

C1

1nF

C2

1nF

D11N4007GP

D21N4007GP

4

6

2

8

V1

5 V 9

0

0

XSC1

A B

Ext Trig+

+

_

_ + _

50

XSC2

A B

Ext Trig+

+

_

_ + _

1

0

V2

-1 V 1 V

0.5msec 1msec

7


Output:

Q1 Output

Q2 Output

Result:

Thus the P-Spice circuit for the bi-stable circuit has been designed and output waveform are simulated.


Viva - Questions

1.Which circuits are called multivibrators? The electronic circuits which are used to generate nonsinusoidal waveforms are called multivibrators. They are two stage switching circuits in which the output of the first stage is fed to the input of the second stage and vice-versa.

2.What are the various types of multivibrators?

Astable multivibrator Bistable multivibrator Monostable multivibrator

3. What is astable multivibrator?

A multivibrator which generates square wave without any external triggering pulse is called astable multivibrator.


4.List the applications of Astable multivibrator? Used as square wave generator It is used in the construction of digital voltmeter and SMPS. It can be operated as an oscillator over a wide range of audio and radio

frequencies. 5.State the basic action of monostable multivibrator.

It has only one stable state. The other state is unstable referred as quasi-stable state. It is also known as one-shot multivibrator or univibrator.

6. Mention the applications of one short multivibrator? It is used to function as an adjustable pulse width generator. It is used to generate uniform width pulses from a variable width pulse train.

It is used to generate clean and sharp pulses from the distorted pulses. It is used as a time delay unit since it produces a transition at a fixed time after the trigger signal.

7.Which multivibrator would function as a time delay unit? Why? Monostable multivibrator would function as a time delay unit since it produces a transition at a fixed time after the trigger signal.

8.What is Bistable multivibrator? The Bistable multivibrator has two stable states. The multivibrator can exist indefinitely in either of the two stable states. It requires an external trigger pulse to change from one stable state to another. The circuit remains in one stable state unless an external trigger pulse is applied.


It is used as memory elements in shift registers, counters, and so on. It is used to generate square waves of symmetrical shape by sending regular triggering pulse to the input. By adjusting the frequency of the trigger pulse, the width of the square wave can be altered.


10.What are the two methods of triggering for bistable multivibrators?


Symmetrical triggering 11.How many stable states do bistable Multivibrator have?

Two stable states.


When an external trigger pulse is applied, the circuit changes from one stable state to another.

13.What are the different names of bistable Multivibrator?

Eccles Jordan circuit, trigger circuit, scale-of-2 toggle circuit, flip-flop and binary.

14. What are the other names of monostable Multivibrator? One-shot, Single-shot, a single-cycle, a single swing, a single step Multivibrator, Univibrator.

15.Why is monostable Multivibrator called gating circuit? The circuit is used to generate the rectangular waveform and hence can be used to gate other Circuits hence called gating circuit.

16.What are the main characteristics of Astable Multivibrator? The Astable Multivibrator automatically makes the successive transitions from one quasi- stable State to other without any external triggering pulse.

17.What is the other name of Astable Multivibrator- why is it called so? As it does not require any external pulse for transition, it is called free running Multivibrator.

18.What are the two types of transistor bistable Multivibrator?

Fixed bias transistor circuit Self bias transistor circuit.

19.Why does one of the transistor start conducting ahead of other?

The characteristic of both the transistors are never identical hence after giving supplies one of the Transistors start conducting ahead of the other.

20.What are the two stable states of bistable Multivibrator? . Q1 OFF (cut off) and Q2 ON (Saturation)

Q2 OFF (Cut off) and Q1 On (Saturation)


R1500Ω

R2

1kΩ

R3300Ω

R4100Ω

R5500Ω

Q1

2N2222A

Q2

2N2222A

V35 V

23

7

0

XFG1

XSC1

A B

Ext Trig+

+

_

_ + _

6

0

1

0

4

Ex.No: 13

SCHMITT TRIGGER WITH PREDICTABLE HYSTERESIS Date:

Aim:

To design the p-spice circuit for Schmitt trigger with predictable hysteresis and simulate the waveforms.

Software Needed:

PSPICE Software

Circuit Diagram:

Procedure:








Output:

Result:

Thus the P-Spice circuit for the Schmitt trigger with predictable hysteresis has been designed and output

waveform is simulated.


Viva - Questions

1.What is Schmitt trigger? It is a wave shaping circuit, used for generation of a square wave from a sine wave input. It is a bistable circuit in which two transistor switches are connected generatively.

2. What is UTP of the Schmitt Trigger? The level of Vi at which Q1 becomes ON and Q2 OFF is called Upper Threshold Point.

3. What is the other name for UTP? It is also called input turn on threshold level.

4. What is LTP of the Schmitt trigger? The level of Vi at which Q1 becomes OFF and Q2 on is called Lower Threshold Point.

5. Define transfer Characteristics of Schmitt trigger. The graph of output voltage against input voltage is called transfer characteristics of Schmitt trigger.

6.What is the important application of Schmitt trigger?

It is used as an amplitude comparator It is used as a squaring circuit.

7.What is meant by Hysteresis voltage in a Schmitt trigger? The difference between UTP (Upper Threshold Point) and LTP (Lower Threshold Point) is called Hysteresis voltage (VH). It is also known as Dead Zone of the Schmitt trigger.

8.List the applications of Schmitt trigger. It is used for wave shaping circuits. It can be used for generation of rectangular waveforms with sharp edges from a sine wave or any other waveform.

It can be used as a voltage comparator.

9.How a Schmitt trigger is different from a multivibrator? A Schmitt trigger has an input and an output; the output is a squared-up version of the input. As long as the input is constant, the output of the Schmitt trigger is also constant. A multivibrator typically has no inputs (other than power), only an output: an oscillating signal.

10.What is delay time? The time required for the current to rise to 10% of its maximum (saturation) value Ics is

called the delay time td.

11.What is the total turn on time? The total turn on time is ton is the sum of the delay time and rise time, ton =

td + tr Where,

td = Delay time. tr = Rise time.


12.What is storage time? The interval that elapses between the transition of the input waveform and the time when

the collector current has dropped to 90 % of total output is called the storage time ts. 13.Define transition time.

The time interval during which the conduction transfer from one transistor to another transistor is defined as transition time.

14.What is Leading edge response? At start there is an overshoot and then the pulse settles down. The response till it settles down

after the overshoot is called leading edge response.

15.What is trailing edge response? The response generally extends below the zero amplitude after the end of pulse width is

called back swing. The portion of response from backswing till it settles down is trailing edge response.

16.What is flat top response? The portion of the response between the trailing edge and the leading edge is called flat top

response.

17.Define rise time of a pulse. The rise time is an important parameter related to this part of the response. It is defined by the

time required by the pulse to rise from 10 % of its amplitude to 90 % of its amplitude.

18.What is Turn-off time (tOFF) in transistor?

The sum of the storage time (ts) and the fall time (tf) is called the turn-OFF

time (tOFF).

(tOFF) = (ts) + (tf)

19.What is comparator? The nonlinear circuit which was used to perform the operation of clipping may also be used to perform the operation of comparison is called the comparator.

The comparator circuit compares an input signal with a reference voltage.

20.What are the other names of speed up capacitors? Commutating Capacitors

Transpose capacitors


Ex.No: 14

MONOSTABLE MULTIVIBRATOR Date:

Aim:

To design the p-spice circuit for the monostable multivibrator and simulate the waveforms.

Software Needed:

PSPICE Software

Circuit Diagram:

Procedure:







Q1

BC107BP

Q2

BC107BP

R110kΩ

R310kΩ

R5

10kΩ

R610kΩ

V1

5 V XSC1

A B

Ext Trig+

+

_

_ + _

0

0

0

00

6

R2120kΩ

7

C2

10uF

3

4

D21N4148

2

C1

100nF

1V2

-1 V 1 V

0.2msec 1msec

5

0


Output:

Result:

Thus the P-Spice circuit for monostable multivibrator has been designed and output waveform is

simulated.


Viva - Questions

1. Which circuits are called multivibrators? The electronic circuits which are used to generate nonsinusoidal waveforms are called multivibrators. They are two stage switching circuits in which the output of the first stage is fed to the input of the second stage and vice-versa.

2.What are the various types of multivibrators?

Astable multivibrator Bistable multivibrator Monostable multivibrator

3. What is astable multivibrator?

A multivibrator which generates square wave without any external triggering pulse is called astable multivibrator.


4.List the applications of Astable multivibrator? Used as square wave generator It is used in the construction of digital voltmeter and SMPS. It can be operated as an oscillator over a wide range of audio and radio

frequencies. 5.State the basic action of monostable multivibrator.

It has only one stable state. The other state is unstable referred as quasi-stable state. It is also known as one-shot multivibrator or univibrator.

6. Mention the applications of one short multivibrator? It is used to function as an adjustable pulse width generator. It is used to generate uniform width pulses from a variable width pulse It is used to generate clean and sharp pulses from the distorted pulses. It is used as a time delay unit since it produces a transition at a fixed time after the trigger signal.

7.Which multivibrator would function as a time delay unit? Why? Monostable multivibrator would function as a time delay unit since it produces a transition at a fixed time after the trigger signal.

8.What is Bistable multivibrator? The Bistable multivibrator has two stable states. The multivibrator can exist indefinitely in either of the two stable states. It requires an external trigger pulse to change from one stable state to another. The circuit remains in one stable state unless an external trigger pulse is applied.


It is used as memory elements in shift registers, counters, and so on. It is used to generate square waves of symmetrical shape by sending regular triggering pulse to the input. By adjusting the frequency of the trigger pulse, the width of the square wave can be altered.


10.What are the two methods of triggering for bistable multivibrators?


Symmetrical triggering 11.How many stable states do bistable Multivibrator have?

Two stable states.


When an external trigger pulse is applied, the circuit changes from one stable state to another.

13.What are the different names of bistable Multivibrator?

Eccles Jordan circuit, trigger circuit, scale-of-2 toggle circuit, flip-flop and binary.

14. What are the other names of monostable Multivibrator? One-shot, Single-shot, a single-cycle, a single swing, a single step Multivibrator, Univibrator.

15.Why is monostable Multivibrator called gating circuit? The circuit is used to generate the rectangular waveform and hence can be used to gate other Circuits hence called gating circuit.

16.What are the main characteristics of Astable Multivibrator? The Astable Multivibrator automatically makes the successive transitions from one quasi- stable State to other without any external triggering pulse.

17.What is the other name of Astable Multivibrator- why is it called so? As it does not require any external pulse for transition, it is called free running Multivibrator.

18.What are the two types of transistor bistable Multivibrator?

Fixed bias transistor circuit Self bias transistor circuit.

19.Why does one of the transistor start conducting ahead of other?

The characteristic of both the transistors are never identical hence after giving supplies one of the Transistors start conducting ahead of the other.

20.What are the two stable states of bistable Multivibrator? . Q1 OFF (cut off) and Q2 ON (Saturation)

Q2 OFF (Cut off) and Q1 On (Saturation)


D1

1N4148

D21N4148

D31N4148

Q1

2N2222A0

R120kΩ

R21kΩ

R31MΩC1

100nF

0

0

5

0

XSC1

A B

Ext Trig+

+

_

_ + _

0

Q4

2N3906

Q5

2N3906

2

3

6

4

V112 V

1

0

Ex.No: 15

VOLTAGE & CURRENT TIME BASE GENERATOR Date:

Aim:

To design the p-spice circuit for the voltage and current time base generator and simulate the

waveforms.

Software Needed:

PSPICE Software

Circuit Diagram:

Procedure:








Output:

Result:

Thus the P-Spice circuit for voltage and current time base generator has been designed and output

waveform is simulated.


Viva - Questions

1.Define overshoot. It is the amount by which the output exceeds its amplitude during first attempt.

2. What is leading edge response? At start there is an overshoot and then pulse settles down. The response till it settles

down after the overshoot is called leading edge response. 3. What is trailing edge response?

The response generally extends below the zero amplitude after the end of pulse width is called back swing. The portion of response from back swing till it settles down is called trailing edge response. 4. Define flat top response.

The portion of the response between the trailing edge and the leading edge is called flat top response. 5. Define droop or a tilt.

The displacement of the pulse amplitude during its flat response is called droop or a tilt. 6.What are the applications of pulse transformer? Pulse transformer can be used to

1. Change the amplitude and impedance level of a pulse.

2. Invert the polarity of the pulse. 3. Produce a pulse in a circuit having negligible d.c. resistance. 4. Differentiate a pulse.

7.When does the core saturate? When L->o as B-> Bm, the core saturates.

8. What is the other name of astable Blocking (Oscillator? Free running blocking Oscillator.

9.What are the two types of astable Blocking Oscillator? 3. Diode controlled Astable Blocking Oscillator.

4. Re controlled Astable Blocking Oscillator. 10.Define Sweep time in saw tooth generator.

The period during which voltage increases linearly is called sweep time.

11.What is the other name of saw tooth generator? Ramp generator. 12.Define Displacement error in the saw tooth generator?

It is defined as the maximum differences between the actual sweep voltage and linear sweep which passes through the beginning and end points of the actual sweep. 13. What is constant current charging?

A capacitor is charged with a constant current source. 14. What is the miller circuit?

Integrator is used to convert a step waveform into ramp waveform.

15.Mention the various methods of controlling the pulse. 1. Use of common base configuration.

2. Use of common collector configuration. 3. Use of core saturation method.

4. Use of shorted delay line.


16.What is mark space ratio? The ratio of time for which Q is On to time for which Q is OFF is called mark-space

ratio. If this is unity, then the output is almost symmetrical square wave.

17. Define Duty cycle.

The duty cycle is defined as the ratio of the ON time tp to the time period T. Mathematically it is given by, D= tp/T

18.How high duty cycle is obtained?

1. Using temperature compensated zener diode. 2. Using Ge diode in series with tertiary winding across the supply voltage.

19.What do you mean by voltage time base generators?

Circuits used to generate a linear variation of voltage with time are called Voltage time-base generators. 20. What do you mean by linear time base generators?

Circuits provide an output waveform which exhibits a linear variation of voltage with time are called linear time base generators.


CONTENT BEYOND THE SYLLABUS (USING VIRTUAL LAB)

Ex.No.1

SCHMITT TRIGGER USING OP-AMP Date:

AIM

(i)To study the operation of Op-Amp based Schmitt trigger circuit and observe the input and

output waveforms of Schmitt trigger. (ii)To measure the upper and lower threshold points and compare with their calculated values.

APPARATUS REQUIED

LABview Softt ware

THEORY

Schmitt trigger is essentially a multi-vibrator having two stable states. The output remains in

one of the stable states inde nitely. The transition from one stable state to the other takes place

when the input signal changes appropriately (triggers appropriately). Bistable operation needs an

ampli er with a regenerative (positive) feedback with loop gain greater than unity. The circuit is

often used to convert square waves with slowly varying edges to sharp edges required in digital

circuits. It is also used for debouncing the switches.

The circuit shown in Fig. 1 is that of an inverting Schmitt trigger. The circuit has two stable state outputs. The output will either be at +VSAT or VSAT . The circuit uses a potential divider formed by R1 and R2 to provide a positive DC feedback. The circuit is essentially a comparator with positive DC feedback. The voltage at VA is compared with the input signal. The voltage VA can take either of the two values.


Refer the transfer characteristic in Fig. 2 for understanding how the output changes with the input signal. When the input signal VIN > VT H the output switches to VSAT and remains at this level till VIN < VT L when the output switches to +VSAT . The values at which the output makes transition from one level to the other are called Threshold points or trip points. The input voltage at which the output makes transition from +VSAT to VSAT is VT H and the input voltage at which the output makes transition from +VSAT to VSAT is de ned

PROCEDURE

1.Run the experiment by pressing “RUN” button.

2.Choose “Schmitt trigger” from menu list.

3.Press “START” to perform the Schmitt trigger experiment.

4.After performing STEP 3, Schmitt trigger experiment will be displayed.


5. Use cursors to measure value of VTH and VTL from waveform graph.

Result

Thus the operation of Op-Amp based Schmitt trigger circuit is observed the input and

output waveforms of Schmitt trigger is drawn.


Ex.No.2

ASTABLE MULTIVIBRATOR USING OP-AMP Date:

AIM

To study the operation of Op-Amp based actable multivibrator circuit and observe the input

and output waveforms. (ii)To measure the upper and lower threshold points and compare with their calculated values.

APPARATUS REQUIED

LABview Softt ware

THEORY

An astable multivibrator switches between two states with a frequency determined by an RC

time constant. This feature may be used to make a square wave generator. When the circuit is

turned ON, the OPAMP's output saturates to either positive or negative rail. Assuming that the

OPAMP saturates at the positive rail (+VSAT ), the capacitorstarts charging through the resistor R,

and the voltage across the capacitor starts to rise exponentially towards +VSAT . As soon as the

voltage at the OPAMP's inverting terminal tries to cross that at the non-inverting terminal (the

OPAMP's output voltage fed back by the potential divider formed byR1 and R2), the output

switches over to the opposite rail VSAT as shown in Fig. 2 and the capacitor starts to discharge

through R exponentially. Once the inverting terminal reaches the voltage of the non-inverting

terminal, the output again drives to the opposing rail voltage and the cycle begins again.

Thus, the astable multivibrator creates a square wave with no input signal.


Figure 2: Output waveform and VC of Astable Multivibrator


PROCEDURE

1.Run the experiment by pressing “RUN” button.

2.Choose “Astable multivibrator” from menu list.

3.Press “START” to perform the Schmitt trigger experiment.

4.After performing STEP 3, Astable multivibrator experiment will be displayed.

5. Observe the input and output waveforms.

Circuit Diagram & Input, Output:


Result

Thus the operation of Op-Amp based Astable multivibrator circuit is observed the input

and output waveforms.


dr.n.g.p.institute of technology coimbatore 48

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