ab-17 common base analog lab experiment … lab experiment board ver. 1.0 an iso 9001: 2000 company...

AB-17COMMON BASE

AMPLIFIER

ANALOG LAB

EXPERIMENT BOARD

Ver. 1.0

An ISO 9001: 2000 company

94-101, Electronic Complex, Pardesipura INDORE-452010, India.

AB-17

Tel.: 91-731-2570301 Fax: 91-731-2555643Email: [email protected] Web: www.scientech.bz

Scientech Technologies Pvt. Ltd. 2

http://www.scientech.bz/

mailto:[email protected]

AB-17

COMMON BASE AMPLIFIERAB-17

TABLE OF CONTENTS

1.Introduction 3

2. Theory 5

3.Experiment 11

To study the Common Base Amplifier (NPN)and to evaluate –Operating Point of the Common Base AmplifierVoltage gain, Current gain of the Amplifier AV, AiInput and Output impedance of Amplifier.

4.Datasheet 13

5.Warranty 15

6.List of Service Centers 16

7.List of Accessories with AB-17 16


AB-17

INTRODUCTION

AB-17 is a compact, ready to use COMMON BASE AMPLIFIER experiment board. This is useful for students to understand the functionality of common base amplifier and to study various operational parameters of an transistor Amplifier. It can be used as stand alone unit with external DC power supply or can be used with SCIENTECH ANALOG LAB ST-2612 which has built in DC power supply, AC power supply, function generator, modulation generator, continuity tester, toggle switches, potentiometer.

List of Boards :

Model Name

AB-01AB-02AB-03AB-04AB-05AB-06AB-07AB-08AB-09AB-15AB-16AB-18AB-19AB-21AB-22AB-23AB-26

AB-28AB-29AB-30AB-31AB-32 AB-33 AB-41AB-42

AB-43

Diode characteristics (Si, Zener, LED)Transistor characteristics (CB NPN)Transistor characteristics (CB PNP)Transistor characteristics (CE NPN)Transistor characteristics (CE PNP)Transistor characteristics (CC NPN)Transistor characteristics (CC PNP)FET characteristicsRectifier CircuitsCommon Emitter AmplifierCommon Collector AmplifierRC-Coupled AmplifierCascode AmplifierClass A AmplifierClass B Amplifier (push pull emitter follower)Class C Tuned AmplifierPhase Locked Loop (FM Demodulator & Frequency Divider/Multiplier)Multivibrators (Astable / Monostable)F-V and V-F ConverterV-I and I-V ConverterZener Voltage Regulator Transistor Series Voltage RegulatorTransistor Shunt Voltage RegulatorDifferential Amplifier (Transistorized)Operational Amplifier (Inverting / Non-inverting / Differentiator)Operational Amplifier (Adder/Scalar)


AB-17

AB-44

AB-45AB-51AB-52AB-53AB-56AB-65

AB-66

AB-67

AB-81

AB-82

AB-83

AB-84

AB-90AB-91AB-92AB-93

Operational Amplifier (Integrator/ Differentiator)Schmitt Trigger and ComparatorActive filters (Low Pass and High Pass)Active Band Pass Filter Notch Filter Fiber Optic Analog LinkPhase Shift OscillatorWien Bridge OscillatorsColpitt OscillatorKirchoff’s Laws (Kirchoff’s Current Law & Kirchoff’s Voltage Law)Thevenin’s and Maximum power Transfer TheoremReciprocity and Superposition TheoremTellegen’s TheoremTwo port network parameterOptical Transducer (Photovoltaic cell)Optical Transducer (Photoconductive cell/LDR)Optical Transducer (PhotoTransistor)

…and many more


AB-17

THEORY

Amplification is the process of increasing the strength of signal. An Amplifier is a device that provides amplification (the increase in current, voltage or power of signal) without appreciably altering the original signal.

Bipolar transistors are frequently used as an amplifiers. Transistor can be used as an Amplifier in three configurations:

1. Common Base

2. Common Emitter

3. Common Collector

Common Base Configuration :

In this arrangement, the input signal is applied between emitter and base and the output is taken from the collector to base shown in Fig 1. In this arrangement input current is emitter current and output current is collector current.

Current relations in CB configurations

IE = IC + IB

IC = α / (1- α ) IE + 1 / (1-α ) ICBO

α = IC / IE

Where IC = Collector current

IE = Emitter current

ICBO = current through collector to base when emitter is open.

α = Common Base DC current gain. α ranges between .9 - .99.

Fig. 1


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Transistor as an Amplifier in CB configuration :

The conditions for which transistor works as an amplifier are:

1. Emitter base junction is always forward biased.

2. Collector - Base junction is always reverse biased.

To achieve this, a DC voltage VEE is applied in the input circuit in addition to signal shown in Fig 1. this voltage is known as bias voltage and it's magnitude is such that it always keep the input circuit forward biased regardless the polarity of signal.

A input circuit has low resistance, therefore a small change in signal voltage causes a appreciable change in emitter current, this causes almost same change in collector current due to transistor action. The collector current is flowing through high load resistance Rc produces a large voltage across it, thus a weak signal applied in the input circuit appears in the amplified form in collector circuit.

Operation of Common Base Amplifier :

In order to get faithful amplification, the transistor is properly DC biased. The purpose of DC biasing is to obtain a certain DC collector current(Ic) at a certain DC collector voltage(VCB). These values of current and voltage are called operating point (Quiescent point). To obtain DC operating point some biasing methods are used called biasing circuits. These biasing arrangements should be such as to operate the transistor in Active region.

The Most commonly used Biasing circuits is voltage divider method. In this method two resistances R1. and R2 are connected across the supply voltage VCC and provide proper biasing. A voltage divider formed by R1 and R2. The voltage drop across R2 forward biased the base emitter junction which causes the base current to flow. Thus, collector current flows even in zero signal condition. Resistance RE provides stabilization.

V2 = VCC * R2 / (R1 + R2)V2 = VBE + VE

V2 = VBE + IERE

IE = (V2 - VBE) / RE

IE is approx. equal to IC.IC = (V2 - VBE) / RE

VCE = VCC - IC (RC + RE)


AB-17

Fig. 2

This method is widely used because operating point of transistor can be made almost independent of beta (β) and provides good stabilization of operating point.

If this circuit is used to amplify AC voltages, some more components must be added to it.

Coupling Capacitors (CC): They are used to pass AC input signal and block the DC voltage from the preceding circuit. This prevents DC in the circuitory on the left of coupling capacitor from affecting the bias on transistor. The coupling capacitor also blocks the bias of transistor from reaching the input signal source. It is also called blocking capacitor.

Bypass Capacitors(CE): It bypasses all the AC current from the emitter to the ground. If the capacitor CE is not put in the circuit, the AC voltage developed across RE will affect the input AC voltage, such a feedback is reduced by putting the capacitor CE.

Rc: It represents the load resistance is connected at the output.

In this amplifier input signal is injected in to base-emitter circuit and output signal is taken out from the base-collector circuit.

When positive Half cycle of the signal is applied then,

1. Forward biased is decreased, since Vbe is negative w.r.t. collector ie. ground.

2. Base current is decreased.

3. Emitter current is decreased, similarly collector current is also decreased


AB-17

4. Drop across IcRc is decreased,

5. Hence Vcb is increased, consequently positive half-cycle of the output is obtained. i.e. input and output are in phase with each other.

Fig. 3

Fig 3 Input and Output Waveforms of Common Base Amplifier with load resistance 1KΩ

Operating Parameter of Common Base Amplifier

Voltage Gain :

It is the ratio of output voltage (Vout) obtained to input voltage (Vin).

AV = VOut / Vin


AB-17

Fig 4

Input Impedance :

It is the ratio of Input votage (Vin) to Input Current (Ii).

Zin = Vin / Ii

To measure the input impedance a known resistor (Rs) is placed in series before the input coupling capacitor and the impedance could be calculated using the equation.

Zin = Rs / (Av/Av`-l)

Where Av = voltage gain without the resistor (Rs)Av`= voltage gain with the resistor (Rs)

Output Impedance :

It is the ratio of Output voltage (Vout) to Output Current (Io).

Zout = Vout /Io

To measure the Output impedance a known resistor (Rs) is placed from output to ground and the output impedance could be calculated using the equation

Zout = (Av / Av`-l) * Rs

Where Av = voltage gain without the resistor (Rs)Av’ = voltage gain with the resistor (Rs)

Current gain : It is the ratio of Output current (Io) to Input current (Ii).

Ai = Io / Ii

The Current gain could be calculated using the equation

Ai = - Av * Zin / RL


AB-17

Characteristics of Common Base Amplifier :

1. It produces no phase reversal of input signal i.e., input and output signals are in phase with each other.

2. It has high voltage gain.

3. It has moderately low input impedance.

4. It has large output impedance.

5. It has current gain (β) less than one.

Comparisons of Amplifiers Configurations :

Characteristic

Type of Amplifier Circuit

Common Base

CommonEmitter

CommonCollector

Phase reversal No Yes No

Voltage Gain High Highest Nearly Unity

Input Impedance Lowest Moderate Highest

OuputImpedance Highest Moderate Lowest

Current Gain Nearly unity High (β) Highest (β + 1 )


AB-17

EXPERIMENT

Object :

To study the Common Base Amplifier and to evaluate –

Operating Point, Voltage gain (AV), Input impedance, and output impedance Current gain (Ai) of amplifier.

Apparatus Required :

1. Analog board of AB-17.

2. DC power supplies +12V external source or ST -2612 Analog Lab.

3. Digital Multimeter

4. 2 mm patch cords.

Circuit Diagram :

Circuit used to study Common Base Amplifier is shown in Fig 5.

Fig. 5


AB-17

Procedure :

1. Connect Testpoint 2 and Testpoint 3, Testpoint 4 and Testpoint 5, Testpoint 6 and Testpoint 7, using 2mm patch cords.

2. Connect +12V DC power supply at their indicated position from external source or ST -2612 Analog Lab.

3. Switch ON the power supply.

4. For the measurement of Quiescent Point measure the VCB by connecting Voltmeter between Testpoint 4 and Testpoint 6 Measure Collector current (Ic) by connecting Ammeter between Testpoint 4 and Testpoint 7.

5. Connect a sinusoidal signal of 10mV(p-p) at 25KHz frequency at the Testpoint 1 (Input of amplifier) from external source or ST-2612 Analog Lab.

6. Observe the amplified output on oscilloscope by connecting Testpoint 8 (output of amplifier) to oscilloscope.

7. Calculate Voltage gain of amplifier. Connect Load resistor of 1K ohms at the output and find the voltage gain of amplifier with load resistor.

8. Calculate input impedance, output impedance, and current gain of amplifier using the mentioned formulas with resistance 1K.

Result :

Operating Point of the Common Base amplifier

IC = ______________mA

VCB =______________V

Voltage gain of the amplifier AV =________________

Input impedance of amplifier Zin =________________

Output Impedance of amplifier Zout =________________

Current gain of amplifier Ai =________________


AB-17

DATASHEET


AB-17


AB-17

WARRANTY

1) We guarantee the instrument against all manufacturing defects during 24 months from the date of sale by us or through our dealers.

2) The guarantee covers manufacturing defects in respect of indigenous components and material limited to the warranty extended to us by the original manufacturer, and defect will be rectified as far as lies within our control.

3) The guarantee will become INVALID.a) If the instrument is not operated as per instruction given in the

instruction manual. b) If the agreed payment terms and other conditions of sale are not

followed.c) If the customer resells the instrument to another party.d) Provided no attempt have been made to service and modify the

instrument.4) The non-working of the instrument is to be communicated to us

immediately giving full details of the complaints and defects noticed specifically mentioning the type and sr. no. of the instrument, date of purchase etc.

5) The repair work will be carried out, provided the instrument is dispatched securely packed and insured with the railways. To and fro charges will be to the account of the customer.

DESPATCH PROCEDURE FOR SERVICEShould it become necessary to send back the instrument to factory please observe the following procedure:1) Before dispatching the instrument please write to us giving fully details

of the fault noticed.2) After receipt of your letter our repairs dept. will advise you whether it

is necessary to send the instrument back to us for repairs or the adjustment is possible in your premises.

Dispatch the instrument (only on the receipt of our advice) securely packed in original packing duly insured and freight paid along with accessories and a copy of the details noticed to us at our factory address.


AB-17

LIST OF SERVICE CENTERS

1. Scientech Technologies P. Ltd.90, Electronic Complex Ph: (0731) 5202959Pardesipura, Email: [email protected] INDORE – 452010

2. Scientech Technologies P. Ltd.First Floor, Ph.: (011) 26513912, 2686494314, Uday Park, Fax: (011) 26864943.NEW DELHI – 110049 Email: [email protected]

3. Scientech Technologies P. Ltd.New no.2, Old no.10, 4th street Ph.: (044) 52187548, 52187549

Venkateswara nagar, Adyar Fax: (044) 52187549CHENNAI – 600025 Email: [email protected]

4. Scientech Technologies P. Ltd. 202/19, 4th main street Ph.: (080) 51285011 Ganganagar, Fax: (080) 51285022 BANGALORE- 560032 Email: [email protected]

5. Scientech Technologies P. Ltd. First floor, L block Ph.: (022) 56299547 Ranjit studio compound, Fax: (022) 24155984 Dada Saheb Phalke road, Email: [email protected] Dadar (East) MUMBAI – 400014

6. Scientech Technologies P. Ltd. 988, Sadashiv Peth, Ph.: (020) 24461673 Gyan Prabodhini Lane, Fax: (020) 24482403 PUNE – 411030 Email: [email protected]

LIST OF ACCESSORIES

1. 2mm Patch cord (red) .........................................................1 Nos.

2. 2mm Patch cord (black) ......................................................3 Nos.

3. 2mm Patch cord (blue) ........................................................5 Nos.





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