experiment 9: non-linear applications of...

EXPERIMENT 9:

Non-Linear Applications of Op-Amp

4.5 Analyzing Symmetric Square Wave Generator Constructed By 555 Ic

4.6 Analyzing Pulse Width Modulation Mode (Asymmetric) Square Wave Generator

Constructed By Op-Amp

4.7 Analyzing Asymmetric Square Wave Generator Constructed By 555 Ic

4.8 Analyzing Triangular, Sinusoidal And Square Wave Generator Constructed By Xr

2206 Ic

EXPERIMENT MODULE Y-0014 / 04

EXPERIMENT: 4.5

ANALYZING SYMMETRIC SQUARE WAVE GENERATOR CONSTRUCTED BY 555 IC

PREPARATION INFORMATION:

The 555 is an oscillator and timer integrated circuit that is widely used today. Some properties

of 555 IC are;

Being able to operate as stable, astable and monostable multivibrator ,

Being able to operate as adjustable oscillator,

Timing capacity from micro seconds to hours,

Giving outputs compatible to TTL,

Being able to output current up to 200mA

Operating at voltages between 5V and 15V.

Figure 5.1

The pin diagram of the 555 IC is shown in figure 5.1. The output signal of the 555 IC is a

square wave. The symmetric square wave generator constructed by 555 IC is given in figure 5.2.

Figure 5.2

As it is seen in the figure 5.2, just a few peripheral elements are used in the symmetric square

wave generator constructed by 555 IC.

The period of the square wave is; T= 0,693(R1+2RT) C.

The frequency is calculated by; f= CRTRt )21(

44,11

EXPERIMENT 4.5: EXPERIMENTAL PROCEDURE:

Connect the circuit as shown in the figure.

1- Apply power to the circuit. Set the potentiometer to its maximum resistance position

(middle pin is up). Measure the amplitude and the frequency of the signal on the oscilloscope screen.

2- Vary the position of the potentiometer slowly. At which frequency the output waveform is

deformed.

3- Set the potentiometer to its minimum resistance position (middle pin is down). Measure the

frequency for that case.

4- Calculate the minimum and maximum frequencies mathematically. Compare with the

experimental results.

EXPERIMENT: 4.6

ANALYZING PULSE WIDTH MODULATION MODE (ASYMMETRIC) SQUARE WAVE

GENERATOR CONSTRUCTED BY OPERATIONAL AMPLIFIER


In some cases asymmetric (different negative and positive signal durations) square waves may

be desired. Circuits with high currents can be controlled by setting the positive time duration to zero or

a small value compared to negative time duration.

Figure 6.1

The asymmetric square wave generator constructed by operational amplifier is shown in figure

6.1. The operational amplifier operates as a comparator. The output signal is positive if the voltage at

the non-inverting input is greater than the voltage at the inverting input. During that time, the capacitor

“C” connected to the inverting input charges up through the diodes D1-D2 and potentiometers P1 and

P2. When the charge voltage exceeds the voltage at the non-inverting input, the output signal changes

and turns out to be negative. That situation continues until the capacitor is discharged so that the

voltage at the inverting input is lower than the voltage at the non-inverting input.

If the voltage at the non-inverting input remains greater than the voltage at the inverting input,

the output voltage remains positive. That is the initial condition. That process repeats itself. A square

wave is obtained at the output.

The width of the negative voltage is controlled by the diode D1 and potentiometer P1 in the

negative feedback network. The width of the positive voltage is controlled by the diode D2 and

potentiometer P2. Different charge and discharge times are obtained by varying the potentiometers P1

and P2. So the desired asymmetric square wave is obtained at the output. If both of the potentiometers

are set to their middle position, a symmetric square wave is obtained at the output.

EXPERIMENT 4.6: EXPERIMENTAL PROCEDURE

Connect the circuit as shown in the figure.

1- Apply power to the circuit. Measure the amplitude of the output signal. Why is that value

obtained?

2- Set the potentiometers P1 and P2 to their middle positions. Define the output waveform.

3- Set the potentiometer P1 to zero (middle pin is down). What happened to the output signal?

Why?

4- Set the potentiometer P1 to middle position. At that time set the potentiometer P2 to zero

(middle pin is down). What happened to the output signal? Why?

5- Set the potentiometers to maximum (middle pin is up) position one by one. Define the

output waveform.

EXPERIMENT: 4.7

ANALYZING ASYMMETRIC SQUARE WAVE GENERATOR CONSTRUCTED BY 555 IC


Figure 7.1

The asymmetric square wave generator made up of 555 IC is seen in Figure 7.1. The number of

circuit elements is small as the 555 IC is programmed as square wave generator and timer. The output

current of the 555 IC is too big as 200mA. Many relays and lamps used in electronics can directly be

controlled by using 555 IC.

Figure 7.2

The output is seen in Figure 7.2 when the potentiometer is so adjusted that the mid-point is

above (A point) and below (B point). There is current on the load in small time intervals when the

mid-point of the potentiometer is at point A as seen in Figure 7.2A. The time length of the current that

flows through the load is maximum when the mid-point of the potentiometer is at point B as seen in

Figure 7.2B.

A DC motor or a lamp can ideally be controlled with a circuit like that.


Make the circuit connections as in the figure.

1- Set the potentiometer to the mid-value. Apply power to the circuit. Define the output signal.

Measure the amplitude of the output signal?

2- If we connect a lamp to the output pins and set the mid-point of the potentiometer to above

point, how does the lamp emit light?

3- If we connect a lamp to the output pins and set the mid-point of the potentiometer to below

point, how does the lamp emit light?

EXPERIMENT: 4.8

ANALYZING TRIANGULAR, SINE AND SQUARE WAVE GENERATOR CONSTRUCTED

BY XR2206 IC


The XR2206 IC the circuit designed as a voltage controlled oscillator (VCO) that can generate

triangular, sine and square waves. They can operate under 10V-26V supply voltage. The output

amplitude changes directly proportional with the supply voltage. They operate stable under 0.001Hz

and 1MHz frequency band.

Figure 8.1

The pin specifications of the XR2206 IC are seen in Figure 8.1 and its usage as sine, triangular

and square wave generator is seen in Figure 8.2. As seen, the number of circuit elements is small. The

R1+R4 resistors and C2 capacitor determine the frequency band and the C2 capacitor is used more

than once. A generator having gradual frequency output is obtained if C2 is used with a commutator.

The frequency of the output signal;

F=1/(R1+R4).C1.

Figure 8.2


Make the circuit connections as in the figure.

1- Set the oscilloscope to AC. Set the sine/triangular select pin to sine state (switch pin is

down). At this moment, the switch is closed. Apply the power to the circuit. Define the waveform in

the oscilloscope?

2- Adjust the P1, P2 and P3 potentiometers at any frequency value. Obtain a distortion free

sine wave in the oscilloscope. Measure the peak to peak voltage value (Vpp) of the sine wave?

3- This time, set the sine/triangular select pin to triangular state (switch pin is up). This time

the switch becomes open. Adjust the P1 and P3 potentiometer. Obtain a distortion free triangular wave

in the oscilloscope. Determine the peak to peak voltage value (Vpp) of the triangular wave?

4- Set the oscilloscope to DC. Connect the positive terminal of the oscilloscope to the square

wave output socket as seen in the figure below. Define the shape in the figure?

5- Determine the amplitude of the square wave?

6- Set the P4 potentiometer to minimum and maximum. Measure the frequency band of the

circuit?

experiment 9: non-linear applications of...

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