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Electronic Circuits (DKT214) 2013/2014
Laboratory Module
UNIVERSITI MALAYSIA PERLIS
DKT 214 – ELECTRONIC CIRCUITS
EXPERIMENT 2 (B)
Common Op-Amp Circuits
Name: __________________________________
Matric No.: ______________________________
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Date : _______________
Electronic Circuits (DKT214) 2013/2014
Laboratory Module
EXPERIMENT 2 (B)
Common Op-Amp Circuits
ACKNOWLEDGEMENT
Most of the materials presented in the lab module are taken from laboratory module EMT212
and the book Experiments in Electronic Devices and Circuits (Bogart & Brown, Sixth Edition,
Prentice Hall Publishing, 2004) with minor amendments.
1.
OBJECTIVE:
1.1 To demonstrate the use of operational amplifier for performing
differentiation and integration.
2.
INTRODUCTION:
2.1
Differentiator
A differentiator is a circuit that performs a calculus operation called differentiation. It
produces an output voltage proportional to the instantaneous rate of change of the
input voltage. Common applications of a differentiator are to detect leading and
trailing edges of a rectangular pulse or to produce a rectangular output from a ramp
input.
input
output
Figure 2.1: Waveform of differentiator
As shown in Figure 2.1, the output an electronic differentiator is proportional to the
rate of change of the input waveform at any point in time. To perform differentiation, a
capacitor is connected in series with the input as shown in Figure 2.2. The equation
(2.1) can be used to determine the output voltage of the op-amp differentiator.
vo (t )   RC
dvin (t )
(2.1)
dt
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Figure 2.2: Ideal Differentiator
Figure 2.3: Practical Op-amp differentiator
The ideal differentiator is inherently unstable in practice due to the presence of some
high frequency noise in every electronic system. An ideal differentiator would amplify
this small noise. For instance, if vnoise = Asin(t) is differentiated, the output would
be vout = Acos(t). Even if A = 1V, when  = 210MHz) vout would have an
amplitude of 63V! To circumvent this problem, it is traditional to include a series
resistor at the input and a parallel capacitor across the feedback resistor as shown in
Figure 2.3, converting the differentiator to an integrator at high frequencies for
filtering.
2.2
Integrator
An integrator is a circuit that performs a mathematical operation called integration.
The most popular application of an integrator is in producing a ramp of output
voltage, which is linearly increasing or decreasing voltage. The integrator is
sometimes called the Miller integrator, after the inventor.
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input
output
Figure 2.4: Waveform of integrator
As shown in Figure 2.4, the output an electronic integrator is proportional to the total
area under the input waveform up to that point in time. To perform integration, a
capacitor is connected in the feedback path of the amplifier as shown in Figure 2.5.
However, any dc voltage appearing at the input of an integrator will cause the output
voltage to rise (or fall) until it reaches its maximum possible value. To prevent this
undesirable occurrence, a resistor RF , is connected in parallel with the feedback
capacitor as illustrated in Figure 2.6. Any dc input voltage, such as the input offset
voltage of the amplifier, is then simply amplified by the dc gain, RF/R1.
Figure 2.5: Ideal Integrator
Figure 2.6: Practical Op-amp integrator
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The equation (2.2) can be used to determine the output voltage of the operational
amplifier integrator.
vo (t )
3.
1 t

vin (t ) dt  vo (0)
RC 0
(2.2)
COMPONENT AND EQUIPMENT:
3.1 Resistors:
470 k
47 k
10 kΩ
470 Ω
3.2 Capacitors:
0.22 uF
0.001 uF
3.3 LM 741 OP-AMP
3.4 DC Power Supply
3.5 Oscilloscope
3.6 Function Generator
3.7 Breadboard
3.8 Digital multimeter
4.
PROCEDURE:
4.1
Op-amp Integrator
4.1.1
To investigate the use of an operational amplifier to perform
mathematical integration, connect the following circuit.
Figure 4.1 Integrator circuit
4.1.2
With Vs adjusted to produce a 10 Vpp sine wave at 20 Hz and using a
dual-trace oscilloscope set to ac input coupling, measure and record
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peak value of the output voltage Vo in TABLE 1. Repeat this procedure
for the remaining frequencies in TABLE 1. Sketch the output voltage
waveform with respect to the input voltage for frequency at 1 kHz in
GRAPH 1.
4.1.3
4.2
Set Vs to a ±10 Vpp square wave at 100 Hz. Using a dual-trace
oscilloscope, sketch the output voltage with respect to the input
voltage in GRAPH 2. Record also the output voltage.
Op-amp Differentiator
4.2.1
Figure 4.2 shows an op-amp differentiator circuit. Construct a circuit
on the breadboard. Apply 500 Hz, 10Vpp sine wave input signal.
Measure and record peak value of the output voltage Vo in TABLE 2.
Repeat this procedure for the remaining frequencies in TABLE 2.
Sketch the output voltage waveform for frequency at 100 Hz in
GRAPH 3.
Figure 4.2 Differentiator circuit
4.2.2
Set Vs to a ±2 Vpp square wave at 200 Hz. Using a dual-trace
oscilloscope, sketch the output voltage with respect to the input
voltage in GRAPH 4. Record the output voltage.
4.2.3
Now apply a 1 kHz, 2Vpp triangular wave input signal to the circuit.
Sketch the output voltage in GRAPH 5. Record the output voltage.
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RESULT:
TABLE 1
Frequency
vo(volts)
20 Hz
50 Hz
100 Hz
500 Hz
1 kHz
TABLE 2
Frequency
vo(volts)
500 Hz
200 Hz
100 Hz
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6.
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QUESTIONS:
6.1 State the function of differentiator.
6.2 State the function of integrator.
6.3 Did the results of procedure step 4.1.3 verify an integrator's response to a
square wave input? Explain briefly.
6.4 Did the results of procedure step 4.2.3 verify a differentiator's response to
a triangular wave input? Explain briefly.
6.5 What is the differenct between practical differentiator and ideal
differentiator?
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CONCLUSION:
Based on your measurement data and graph, make an overall conclusion of
differentiator and integrator op-amp.
Differentiator is….
Integrator is….
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Additional Notes:
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