Experiment # 08
Operational Amplifier Circuit II:
Measurements
Object:
The objectives of these experiment is to illustrate the use of linear amplfiers to perform basic operations
such as: addition, subtraction, integration, and differentiation.
Apparatus:
 DC power supply (O-20V)
 Oscilloscope
 Function generator
 Circuit board
 Operational amplifier
 Assorted resistors
 Assorted capacitors
Experimental set-up and procedure:
The operational amplifier (op amp) is an integrated circuit that contains several microscopic electronic
elements. The op amp that we are going to use in these experiments is called A 741. Its eight leads are
identified as follows:
Ofset N1
IN IN+
V-
1
2
3
4
8
7
6
5
NC
V+
Vout
Offset
Fig. 1
In all the following experiments we will use V+=+15V and V-= -15V.
Part I
1. Basic op. amp. Circuit adder
The following circuit gives the addition of two voltages V1 and V2 :
R0
V1
V2
R1
VVout
R2
V+
Fig.2
EGR 2402 Laboratory Manual
39
R
Vout = - ( 0
R1
Where
V1 +
R0
R2
V2
(1)
a) General characteristics :
1. Set-up this circuit (Fig. 2) using resistors in the range 10 to 100 KOhm
2. Use a sinusoidal source for V1 with low frequency ( f= 200 Hz) and small amplitude (v= 1 V)
3. Set V 2= 0 and select the resistors R0 and R1 so that Vout = -3V1
4. Record these values of R0 and R1
5. Determine the value of Vout where saturation occurs
6. Vary the input frequency and simultaneously measure Vout and Vin
7. Determine the amplification A given by :
Vout
A = Vin
8. Record your values in Table I :
f(KHz)
Vin
Vout
A
0.2
0.5
1.0
5.0
10.0
20
50
100
500
9. Plot A as a function of logf and discuss the result
10. Is the op.amp operating in its linear regime? Explain
b) Addition operation:
1. Set R1 = R2 and Equation (1) becomes:
Vout = R0 ( V1 + V2)
(2)
R1
2. Use a sinusoidal input for V1
3. Use a DC input for V2
4. Measure Vout for different values of V1 and V2 and record your results in Table II
V1
V2
V1+V2
2
1
4
1.5
6
3
8
4
10
6
Vout
5. Plot Vout versus (V1 + V2) and determine the addition gain (or slope) Aad:
6. Compare Aad to the value obtained from Equation (2) and give the % error
EGR 2402 Laboratory Manual
40
II. Basic circuit for difference:
The following circuit can be used to differentiate two input voltage V1 and V2
R0
V-
R1
V1
Vout
V2
R2
R0
fig.3
The output voltage is given by:
Vout =
R0
R1 ( V 2 – V 1 )
1. Set up the circuit in Fig. 3
2. Use a sinusoidal input for V1 and a DC input, for V2
3. Measure Vout for different values of V1 and V2 and record your results, in Table III :
V1 (VAC)
V2 (VDC)
2
1
4
1.5
6
3
8
4
10
6
V2 - V1
Vout
4. Plot Vout versus (V2 -V1) and determine the differential gain (or slope) Ad
5. Compare Ad to the value obtained from Equation (3) and give the % error
Part II
III. Basic circuit for integration
The following circuit is used to perform the integral of an input function:
R0
C
V1
V-
R1
Vout
The output voltage is given by :
Vout = -
V+
fig.4
1  Vin dt
RC
EGR 2402 Laboratory Manual
41
a) Square wave input:
1. Set up the circuit in Fig. 4 and use Vin as a square wave (2V amplitude)
2. What is the integral function of a square wave?
3. Choose R, R0, and C so that Vout corresponds to the integral form of Vin
4. Observe Vin and Vout simultaneously on the oscilloscope
5. Record these values of R, R0, and C
6. Plot the observed forms of Vin and Vout on the same graph
7. Compare Vout to Vin and explain what you observed
b) Sinusoïdal input:
1.Use a sine wave as input (2V amplitude)
2.What should be the output? Explain
3.Verifing this by using the oscilloscope and explain how you did it?
4. Give a sketch plot of Vin and Vout on the same graph
5. Change the frequency f of Vin and observe Vout
6.Does the frequency of Vout changes? Explain why
7. How does the amplitude of Vout changes with respect to f? Explain why ?
IV. Basic circuit for differentiation
The following circuit can be used to differentiate an input function:
R
R1
V-
Vin
Vout
Fig.5
The output signal is given by :
Vout = - RC
V+
dVin
dt
a) Triangular wave input:
1. Set up the circuit in Fig. 5
2. Use a triangular wave for Vin with an amplitude of about 2V
3. What is the derivative of a triangular function? Explain
4. Choose R so that Vout corresponds to the derivative form of Vin and record this value of Rand C
5. Observe both Vin and Vout on the oscilloscope
6. Plot the observed forms of Vin and V out on the same graph
7. Compare Vin and Vout and check Equation (5). Explain
b) Sinusoidal input:
1. Use a sine wave as input
2. What is the form of Vout?
3. Plot the form of Vin and Vout on the same graph
4. Change the frequency of Vin and observe Vout
5. Does the amplitude of Vout changes with f? If so, explain how and why ?
EGR 2402 Laboratory Manual
42
Conclusions:
1. Summarize briefly what you have learned in these experiments
2. From what you have learned, explain how would you proceed to perform the operation: 2 -1 = 1
(Draw the circuit)
EGR 2402 Laboratory Manual
43
Experiment # 08
Name:
Section:
Operational Amplifier Circuit I:
Measurements
1. Basic Op.Amp.Circuit adder
a) General characteristics:
4. The values of R0 and R1
5. The value of Vout where saturation occurs:
F(KHz)
Vin
Vout
A
V2 (VDC)
V1 + V2
Vout
V1 - V2
Vout
0.2
0.5
1.0
5.0
10
20
50
100
500
b) Addition operation:
V1 (VAC)
2
1
4
1.5
6
3
8
4
10
6
II Basic circuit for difference
V1 (VAC)
V2 (VDC)
2
1
4
1.5
6
3
8
4
10
6
II. Basic circuit for integration
a) Square wave input:
EGR 2402 Laboratory Manual
44
5. The values of R, R0, and C:
6. Plot the observed forms of Vin and Vout (on the same graph):
b Sinusoidal input :
4. Plot the observed forms of Vin and Vout (on the same graph)
IV. Basic circuit for differentiator:
a) Triangular wave input:
4. The values of R and C
6. Plot the observed forms of Vin and Vout (on the same graph)
b) Sinusoidal input:
3. Plot the observed forms of Vin and Vout (on the same graph):
EGR 2402 Laboratory Manual
45