Electronic Circuit Labs
OPAMP Basic application circuits
Lab 5 – OPAMP Basic application circuits
Aims:
[1] To introduce the operational amplifier or OPAMP, an important building block
used in many electronic circuits.
[2] To understand the characteristics of operational amplifiers and their uses in
simple configurations.
[3] To calculate and measure the input and output signals of simple OPAMP
configurations.
1. Background
1.1 Introduction
- The operational amplifier (OPAMP) could be considered a voltage controlled
voltage source with very high gain.
- There are five ports as shown in figure 1.1
Fig. 1.1
- Positive and negative power supply ports are usually not shown in an OPAMP
circuit scheme, but keep in mind that, in reality, they must be connected to suitable
power supplies in order to keep the OPAMP operates properly.
- In this experiment, we assume that the OPAMP is ideal, that means:
In = Ip = 0: No current into the input terminals
Ri → : Infinite input resistance
Ro → 0: Zero output resistance
A → : Infinite open loop gain.
1.2 Basic OPAMP configurations
Inverting amplifier:
The basic inverting amplifier configuration is shown on Fig 1.2a. The input signal, Vin,
is applied to the inverting terminal.
Fig. 1.2a
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OPAMP Basic application circuits
The voltage gain of the ideal inverting amplifier is: Av 
Rf
Vo
 .
Vin
Ri
Non-inverting amplifier:
Fig 1.2b shows the basic non-inverting amplifier configuration. The negative
feedback is maintained and the input signal is now applied to the non-inverting terminal.
Fig. 1.2b
The voltage gain of the ideal non-inverting amplifier is: Av 
Rf
Vo
 1 .
Vin
Ri
Summing amplifier:
Fig 1.2c shows a basic summing amplifier with two input signals.
Fig. 1.2c
V
V 
The output voltage is: Vout  Rf  in 1  in2  .
 Ri 1 Ri 2 
The Integrator:
The integrator circuit in Fig 1.2d is constructed by using a feedback capacitor
instead of a resistor in the inverting amplifier.
Fig. 1.2d
The input-output relation is:
t
dV
Vin
1
 C out  Vout (t)    Vin ( )d  Vout (0)
R
dt
RC 0
The Differentiator:
A fundamental differentiator circuit constructed with a capacitor and a resistor is
shown of Fig 1.2e.
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OPAMP Basic application circuits
Fig. 1.2e
The input-output relation is:
Vout (t)  RC
dVin
dt
2. Experiment preparation
- Review the Operational Amplifiers theories: Microelectronic Circuits 6th Edition,
Sedra/Smith, pages 53-108.
- Read the Experiment procedure carefully.
- Write the experiment preparation, including:

Principle schemes of all experiment circuits.

Formulas and calculated results (if available).

Method for measuring circuit parameters.

Photo all the tables in lab manual (in order to record or draw the results
immediately while doing the experiments).
3. Materials
- Main kit: ELECTRONIC LAB ANA-MAIN
- Module: OPAMP Basic application circuits
- Oscilloscope: GRS-6052A
- Multimeter: Fluke 45
- Connectors
4. Experiment procedure
Connect the power supplies for the module as shown on Fig 4.0. Keep these
connections in the rest of Lab 7 so that the OPAMP can operate properly.
4.1 Inverting Amplifier
a. Construct the circuit on Fig 1.2a using module OPAMP Basic application circuits as
shown on Fig 4.1 (Ri = R4 = 1k, Rf = R11 = 100k). The input frequency is set to 1kHz (sin
wave), the magnitude is adjusted so that the magnitude of the output is 8Vp-p. Use the
oscilloscope (in AC mode) to watch Vin, Vo, plot Vin, Vo in Table 4.1.
b. Redo previous steps when R11 is replaced by R10 (10k) and R9 (1k).
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Fig. 4.0
Fig. 4.1a
Table 4.1 - Inverting amplifier
CH1: DC mode - input
50 mV
VOLTS/DIV:………….
Ri = R4
Rf = R11
86 mV
Vip-p:………………….
CH2: DC mode - ouput
2V
VOLTS/DIV:………….
8.08 V
Vop-p:…………………
180 (degree)
Phase (Vi vs Vo):……..
93.95
Av:…………………….
200 us
TIME/DIV:…………….
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OPAMP Basic application circuits
CH1: DC mode - input
200 mV
VOLTS/DIV:………….
784 mV
Vip-p:………………….
CH2: DC mode - ouput
2V
VOLTS/DIV:………….
Ri = R4
Rf = R10
8.00 V
Vop-p:…………………
180 (degree)
Phase (Vi vs Vo):……..
10.31
Av:…………………….
200 us
TIME/DIV:…………….
CH1: DC mode - input
2V
VOLTS/DIV:………….
7.76 V
Vip-p:………………….
CH2: DC mode - ouput
2V
VOLTS/DIV:………….
Ri = R4
Rf = R9
8.00 V
Vop-p:…………………
180 (degree)
Phase (Vi vs Vo):……..
1.031
Av:…………………….
200 us
TIME/DIV:…………….
4.2 Non-inverting amplifier
Fig. 4.2
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OPAMP Basic application circuits
a. Construct the circuit on Fig 1.2b using module OPAMP Basic application circuits as
shown on Fig 4.2 (Ri = R4 = 1k, Rf = R11 = 100k). The input frequency is set to 1kHz (sin
wave), the magnitude is adjusted so that the magnitude of the output is 8Vp-p. Use the
oscilloscope (in AC mode) to watch Vin, Vo, plot Vin, Vo in Table 4.2.
b. Redo previous steps when R11 is replaced by R10 (10k) and R9 (1k).
Table 4.2- Non-inverting amplifier
CH1: DC mode - input
50 mV
VOLTS/DIV:………….
Ri = R4
Rf = R11
82 mV
Vip-p:………………….
CH2: DC mode - ouput
2V
VOLTS/DIV:………….
8.08 V
Vop-p:…………………
0 (degree)
Phase (Vi vs Vo):……..
98.54
Av:…………………….
200 us
TIME/DIV:…………….
CH1: DC mode - input
200 mV
VOLTS/DIV:………….
Ri = R4
Rf = R10
720 mV
Vip-p:………………….
CH2: DC mode - ouput
5V
VOLTS/DIV:………….
8.00 V
Vop-p:…………………
0 (degree)
Phase (Vi vs Vo):……..
11.1
Av:…………………….
200 us
TIME/DIV:…………….
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OPAMP Basic application circuits
CH1: DC mode - input
1V
VOLTS/DIV:………….
3.96 V
Vip-p:………………….
CH2: DC mode - ouput
5V
VOLTS/DIV:………….
Ri = R4
Rf = R9
8.00 V
Vop-p:…………………
0 (degree)
Phase (Vi vs Vo):……..
2.02
Av:…………………….
200 us
TIME/DIV:…………….
4.3. Summing amplifier
a. Construct the circuit on Fig 1.2c using module OPAMP Basic application circuits as
shown on Fig 4.3 (Vin1 = VDC-adjustable, Ri1 = R3 = 4.7k, Vin2 = +5VDC, Ri2 = R4 = 1k, Rf = R9
= 1k). Use the FLUKE45 multimeter (in VDC mode) to measure Vo, then fill in Table 4.3a.
Fig. 4.3
Table 4.3a - Summing Amplifier - DC inputs
Vin1
Vo
-15V
-1.829
-10V
-2.889
-5V
-3.863
+5V
-6.042
+10V
-7.095
+15V
-8.151
b. Vin1 is fixed to +5VDC, Vin2 is now connected to sin-wave, 1kHz, 4Vp-p, use the
oscilloscope (in DC mode) to watch Vin2 and Vo, then plot these signals in Table 4.3b.
c. Vin1 is now fixed to -3VDC, Vin2 keep unchanged (sin-wave, 1kHz, 4Vp-p), use the
oscilloscope (in DC mode) to watch Vin2 and Vo, then plot these signals in Table 4.3b.
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Table 4.3b - Summing amplifier - DC and AC inputs
CH1: DC mode - input
1V
VOLTS/DIV:………….
4.00 V
Vip-p:………………….
CH2: DC mode - output
2V
VOLTS/DIV:………….
Vin1 = +5VDC
Vin2 =
sin-wave,
1kHz, 4Vp-p
4.16 V
Vop-p:…………………
500 us
TIME/DIV:…………….
CH1: DC mode - input
1V
VOLTS/DIV:………….
4.00 V
Vip-p:………………….
CH2: DC mode - ouput
2V
VOLTS/DIV:………….
Vin1 = -3VDC
Vin2 =
sin-wave,
1kHz, 4Vp-p
4.40 V
Vop-p:…………………
500 us
TIME/DIV:…………….
Fig. 4.4
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OPAMP Basic application circuits
4.4. The integrator
Construct the circuit on Fig 1.2d using module OPAMP Basic application circuits as
shown on Fig 4.4 (C = C1 = 10nF, R = R4 = 1k  ). The function generator is switched to
square wave, the frequency is 1kHz, the magnitude is 4Vp-p. Use the oscilloscope (in AC
mode) to watch Vin and Vo, plot these signals in Table 4.4.
Table 4.4 - The integrator
CH1: AC mode - input
1V
VOLTS/DIV:………….
Vin =
Square
wave,
1kHz, 4Vp-p
4.08 V
Vip-p:………………….
CH2: AC mode - output
5V
VOLTS/DIV:………….
9.60 V
Vop-p:…………………
500 us
TIME/DIV:…………….
4.5. The differentiator
Construct the circuit on Fig 1.2e using module OPAMP Basic application circuits as
shown on Fig 4.5 (C = C1 = 10nF, R = R9 = R6 = 1k). The function generator is switched to
triangle wave, the frequency is 1kHz, the magnitude is 4Vp-p. Use the oscilloscope (in AC
mode) to watch Vin and Vo, plot these signals in Table 4.5.
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Table 4.5 - The Differentiator
CH1: AC mode - input
1V
VOLTS/DIV:………….
Vin =
Triangle
wave,
1kHz, 4Vp-p
4.04 V
Vip-p:………………….
CH2: AC mode - output
1V
VOLTS/DIV:………….
1.96 V
Vop-p:…………………
500 us
TIME/DIV:…………….
5. Further questions for the experiment report
- Analysis and compare experiment results with calculated results.
- When a sin wave Asin(t) is connected to the input of a integrator (instead of the
square wave in the experiment), write the formula for Vo, sketch Vin and Vo.
- When a sin wave Asin(t) is connected to the input of a differentiator (instead of
the triangle wave in the experiment), write the formula for Vo, sketch Vin and Vo.
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