LIC & AC Lab Manual
CBCS Scheme
15ECL48
Instrumentation Amplifier Aim: To design instrumentation amplifier for a differential mode gain of ‘Av’ using three amplifiers.
Components Required: Sl No 1
3
Components Op-amp AFO and Power Supply CRO
4
Resistors
5 6 7 8 9
Capacitors DRB Breadboard CRO probes Connecting Wires
2
Specification µA741
Quantity 1
-
1 each
300 Ω, 3.9 kΩ, 10 kΩ, 220 kΩ, 47 kΩ 0.01 µF -
1 1, 2, 2, 1, 1 2 1 1 3 1 Set
Theory: Circuit Diagram:
Figure 1: Instrumentation Amplifier
Dept ECE, GMIT, Davangere
Page 1
LIC & AC Lab Manual
CBCS Scheme
15ECL48
Circuit Design: Consider Voltage Gain of instrumentation amplifier as 900 and input signal amplitude as 15 mV. Assume Voltage Gain of Instrumentation Amplifier is,
Current flowing through resistor R1 is,
Resistor R1 is given as,
Differential voltage gain of stage 1 is,
Resistor R2 is given as,
Dept ECE, GMIT, Davangere
Page 2
LIC & AC Lab Manual
CBCS Scheme
15ECL48
Output voltage Vo is given as,
Current through resistor R4 is,
Resistor R4 is given as,
Resistor R3 is given as,
Resistor R5 is given as,
Dept ECE, GMIT, Davangere
Page 3
LIC & AC Lab Manual
CBCS Scheme
15ECL48
Input and Output Waveform:
Figure 2: Instrumentation Amplifier Input and Output Waveform
Dept ECE, GMIT, Davangere
Page 4
LIC & AC Lab Manual
CBCS Scheme
15ECL48
Tabulation: Input Voltage Vi = Vd = V1 – V2 = 15 mV
f (Hz)
Vo (V)
Procedure:
Circuit elements are determined as per the design criteria.
Circuit is rigged up as shown in figure 1.
Input voltage for differential amplifiers V1 = 25 mV and V2 = 10 mV are set on the frequency generator.
Power supply is switched on and the DRB is tuned to get output waveform for the desired gain in the pass-band and is observed on the CRO.
Input frequency is varied from 100 Hz to 50 kHz.
Each step corresponding output is measured and noted down.
The gain in dB is calculated by using the formula Af = 20 log vo/vi
The graph of gain v/s frequency is plotted on the graph sheet. Dept ECE, GMIT, Davangere
Page 5
LIC & AC Lab Manual
CBCS Scheme
Amplitude and time period of the waveform is tabulated.
Trace the waveform on tracing sheet.
15ECL48
Result: An instrumentation amplifier having a differential mode gain of ‘Av’ using three amplifiers has been designed and verified.
Dept ECE, GMIT, Davangere
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