Question

Draw the circuit diagram of differential instrumentation amplifier and derive the expression of its output. Precisely control of temperature in many industries is critical to ensure the quality of the product. Discuss how you will use the instrumentation amplifier using transducer bridge to measure the temperature. Use block diagram to illustrate your concept.

Answer 1

In order to measure and control some of physical quantity such as temperature, humidity, water flow etc. transducer is used to drive display unit which indicate change in the above parameters. The signal level of transducer is low which doesn’t drive display unit. Hence in order to raise signal level of transducer Instrumentation amplifier is used.

Important features of an instrumentation amplifier are as follows:

1. High CMRR (Common Mode Rejection Ratio)
2. Large input impedance.
3. Low output impedance.
4. High gain accuracy.
5. Both the input voltage should not be same i.e V1 ≠ V2 .
6. High gain stability with low temperature coefficient.

Derivation of output voltage equation :

Consider Figure 1 ,