Write a short note on instrumentation amplifier.

Q.) Write a short note on instrumentation amplifier.

 Subject: electronic devices and circuits

Instrumentation Amplifier

An instrumentation amplifier (IA) is a type of differential amplifier that is designed to amplify the difference between two input signals while rejecting common-mode noise. This makes it ideal for applications where the desired signal is small and the noise level is high.

Principle of Operation

The basic principle of operation of an IA is to use three operational amplifiers (op-amps) in a feedback configuration. The first op-amp is used as a differential amplifier, which amplifies the difference between the two input signals. The second op-amp is used as a subtractor, which subtracts the output of the differential amplifier from a reference voltage. The third op-amp is used as a non-inverting amplifier, which amplifies the output of the subtractor.

The overall gain of the IA is determined by the ratio of the feedback resistor (Rf) to the input resistors (Rin). The common-mode rejection ratio (CMRR) of the IA is determined by the matching of the input resistors.

Advantages of Instrumentation Amplifiers

  • High gain: IAs can provide very high gains, typically in the range of 100 to 10,000.
  • High CMRR: IAs have very high CMRRs, typically in the range of 80 to 120 dB.
  • Low noise: IAs have very low noise levels, typically in the range of 1 to 10 nV/√Hz.
  • Wide bandwidth: IAs have wide bandwidths, typically in the range of 100 kHz to 1 MHz.

Applications of Instrumentation Amplifiers

IAs are used in a wide variety of applications, including:

  • Biomedical measurements: IAs are used to amplify bioelectric signals, such as electrocardiograms (ECGs), electroencephalograms (EEGs), and electromyograms (EMGs).
  • Industrial measurements: IAs are used to amplify sensor signals, such as temperature, pressure, and flow.
  • Audio amplifiers: IAs are used to amplify audio signals in high-end audio systems.
  • Communication systems: IAs are used to amplify signals in communication systems, such as telephone and cable television systems.

Conclusion

Instrumentation amplifiers are versatile and widely used devices that are ideal for amplifying small signals in the presence of noise. Their high gain, high CMRR, low noise, and wide bandwidth make them ideal for a wide variety of applications.