Voltage Follower

A circuit in which the output voltage follows the input voltage is called voltage follower circuit.

voltage_follower

The node B is at potential Vin . Now node A is also at the same potential as B i.e. Vin.

VV= Vin

Now node A is directly connected to the output. Hence we can write,

Vo = V=  Vin

  • It can be seen that output voltage follows the input hence the circuit is called voltage follower circuit. It is also called source follower, unity gain amplifier, buffer amplifier or isolation amplifier.

 

  • Advantages of Voltage follower :
  1. Very large input impedance, of the order of M Ω.
  2. Low output impedance, almost negligible. Hence it can be used to connect high impedance source to a low impedance load, as a buffer.
  3. It has large bandwidth.
  4. The output follows the input exactly without a phase shift.

 

The input resistance of the buffer is extremely large, it draws negligible current from the signal source. Therefore the signal source is not loaded.

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