What is Voltage Follower using Op-Amp? Circuit Diagram, Derivation & Working

The circuit in which output voltage is exactly equal and in-phase with its input, then the circuit is known as voltage follower.

A non-inverting amplifier, whose gain is equal to 1, acts as a voltage follower. The circuit includes an op-amp and a wire connecting the output and input terminals. A non- inverting amplifier configured as voltage follower is illustrated in figure below.

Figure 1: Voltage Follower.

In the above figure, since the complete output is feedback to the inverting input. the gain of the circuit becomes. The output voltage of a non-inverting amplifier is given by,

\[{{V}_{out}}=\left( 1+\frac{{{R}_{F}}}{{{R}_{1}}} \right){{V}_{in}}\]

Since R_F = 0, R₁ = ∞, we get

\[{{V}_{out}}={{V}_{in}}\]

Features of Voltage Follower

1. The input impedance is high i.e., in the order of MΩ. Hence, it draws negligible current from signal source.
2. Due to its low output impedance, it can be used as buffer for connecting high impedance source to a low impedance load.
3. Voltage follower has large bandwidth.
4. The voltage follower circuit output follows the input precisely with zero phase shift.
5. It has unity gain.

Applications of Voltage Follower

In instrumentation amplifier, loading effect of transducer is eliminated by using voltage follower between transducer and amplifier.