Op amp as a Voltage follower
Voltage follower is a negative feedback op-amp amplifier circuit. It acts like emitter follower configuration of transistor based amplifiers. They provide unity gain to the applied input signals. Unity gain means the output voltage will be exactly equal in magnitude with the input voltage.
In the above figure a non-inverting voltage follower is shown. The input voltage V1 is applied on the non-inverting pin of the op-amp. Here the feedback resistance Rf is zero i.e. short circuit. The gain of the amplifier reduces from ideally infinity to unity.
If V1 is the input voltage at the inverting pin and V0 is the output voltage of the op-amp, then V0 is exactly equal to V1 in magnitude. Hence the gain is given by the following equation.
Voltage follower is generally used for amplify the current of a signal keeping the voltage same incase of driving high output loads (low resistance circuits).
The things we have discussed in this section can be summarized as follows;
Inverting amplifier and non-inverting amplifier both are negative feedback op-amp circuits
Non-inverting amplifier the input signal is applied to non-inverting pin
Inverting amplifier the input signal is applied to the inverting pin
Voltage follower is a negative feedback op-amp circuit with unity gain