The lowest gain that can be obtained from a noninverting amplifier with feedback is 1. When the noninverting amplifier is configured for unity gain, it is called a voltage follower because the output voltage is equal to and in phase with the input. In other words, in the voltage follower the output follows the input.
Although it is similar to the discrete emitter follower, the voltage follower is preferred because it has much higher input resistance, and the output amplitude is exactly equal to the input. To obtain the voltage follower from the noninverting amplifier, simply open the input resistance R1 and short the feedback resistor Rf.
Figure shows the circuit diagram of a VOLTAGE FOLLOWER, in which the output voltage is fed back to the inverting terminal of operational amplifier (op amp); consequently the gain of the feedback circuit is 1.
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