What is the closed-loop gain of a voltage follower?

What is the closed-loop gain of a voltage follower?

• A. Zero
• B. -1
• C. One
• D. Undefined

Answer: (C)

A voltage follower acts as a unity-gain buffer, so the closed-loop gain is one. In this setup the output is fed back directly to the inverting input while the input signal is applied to the non-inverting input. The negative feedback drives the op-amp so that the voltages at the two inputs are essentially equal (Vin ≈ Vout). Since the output tracks the input, the gain Vout/Vin is approximately 1. In an ideal op-amp with infinite open-loop gain, the equality is exact, giving a gain of exactly one; in real devices there is a tiny error due to finite gain, but it remains very close to unity. This configuration also means no phase inversion and provides high input impedance with low output impedance. Other options would imply no output, inversion, or an undefined condition if the feedback were broken.

A voltage follower acts as a unity-gain buffer, so the closed-loop gain is one. In this setup the output is fed back directly to the inverting input while the input signal is applied to the non-inverting input. The negative feedback drives the op-amp so that the voltages at the two inputs are essentially equal (Vin ≈ Vout). Since the output tracks the input, the gain Vout/Vin is approximately 1. In an ideal op-amp with infinite open-loop gain, the equality is exact, giving a gain of exactly one; in real devices there is a tiny error due to finite gain, but it remains very close to unity. This configuration also means no phase inversion and provides high input impedance with low output impedance. Other options would imply no output, inversion, or an undefined condition if the feedback were broken.