Voltage Follower

Voltage Followers can also be referred to as Unity Gain Amplifiers or Buffer Amplifiers. Refer to the non-inverting amplifier configuration below, we may simply make R1 = 0 and R2 = ∞ to obtain the unity gain amplifier. This circuit is commonly referred to as a voltage follower since the output “follows” the input.

According to the closed-loop gain formula of non-inverting amplifier, we have G = 1+R1/R2. Let R1 = 0 and R2 = ∞, we easily get G ≈ 1. This calculation is not accurate and only for estimation.

Although we call it unity gain amplifier, V_OUT is not exactly equal to V_IN . Actually it has a gain of slightly less than unity due to voltage drop from the wires, as well as op-amp's offset voltage, but the difference is usually small.

In the ideal case, V_OUT = V_IN , R_IN = ∞, and R_OUT = 0.