What are the practical benefits of a voltage follower (unity-gain buffer) in circuit design?

• A. Increases output impedance
• B. High input impedance and low output impedance
• C. Inverts the signal
• D. Requires no power supply

Answer: (B)

A voltage follower acts as a buffer between stages, and its practical benefit comes from how it handles impedance. It presents very high input impedance, so the source is loaded very little; you can connect a source with a small output current capability without pulling its voltage down. It also delivers very low output impedance, allowing the following stage (or a heavy load) to be driven effectively without a big drop in voltage. Because the amplifier is wired for unity gain, the signal amplitude is preserved and there is no phase inversion, which keeps the original waveform intact while isolating the source from the load.

In short, this combination—high input impedance and low output impedance—makes the buffer ideal for preserving the source signal, preventing loading effects, and easing drive of subsequent stages. Note that the buffer does require a power supply to operate, and it does not invert the signal or increase output impedance.