Which statement best describes the essential feedback path in a voltage follower?

Which statement best describes the essential feedback path in a voltage follower?

• A. The output is fed back to the inverting input
• B. The output is fed back to the noninverting input
• C. There is no feedback path
• D. Feedback uses a resistor network to set gain

Answer: (A)

The key idea is that a voltage follower uses negative feedback from the output back to the inverting input. With the input signal applied to the noninverting input, the op-amp will adjust its output so that the two inputs sit at the same voltage. That makes the closed-loop gain effectively 1, so the output follows the input closely while still providing low output impedance. If the feedback were instead to the noninverting input, the feedback would be positive, causing the output to push toward a rail rather than settle at the input value. Without any feedback, the op-amp would operate in open-loop with huge gain and would saturate. Using a resistor network to set gain would also destroy the unity-gain behavior, giving a gain different from one. Therefore, feeding the output back to the inverting input is what creates the stable, exact follower action.

The key idea is that a voltage follower uses negative feedback from the output back to the inverting input. With the input signal applied to the noninverting input, the op-amp will adjust its output so that the two inputs sit at the same voltage. That makes the closed-loop gain effectively 1, so the output follows the input closely while still providing low output impedance. If the feedback were instead to the noninverting input, the feedback would be positive, causing the output to push toward a rail rather than settle at the input value. Without any feedback, the op-amp would operate in open-loop with huge gain and would saturate. Using a resistor network to set gain would also destroy the unity-gain behavior, giving a gain different from one. Therefore, feeding the output back to the inverting input is what creates the stable, exact follower action.