Which statement about a voltage follower is false?

Which statement about a voltage follower is false?

• A. The ratio between the circuit feedback and input resistors must equal 1
• B. The circuit has unity gain
• C. The output follows the input
• D. There is direct feedback from output to the inverting input

Answer: (A)

A voltage follower is a unity-gain buffer that relies on a direct, negative feedback path from the output to the inverting input. The input signal is applied to the non-inverting input, and the output is forced to match the input because the op-amp drives until V- equals V+. With the output fed back directly, there are effectively no feedback resistors forming a network; the gain is exactly 1 by the very nature of this direct connection. The statement about the ratio of feedback to input resistors being 1 is not applicable here. In a voltage follower there aren’t external feedback and input resistors to form a ratio; the loop gain is set by the direct short from output to inverting input, which yields unity gain. That’s why the other descriptions are correct: the circuit has unity gain, the output follows the input, and there is direct feedback from the output to the inverting input.

A voltage follower is a unity-gain buffer that relies on a direct, negative feedback path from the output to the inverting input. The input signal is applied to the non-inverting input, and the output is forced to match the input because the op-amp drives until V- equals V+. With the output fed back directly, there are effectively no feedback resistors forming a network; the gain is exactly 1 by the very nature of this direct connection.

The statement about the ratio of feedback to input resistors being 1 is not applicable here. In a voltage follower there aren’t external feedback and input resistors to form a ratio; the loop gain is set by the direct short from output to inverting input, which yields unity gain. That’s why the other descriptions are correct: the circuit has unity gain, the output follows the input, and there is direct feedback from the output to the inverting input.