Where is the feedback voltage applied in a typical op-amp circuit with negative feedback?

Where is the feedback voltage applied in a typical op-amp circuit with negative feedback?

• A. To the negative input of the op-amp and in phase with the input.
• B. To the positive input of the op-amp.
• C. To the output terminal.
• D. To the supply rails.

Answer: (A)

The signal is fed back to the inverting input. This placement creates negative feedback: as the output changes, the portion of it that is fed back into the inverting input counteracts the input signal, driving the difference between the two inputs toward zero. That keeps the op-amp operating in its linear region and fixes the closed-loop gain based on the feedback network, rather than the open-loop gain of the amplifier. In a typical setup, the non-inverting input receives the input signal (or a reference), while the feedback network connects from the output back to the inverting input. If feedback were applied to the non-inverting input, it would tend to reinforce the input, creating positive feedback and risking saturation or instability. Feedback to the output or to the supply rails isn’t used as the summing path that stabilizes the amplifier.

The signal is fed back to the inverting input. This placement creates negative feedback: as the output changes, the portion of it that is fed back into the inverting input counteracts the input signal, driving the difference between the two inputs toward zero. That keeps the op-amp operating in its linear region and fixes the closed-loop gain based on the feedback network, rather than the open-loop gain of the amplifier.

In a typical setup, the non-inverting input receives the input signal (or a reference), while the feedback network connects from the output back to the inverting input. If feedback were applied to the non-inverting input, it would tend to reinforce the input, creating positive feedback and risking saturation or instability. Feedback to the output or to the supply rails isn’t used as the summing path that stabilizes the amplifier.