In a negative-feedback op-amp circuit, the input differential voltage tends to

In a negative-feedback op-amp circuit, the input differential voltage tends to

• A. Very small, approaching zero
• B. Large and positive
• C. Large and negative
• D. Exactly zero

Answer: (A)

Negative feedback makes the op-amp drive its output so that the voltages at its two input terminals are nearly the same. The loop continuously corrects any small difference, and because the amplifier has a very large open-loop gain, even a tiny input error is enough to produce a change in output that pulls the inputs closer together. In an ideal model with infinite gain, the differential input would be exactly zero; in real devices it is extremely small, not exactly zero. So the input differential voltage tends to a very small value, approaching zero.

Negative feedback makes the op-amp drive its output so that the voltages at its two input terminals are nearly the same. The loop continuously corrects any small difference, and because the amplifier has a very large open-loop gain, even a tiny input error is enough to produce a change in output that pulls the inputs closer together. In an ideal model with infinite gain, the differential input would be exactly zero; in real devices it is extremely small, not exactly zero. So the input differential voltage tends to a very small value, approaching zero.