In an op-amp circuit using negative feedback, which effects are typically observed?

• A. In op-amp circuit using negative feedback, increased linearity and bandwidth, reduced gain variation.
• B. It increases distortion.
• C. It increases input bias current.
• D. It decreases input impedance.

Answer: (C)

Negative feedback makes the amplifier operate more like the external network designed around it, pulling the output toward the desired level and reducing the influence of the device’s own non-idealities. Because the loop continuously corrects errors, the overall response becomes more linear, so distortion is suppressed and the amplifier behaves more predictably over a range of inputs.

This same feedback also broadens the usable frequency range. The closed-loop gain is set by the feedback network, not solely by the op-amp’s own gain inside the package. With negative feedback, the system can maintain its intended gain while responding faster to changes, effectively increasing the bandwidth compared to what the open-loop device would offer. Since the gain is stabilized by the feedback, variations in the op-amp’s internal gain due to temperature, aging, or power supply tend to have a smaller effect on the actual closed-loop gain.

Regarding input bias current, that parameter is tied to the input transistor structure and is not inherently increased by applying negative feedback. Similarly, input impedance can vary with the configuration, but the most consistent, general outcome of negative feedback is improved linearity, wider bandwidth, and more stable gain, rather than a universal increase in bias current or a definite decrease in input impedance.