Negative feedback

TL;DR: Negative feedback is an essential component of control systems and is illustrated with an electronic voltage amplifier. It involves the adjustment of the amplifier's frequency response and reduction of distortion.

Abstract: Negative feedback is an essential constituent of any control system. It is illustrated for the case of an electronic voltage amplifier. Formal definitions are given of positive and negative feedback. Feedback can be used to adjust the amplifier's frequency response. Distortion, meaning generation of new and unwanted frequencies (harmonics, sums, differences), is reduced by a factor equal to the “return difference”.