Historically, negative feedback in electronics was developed to stabilize and linearize the response of circuits. None of the characteristic curves of vacuum t

Historically, negative feedback in electronics was developed to stabilize and linearize the response of circuits. None of the characteristic curves of vacuum tubes and transistors would make you think that there was anything linear about them. However, passive components such as resistors and capacitors are quite linear and stable. So the trick with feedback is that the feedback network defines the response of the circuit despite using potentially nonlinear and unstable gain elements. This was of vital importance for making important circuits, like amplifiers for telephony, predictable, reliable, and reproducible. If you design something like a basic analog filter using op amps, and model its behavior under the assumption of linearity, the actual behavior of the circuit will resemble the model behavior to an uncanny degree. But naturally, terminology is not precise. For instance the term "linear" is used to describe things like power supplies and voltage regulators, in contrast to "switchmode" circuits. A "linear power supply" means a particular thing that has little to do with linearity.