ABSTRACT
In electronic circuits and systems, feedback will be defined as a process whereby a signal proportional to the system’s output is combined with a signal proportional to the input to form an error signal that affects the output. Nearly all analog electronic circuits use feedback — implicitly as the result of circuit design (e.g., as from an unbypassed BJT emitter resistor) or explicitly by a specific circuit network between the output and the input nodes. A circuit can have one or more specific feedback loops. However, in the interest of simplicity, the effects of a single feedback loop on circuits with single inputs will be considered. The four categories of electronic feedback and the feedback that can make an electronic system unstable (deliberately, as in the design of oscillators) or stable will be shown. The effects of feedback on amplifier frequency response, gain, noise, output and input impedance, and linearity will also be discussed.
