Feedback Amplifier Theory
DOI link for Feedback Amplifier Theory
Feedback Amplifier Theory book
Feedback, whether intentional or parasitic, is pervasive of all electronic circuits and systems. In general, feedback is comprised of a subcircuit that allows a fraction of the output signal of an overall network to modify the effective input signal in such a way as to produce a circuit response that can differ substantially from the response produced in the absence of such feedback. The disadvantages of negative feedback include gain attenuation, a closed-loop configuration that is disposed to potential instability, and, in the absence of suitable frequency compensation, a reduction in the open-loop gain-bandwidth product. Even positive feedback is possible if substantive negative feedback is applied around an openloop amplifier for which more than two poles significantly influence its frequency response. Constant feedback applied around an underdamped two-pole open-loop amplifier yields a severely underdamped closed-loop configuration. Equation underscores the desirability of achieving an open-loop dominant pole frequency response in the design of a feedback network.