RLC Circuits with Feedback

Abstract

Feedback is of paramount importance in engineering and especially in circuits. By monitoring a point and making decisions accordingly we can generate new circuits that do useful functions. In this chapter we show how spectral techniques can work with feedback circuits seamlessly. First we start with simple feedback circuits and identify effective input and output impedance. Then we examine the impact of the feedback network assumed here to be a low-pass filter. Then we do analysis in the frequency domain where we calculate output voltage. Then we go back to the time domain by doing inverse transform and figuring step response. Finally we examine impact of output cap on output impedance and output voltage. In all cases we unfold the relevant impacting parameters, such as feedback gain, DC resistance, and feedback filter on system performance such as DC droop, bandwidth, and ramp rate. We dissect the resulting poles/zeroes and tie them to the time domain. On the physical side we tie feedback to power delivery and to voltage regulators. In the end we prove that spectral (and convolution) techniques apply equally well to feedback networks as they did for passive RLC networks.