Symbolic Formulas for Settling Time and Phase Margin of Op-Amp with Arbitrary Number of Poles and Zeros

Abstract

Settling time (ST) and phase margin (PM) of an op-amp with an arbitrary number of poles/zeros are estimated using the approximate pole/zero symbolic expressions. The method is illustrated by finding the symbolic expressions of ST and PM for a fully differential two-stage op-amp in terms of load, feedback, and Miller capacities. In this case the closed loop voltage gain has 8 poles and 7 zeros.