Analysing the stability of series-shunt circuits based on voltage- and current- feedback OpAmps through SPICE AC simulations

Two methods for determining the loop gain of OpAmp-based circuits with series-shunt feedback through simulations are analyzed and compared: the standard method — that involves breaking the feedback loop by inserting an independent voltage source with DC=0 and AC=1 — and a more precise method, based on the Rosenstark theorem. Only the cases for the traditional (voltage-feedback) and the current-feedback OpAmps are discussed in the paper but the conclusions can be extended to other types of amplifiers.