Two pole, high speed operational amplifier modelling, methods and techniques

In this paper an initial review of existing techniques for two stage operational amplifier modelling is described and the deficiencies of these techniques identified. In particular, the commonly used Miller´s Approximation is shown to present a quite significant error when applied to high frequency op-amp designs. Two new accurate equivalent models for two pole amplifier architectures are then presented. These new models facilitate precise prediction of pole locations of both input and output stage dominant pole amplifiers, irrespective of the value of feedback capacitance and second stage transconductance. They also feature design flexibility and are readily applied to two pole operational amplifiers. An example of a two-stage CMOS operational amplifier design is presented to demonstrate the application of the new equivalent circuits