Comparative analysis of two versions of the Miller OA based on a systematic design method

Abstract

This paper presents a clear comparison between two Operational Amplifiers (OAs) based on the same structure -the classical Miller OA -but with different solutions for dealing with the right-half plane zero (RHZ) associated to it: in one case, by inserting a resistor in series with the compensating capacitor and in the other case by using a current buffer, implemented by a cascoded transistor, to block (partially) the feedforward path causing the zero. Both OAs are designed following a systematic approach, that considers a wider set of specifications than the standard design methods reported in the literature. For a fair comparison both OAs were designed for the same set of specifications, including same power consumption and area: GBW of 500MHz for I DD =500uA, PM=60dgr for C L =1pF. Simulation results validate the design of these OAs, implemented in a standard 0.15um CMOS.