A family of high-swing CMOS operational amplifiers

Abstract

A family of high-swing CMOS operational amplifiers has been developed to maximize the available dynamic range with low supply voltages. Complementary differential pairs are used to achieve an almost rail-to-rail input common-mode voltage range. High linearity is obtained by summing currents so that the small-signal differential-mode voltage gain is constant over the entire input common-mode range. With a 5.0-V power supply, the total harmonic distortion is typically only 1% in a unity-gain configuration with a 4.5-V/sub p-p/ signal. The measured DC offset voltages versus input common-mode range track between the conventional and high-swing versions. These measurements suggest that the commonly feared crossover distortion may not be a problem when the current summation high-swing topology is used. The measured step response characteristics were excellent and exhibited no signs of phase mismatch crossover distortion for high-frequency signals. >