A digital process compatible high-drive CMOS op amp with a rail-to-rail input and output ranges

Digital compatible CMOS buffer amplifiers which achieve a high degree of linearity along with heavy load (300 Ω||100 pf) driving capability from a single-5-V supply are presented. It is shown that with a novel design of the class AB output stage, one would be able to use the gate channel capacitances from standard MOSFETs as the compensation capacitors for the op amp, which would achieve the similar area efficiency as using double-polysilicon capacitors in 2-poly processes. This op amp has good performance characteristic in terms of CMRR, PSRR, and noise level, which makes it very useful in many high-performance circuit applications. The variation of small-signal voltage gain versus input CMR are similar to a recently reported result. Circuit details add measured results which clearly show improvement over previously reported results are given