Digital-compatible high-performance operational amplifier with rail-to-rail input and output ranges

This paper presents a CMOS buffer amplifier which operates on a single 5-V power supply. The uniquely symmetrical design adds the following advantages: rail-to-rail linear, symmetrical operation at both the input and output; the output stage allows the use of gate channel capacitors of standard MOSFET´s as the compensation capacitor saving die area from 80%~93% in a standard single polysilicon digital process; large gain-bandwidth product; high power supply rejection ratio; good common-mode rejection ratio; and easy compact layout suitable for design automation (layout as a parametric cell, allows easy adaption to changing processes). The buffer is capable of driving 300 Ω||100 pF with a loaded gain-bandwidth product of more than 4 MHz and a fully loaded slew rate of greater than 4 V/μS