Class-AB SiC CMOS power opamp with stable voltage gain over wide temperature range

A class-AB silicon carbide CMOS power operational amplifier with stable open-loop voltage gain over a wide temperature range is presented. A temperature-insensitive voltage reference is designed to provide bias voltages for the operational amplifier. An extra bias circuit is also developed such that the voltage gain of the operational amplifier can be insensitive to threshold voltage and mobility variations. A class-AB output stage combined with a novel adaptive biasing scheme is developed to produce a full rail-to-rail output swing and low output resistance of 90 Omega at 75 degrees C. A nested Miller-compensated topology is also incorporated to provide a phase margin of 60 degrees. The DC gain of the operational amplifier only experiences a 1.265dB variation over a temperature range of 75 to 300 degrees C and a 3.387dB variation from V-DD(-V-SS) = 5.0V to V-DD(-V-SS) = 20V. This operational amplifier is ideal for use as a voltage buffer or power amplifier intended for high temperature operation.