Supply-adaptive rail-to-rail CMOS OPAMP

A supply-adaptive rail-to-rail CMOS OPAMP is implemented with a standard 0.6-micron CMOS technology of CSMC, China. The external supply voltage ranges from 2.1V to 3.2V while stabilized internal supply voltage is 1.7V. With the internal supply adaptive to the crossing-point condition, a constant input G/sub m/ is achieved within 10% point-to-point maximum variation in the whole range of common-mode (CM) input. Rail-to-rail output stage with two folded meshes and feedback class-AB control minimizes the supply voltage down to V/sub gs/+2V/sub ds/ and the current, respectively.