1-V quasi constant-g/sub m/ input/output rail-to-rail CMOS op-amp

An input/output rail-to-rail CMOS operational amplifier with quasi constant small-signal behavior and operating with a 1-V single supply, is presented. Dynamically biased input level shifters are used to extend the amplifier input voltage range. The operation of these common-mode adapters is controlled taking the small-signal response of the amplifier input stage into account. Experimental results on a test-chip fabricated in standard 0.8-/spl mu/m CMOS technology are given.