0.9 V rail-to-rail constant gm CMOS amplifier input stage

Presented is a 0.9 V rail-to-rail constant g _m CMOS amplifier input stage consisting of complementary differential pairs and a g _m control circuit. The g _m control circuit eliminates the g _m dead zone, which occurs in the conventional rail-to-rail amplifier with ultra-low supply voltages. The proposed amplifier input stage has a constant g _m that varies by plusmn2.3% for rail-to-rail input common-mode levels. To verify the proposed amplifier design, an experimental prototype operational amplifier is also implemented using 0.35 mum standard CMOS technology.