A high gain low offset amplifier with rail-to-rail inputs

To fit some applications like in Power Management IC (Integrated Circuit), ahigh gain low offset BiCMOS op amp was proposed in this paper. A complementary input stage was adopted to meet a rail-to-rail ICMR (Input Common-Mode Range). And a special circuit configuration was introduced into the rail-to-rail amplifier to keep its gain constant. Simulation showed that the variation of gmwas maintained within 2% over the whole input range. Meanwhile, by using bipolar input stage and current compensating circuit, the offset voltage of the op amp was reduced to less than 0.5mV.