Low voltage rail-to-rail operational amplifier based on flipped voltage followers

A low voltage differential pair or flipped differential pair is presented. The design of a rail to rail op-amp with an input stage using complementary flipped differential pairs and a novel gm control circuit is discussed. Simulation results in 0.5/spl mu/m CMOS technology with nominal PMOS and NMOS threshold voltages of 0.75V and -0.95V show input/output rail-to-rail operation with a 1.9V single supply. This supply is two drain-source saturation voltages lower than for rail op amp using conventional complementary differential pairs.