Robust and universal constant-g/sub m/ circuit technique [operational amplifiers]

A robust and universal circuit technique to maintain a constant transconductance, g/sub m/, in rail-to-rail amplifiers based on input stages made up of parallel-connected complementary differential pairs, is presented. The technique is universal, since it is valid regardless of the g/sub m//I/sub D/ characteristic of input devices. Also, the accuracy does not depend on any condition for matching n- to p-channel input transistors, which makes the technique robust. Experimental results obtained from a 0.8 /spl mu/m CMOS test-chip prototype, are given.