A programmable rail-to-rail constant-g/sub m/ input structure for LV amplifier

Abstract

We proposed a novel technique for low voltage rail-to-rail constant-g/sub m/ input stages, which does not depend on the operation regions of the MOS transistors. An op amp was designed to demonstrate the new idea using MOSIS AMJ 1.2 /spl mu/m technology. A 2.5 MHz unity-gain bandwidth with 61/spl deg/ phase margin was achieved when driving 10 k/spl Omega/ and 10 pF load, with 240 /spl mu/A current consumption and a power supply of 3 V. The g/sub m/ variation of the input stage is within /spl plusmn/3% from rail-to-rail. By changing the bias current, the unity-gain bandwidth could be programmed from 90 kHz to 3 MHz.