Using moderate inversion to optimize voltage gain, thermal noise, and settling time in two-stage CMOS amplifiers

This paper describes the use of moderate inversion for selected MOS transistors in a two-stage CMOS amplifier to achieve high voltage gain, low thermal noise, and fast settling time at minimum power consumption. A detailed circuit analysis, implemented in a MATLAB design tool, is presented to find the optimal inversion level for MOS transistors. The analysis and design tool are illustrated for a fully differential, two-stage, 0.5-μm CMOS amplifier having voltage gain >; 80 dB, input-referred thermal noise voltage