Design procedures for three-stage CMOS OTAs with nested-Miller compensation

Design procedures for three-stage CMOS operational transconductance amplifiers employing nested-Miller frequency compensation are presented in this paper. After describing the basic methodology on a Class-A topology, some modifications, to increase swing, slew-rate and current drive capability, are subsequently discussed for a Class-AB solution. The approaches developed are simple as they do not introduce unnecessary circuit constraints and yield accurate results. They are hence suited for a pencil-and-paper design, but can be easily integrated into an analog knowledge-based computer-aided design tool. Experimental prototypes, designed in a 0.35-[micro]m technology by following the proposed procedures, were fabricated and tested. Measurement results were found in close agreement with the target specifications. Index Terms--CMOS, multistage amplifiers, nested-Miller compensation, operational transconductance amplifiers (OTAs).