Class-AB single-stage OpAmp for low-power switched-capacitor circuits

This paper presents a new family of Class-AB operational amplifier (OpAmp) circuits based on single-stage topologies with nonlinear current amplifiers. The proposed OpAmp architecture is mainly characterized by generating all Class-AB current in the output transistors only, exhibiting very low technology sensitivity and avoiding the need of any internal frequency compensation mechanism. Hence, this family of OpAmps are suitable for low-power switched-capacitor circuits and specifically optimized for switched-OpAmp fast on-off operation and multi-decade load capacitance specifications. A complete OpAmp design example integrated in standard 0.18μm 1P6M CMOS technology is supplied with detailed simulation and experimental results. Compared to MOS-only state-of-art Class-AB OpAmp literature, the proposed architecture returns the highest figure-of-merit value.