Power-efficient super class AB OTAs

A family of low-voltage power-efficient class AB CMOS operational transconductance amplifiers (OTAs) is described. It is based on the combination of adaptive biasing techniques and resistive local common-mode feedback (LCMFB), which provides increased dynamic current boosting and gain-bandwidth product (GBW). The different classes of AB OTA topologies presented result from the combination of various adaptive biasing schemes and LCMFB. A 0.5-μm CMOS implementation of three different OTAs shows enhancement factors of slew-rate and GBW up to 280 and 3.6, respectively, for an 80-pF load, compared to a conventional class A OTA with the same quiescent currents and supply voltage. The overhead in area, noise, and static power consumption, is minimal.