Class AB CMOS Operational Amplifiers with Very High Efficiency

Abstract

A new, simple, yet very current efficient class AB amplifier principle is presented. When used as a differential input stage it features a settling time which is independent of the input signal, and a current efficiency superior to that of any conventional OTA. The same class AB stage can also be used as an output stage with a rail to rail output voltage swing, and a large drive capability. An amplifier with both input and output stages based on this new principle is presented. This amplifier features a gainbandwidth of 310 kHz and a settling time to 0.1% of 2.4 ¿s. It can drive a resistive load of 2500 Ohm in parallel with a capacitive load of 400 pF when operated on a 2.5V/-2.5V power supply, with a quiescent power consumption of only 285 ¿W.