Micropower class AB voltage followers with simple quiescent current control

Abstract

Five class AB CMOS voltage followers are described. They are modifications of the conventional super source follower, and allow improved dynamic performance, increased signal swing, accurate control of quiescent currents, and no penalty by the inclusion of class AB operation in terms of quiescent power consumption, circuit complexity or supply voltage requirements. Measurement results for a 0.5μm CMOS test chip prototype show a slew rate enhancement factor of about 20 as compared with the conventional super follower, for the same bias current and supply voltage.