A monolithic CMOS audio amplifier with an output stage negative supply rail provided by a charge pump

摘要

A monolithic CMOS audio amplifier for an earthed load comprises an input stage 1 fed by a single positive supply 4 and an output stage 3 fed by 4 and by a negative supply 6 provided by charge pump CP. The effect of charge pump ripple is reduced by applying the generated negative voltage to the output stage only. Negative feedback around the amplifier further reduces the effect of ripple. No output coupling capacitor is required to feed a grounded speaker. The output stage may include NMOS devices possessing a triple-well structure.