Folded cascode high voltage operational amplifier with class ab source follower output stage

Abstract

An operational amplifier comprises multiple stages. A differential input stage that includes an adaptive high voltage differential pair generates up and down output currents in response to up and down input voltages. The differential input stage includes adaptive common input high voltage (HV) bias. An intermediate stage converts the up and down output currents into a first output voltage signal. The intermediate stage includes a folded cascode arrangement. The intermediate stage is biased by fixed voltage bias signals. The intermediate stage also includes unaffected slew rate stability compensation and a combined split stability compensation. An output stage includes a class AB source follower driver that generates a second output voltage signal in response to the first output voltage signal. The output stage is biased with an adaptive push-pull source follower output HV bias. The output stage includes feed-forward slew rate enhancement. A local power supply pre-filter provides a filtered local high voltage to the differential input stage and stages that provide the fixed and adaptive voltage bias signals.