Common mode rail-to-rail amplifier with a constant transconductance

摘要

An amplifier includes two complementary differential input stages and a first current source that is switched as a function of the input voltage of the amplifier in order to render active one or the other of the input stages by establishing the quiescent current of the input stage. A folded cascode stage has two cascode transistors whose currents are determined by a bias voltage of these transistors and reduced by the currents circulating in the output branches of a first of the differential input stages. Circuitry switched at the same time as the first current source for maintaining a constant current in the cascode transistors when one of the differential stages changes between an active state and an inactive state.