Amplifier with input referred common-mode adjustment

摘要

A circuit and method control the common-mode potential at an output (17, 18) of a fully differential amplifier (32) by feeding forward a common-mode correction signal through the amplifier. An input signal (VIN+-VIN-) is amplified in the amplifier to produce a differential output signal (VO--VO+) at the output. A common potential of the differential inputs (37, 38) of the amplifier is sensed with a transistor (54, 56) biased to a reference voltage (VCM) and amplified through the amplifier to produce a common-mode correction signal to offset a common-mode component of the differential output signal. A feedback circuit (33-36) is used to develop the common potential from the common-mode component.