Device with common mode feedback for a differential output

摘要

A functional circuit such as an OP-amp has a differential output. A common mode signal at the differential output is adjusted by means of a common mode feedback circuit coupled between the differential output and the common mode adjustment input. The common mode feedback circuit contains IGFETs, each having a channel and a backgate, each connection of the differential output being coupled to the backgate of a respective one of the IGFETS. Thus the voltages at the outputs influence the current through the channel. The sum of the currents determines a feedback to the common mode control input.