Apparatus and method for a turn around stage having reduced power consumption, Class AB behavior, low noise and low offset

摘要

The invention includes a differential input stage that is coupled to a turn around stage with a differential output. The input common mode voltage range is independent of the output common mode voltage range and the electronic circuitry is suited for use with other circuits such as an amplifier. The circuitry provides Class AB operation with quiescent and bias currents that are significantly less than the maximum output signal current so that overall power consumption is significantly reduced. The biasing of the output transistors in the turn around stage is floated and the invention is well suited for use with other circuits that require an input stage that can operate between the rails of a voltage supply. Also, the amount of noise is reduced and the offset performance of the circuit is improved by cross coupling the emitters of separate transistors employed to bias the output transistors in the turn around stage. Additionally, a complementary input stage can receive a differential input signal with a common mode voltage that is at, or between, the rails of the voltage supply. Further, a pair of turn around stages are adapted to combine the currents outputted by the complementary input stage.