Amplifier circuit with a stabilized bias in its output stage

Abstract

An amplifier circuit with a stabilized bias in its output stage includes a push-pull type output-circuit having a first transistor and second transistor connected to each other in Darlington connection, a third transistor and a fourth transistor respectively operating complementarily with the first transistor and the second transistor. The third transistor and fourth transistor are connected to each other in Darlington connection, and the second transistor and fourth transistor are connected in series as output stage transistors between terminals of a DC power supply source. The amplifier circuit further includes a current detection circuit having current detection resistance inserted between either the first transistor or the third transistor and the DC power supply source and detecting idling current of either the first transistor or the third transistor by means of terminal voltage of the current detection resistance, and a biasing circuit responsive to output of the current detection circuit for controlling the idling current of either the first transistor or the third transistor in a negative feedback fashion.

Dependencies are inferred from the claim text.