Power-amplifying circuit

Abstract

A power-amplifying circuit embodying this invention includes a pre-amplifier stage which comprises two emitter-connected transitors, one of whose bases is supplied with an input signal and an output stage comprising complementary pair of a first transistor of a PNP type and an emitter-grounded second transistor of an NPN type which carry out a class-AB push-pull operation in accordance with the amplitude of a current from the pre-amplifier stage. The power-amplifier circuit of this invention further comprises third transistor for detecting an operating current of the first transistor of the output stage, a fourth transistor which is driven by the third transistor and whose base is connected to the base of the second transistor of the output stage, and fifth and sixth transistors which are connected in such a manner that a sum of the base-emitter voltages of the fifth and sixth transistors is made equal to a sum of the base-emitter voltages of the second and fourth transistors, and through which there flows a current corresponding to a product of the operating currents of the first and second transistors constituting the output stage. A current running through the fifth and sixth transistors is supplied to the pre-amplifier means through a negative feedback path so as to be regulated.

Dependencies are inferred from the claim text.