Variable gain feedback amplifier circuit apparatus and method therefor

摘要

A variable gain feedback amplifier circuit comprising a degenerated common emitter circuit coupled to an emitter follower circuit, an output of the emitter follower circuit being coupled to an input of the degenerated common emitter circuit via a variable feedback impedance. An automatic gain controller is coupled to the variable feedback impedance in order to reduce a closed loop gain of the variable gain feedback amplifier circuit when required. The degenerated common emitter circuit also comprises a variable emitter impedance that is also controlled by the automatic gain controller so as to counteract a lowering effect of a reduction in the variable feedback impedance on the open-loop gain of the variable gain feedback amplifier circuit.