Electric amplifier

Claim 1

In a system for amplifying an input signal comprising a source of bias potential, a first amplifying element having a first input circuit and a first output circuit and a second amplifying element having a second input circuit and a second output circuit, said first and second amplifying elements being arranged in a push-pull configuration and having the first and second output circuits connected to a common lead so that d.c. current is capable of flowing from the source of bias potential through the first and second output circuits, improved means of setting and adjusting the d.c. current comprising in combination: means for conducting said input signal to the second input circuit; a third amplifying element having a third input circuit, a nonlinear input circuit impedance characteristic, and a third output circuit, said third output circuit of said third amplifying element being connected to the first input circuit; bias means for establishing a bias voltage on the third input circuit in the absence of the input signal; means for conducting said input signal to the third input circuit; and capacitor means connected in series with the third input circuit for changing the d.c. bias voltage on the third input circuit in proportion to the change in magnitude of the input signal, whereby the d.c. current flowing through said first and second output circuits is set at a low level when no input signal is present and the changing d.c. bias voltage is amplified and applied to the first input circuit by the third amplifying element as the input signal increases so that the d.c. current increases and cross-over distortion is reduced.