Power amplifier circuit employing field-effect power transistors

Claim 1

Amplifying apparatus comprising: first and second terminals for receiving operating potential therebetween; input and output terminals for receiving and supplying respective time-varying signals; first and second field-effect transistors of like channel conductivity, each having a conductive channel between its drain and source electrodes and each having a gate electrode; means for coupling the drain and source electrodes of said first transistor to said first and output terminals, respectively; means for coupling the drain and source electrodes of said second transistor to said output and second terminals, respectively; means for applying the time-varying signals received at said input terminal to the respective gate electrodes of said first and second transistors including means for inverting the sense of the time-varying signal applied to the gate electrode of one of said first and second transistors with respect to the sense of the time-varying signal applied to the gate electrode of the other of said first and second transistors; biasing means responsive to the voltages at the drain and source electrodes of said first transistor for developing a substantially direct current biasing voltage with respect to the voltage at the source electrode of said first transistor; and means for applying said biasing voltage to the gate electrode of said first transistor including a resistance for coupling said biasing voltage to the gate electrode of said first transistor and switching means coupled across said resistance for completing a conductive connection thereacross responsive to said biasing voltage exceeding the potential at said first terminal.