Transistor power amplifier with dc output voltage stabilization

Claim 1

A transistor power amplifier comprising a voltage amplifier having an input terminal and an output terminal, a current amplifier having an input terminal and an output terminal, means DC coupling said output terminal of said voltage amplifier and said input terminal of said current amplifier and a DC feedback network, said voltage amplifier comprising input and output DC coupled amplifying stages, said stages including first and second transistors respectively each having base, emitter and collector electrodes, first and second terminals at different DC potentials, first and second series connected resistors connected between said first terminal and said base electrode of said input transistor and thereby providing bias for said input transistor, a network connected between said first and second terminals and including said first resistor, a diode network including at least one diode connected in forward biased configuration and a third resistor connected in series with each other, said DC feedback network being connected between said output terminal of said current amplifier and said emitter electrode of said input transistor and including a fourth resistor, said second, third and fourth resistors and the operating current of said input transistor being selected such that the sum of the base-emitter voltage drop of said input transistor and the voltage drops across said second and fourth resistors equals the sum of the voltage drop across said diode network and the voltage drop across said third resistor, whereby the DC potential of said output terminal of said current amplifier equals the DC potential of said second terminal.