Push-pull audio amplifier

Claim 1

In a push-pull class B audio amplifier having upper and lower input terminals and upper and lower output terminals related to ground and defining upper and lower legs which are active during alternate half-cycles of an alternating input signal, the combination comprising first and second transistors in the upper leg connected in Darlington pair configuration in which (a) the base of the first transistor is connected to the input terminal, (b) the emitter of the first transistor is connected to the base of the second transistor, (c) the collectors are connected together to form a load circuit with the emitter of the second transistor, said upper leg including an auxiliary transistor having its output circuit connected in shunt between the base of the second transistor and ground, the lower leg arranged as the mirror image of the upper and including a Darlington pair and a similarly connected auxiliary transistor, a push-pull output transformer having its input windings connected to the respective Darlington load circuits, the input circuits of the auxiliary transistors being coupled to respective input terminals so that the auxiliary transistors are non-conducting during the conductive half-cycle of their associated Darlington pair but provide a low resistance path to ground during the inactive halfcycle thereof for promptly draining charge from the associated Darlington pair during the inactive half cycle to preclude any conduction thereof whatsoever during the inactive half-cycle.