| 摘要 |
A first amplifying transistor is connected between a first supply terminal and an output terminal, the latter being grounded via a loudspeaker system, and another such transistor between a second supply terminal and the output terminal. A first and a second drive transistor are Darlington connected respectively to the first and the second amplifying transistor. A first biasing circuit is connected between the first supply terminal and the base of the first drive transistor, and a second biasing transistor between the second supply terminal and the base of the second drive transistor. In order for an idling current of stable magnitude to flow immediately when the amplifier circuit is powered on, without need for preadjustment of circuit elements, an improved third biasing circuit is connected between the bases of the two drive transistors. The third biasing circuit comprises two biasing transistors and a serial circuit of two resistors. One of the biasing transistors has its collector connected to the base, and its base to the emitter, of either of the two drive transistors, thereby forming a negative feedback circuit.
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