POWER SUPPLY CIRCUIT OF AMPLIFIER

PURPOSE:To improve the slow operation of a switch circuit approximately at a high turn-on level by permitting the switch circuit which switches the collector of a power transistor (TR) to a high potential by the output of a high- level detecting circuit. CONSTITUTION:A signal applied to an input terminal 1 is voltage-amplified by TRs Q1 and Q2 power-amplified by TRs Q3 and Q4 to drive a load connected to an output terminal 2 on push-pull basis. The amplified signal is further supplied to the high-level detecting circuit 14 consisting of a cpacitor C1 and resistors R4 and R5; once the circuit 14 operates, the switch circuit 15 turns on to raise the collector voltage Vc of the TRQ5 to a high-potential power voltage +BH and also to feed the power voltage +BH back to the base of a TRQ9 positively through a Zener diode D15, resistance R11, and diode D13. Thus, the slow operation of the circuit 15 is improved to stabilize the operation. Further, the circuit 16 is the same.