| 摘要 |
PURPOSE:To prevent the destruction due to an excess current by providing a transistor (TR) becoming an inverting characteristic through the voltage level increase at an output terminal of an amplifier circuit to block the supply of a drive current to a push-pull amplifier circuit. CONSTITUTION:When a +Vcc is applied to a terminal No. 4 due to an unexpected event, although the collector potential of a TRQ10 for push-pull amplifier and the emitter potential of a TRQ12 are increased, A TRQ15 prevents an excess base current from flowing to a TRQ10, a detection signal Vc from a circuit block 3b is inputted to a drive circuit, TRs Q41, Q51, Q52, Q53 are turned on from lines l3, l4, a base current to drive the TRQ10 is shut off completely by the cut-off of currents ID, IE and the connection of the TRQ52 to a common and push-pull amplifier TRs Q7, Q8, Q9, Q10 are protected.
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