| 摘要 |
PURPOSE:To prevent a residual sound from being generated at the time when power is turned off, by rapidly discharging a ripple removal capacitor provided to an initial-stage amplifier circuit. CONSTITUTION:The output of an initial-stage amplifier circuit formed of transistors TRQ1 and Q2 is inputted to A-class large-amplitude amplifying TRQ4, whose output drives B-class PP output circuit 1. Here, TRQ7 is provided which has its emitter connected to the terminal of power-ripple removal capacitor C1 and its base applied with bias voltage Vb obtained by Zener diode Z and resistance R9. This bias voltage applies a reverse bias between the base and emitter of TRQ7. As a result, TRQ7 is rapidly turned on by detecting the lowering of power voltage Vcc after the power is cut off to discharge capacitor C1, thereby stopping the operation of the initial-stage circuit. Therefore, the generation of a residual sound can be prevented. Additionally, a hop sound can also be prevented. |
