| 摘要 |
PURPOSE:To eliminate a pop noise when a power supply is turned on and off by a method wherein a switch means is installed between a high-voltage power supply and a voltage amplifier circuit. CONSTITUTION:A switch means 156 is provided with an IGBT (an insulated-gate bipolar transistor) 158 as a switching element and with a photocoupler 160. A resistor 166 as well as an emitter and a gate for the IGBT 158 are connected to the output of the photocoupler 160, and a low-voltage power supply (+15V) is connected to its input. When an emitter-to-gate voltage is input to the IGBT 158, the IGBT 158 is set to a continuity state. Since the low-voltage power supply rises at this time, a negative-feedback control circuit 84 is operated according to the input voltage of an input terminal 150, and a controlled voltage is applied to a base for an output transistor 152. Consequently, a voltage which has been stabilized by the operation of the negative-feedback control circuit 84 according to the input voltage of the input terminal 150 is output to an output terminal 154, and a pop noise is not generated. |
