| 摘要 |
PURPOSE:To prevent inoperating state from being generated even when optical noise or an excess input comes from a remote control transmitter by providing a switching circuit composed of a transistor(TR) resistance or a diode increasing its current depending on a current flowing to a photodetector. CONSTITUTION:When the photodetector 2 receives an optical signal from a transmitter, a potential difference is generated across the photodetector 2 with a current flowing to the photodetector 2 and when the voltage reaches nearly the minimum driving bias voltage of an amplifier circuit 1, a diode 27 connected across the resistor 7 via a resistor 25 is momentarily conductive and the current is supplied to the photodetector 2 via the resistors 7, 25 to keep the activation of the amplifier circuit 1. Moreover, when a further large input is given and the potential difference generated across the photodetector 2 reaches nearly the minimum driving bias voltage of the amplifier circuit 1, a diode 26 connected across the resistor 25 via a resistor 28 is conductive and the current is supplied to the photodetector 2 via the resistors 7, 25, 28. That is, the inoperating state of the amplifier circuit 1 is prevented by selecting the resistance of the resistors 7, 25, 28. |
