| 摘要 |
PURPOSE:To obtain a stable output even in case no photodetection signal is avialable with the output of an integrated circuit IC kept at 1/2 output of a voltage amplifying circuit, by connecting a DC source to the joint of a peak holding circuit and a capacitor in the IC that supplies the photodetection signal and delivers the digital signal. CONSTITUTION:A current source 17 is connected to the joint between a feedback resistance 12 and a diode 13 and a peak holding capacitor 14 in a peak holding circuit 9. When no input of the circuit 9 is obtained, the charging current of the capacitor 14 does not flow via the diode 13. Thus the voltage of the capacitor 14 is decided by the source 17 and feedback resistances 11 and 12. Then the capacitor 14 is shifted by the value of said decided voltage. When the input of the circuit 9 is increased, said charging current is reduced by the value obtained by the source 17 and therefore flows also via the diode 13. Under such conditions, an inverse amplifier 10 works so that its voltage is set at 1/2 output of a voltage amplifying circuit 5. Thus the output of a voltage comparator 15 is stabilized. Furthermore the effect of the source 17 is invalidated when the input of the circuit 9 is large. Therefore the conversion is possible into the digital output with 50% of an input waveform. |
