| 摘要 |
PURPOSE:To simplify the constitution of the frequency conversion circuit of the optical current, by inputting the output of a photodiode to an oscillator comprising a current mirror circuit and a capacitor through a differential amplifier. CONSTITUTION:When a capacitor 22 is charged by the optical current (a current ISH from a constant current source 21) and the voltage at a terminal 210 exceeds the inverted output voltage VHT of a high trip inverter 24, an RS-FF comprising two input negative AND circuits 28 and 29 is reset, and an output 211 is inverted from H to L. Therefore the output of an inverter 27 is inverted from L to H and an FET23 is condcuted. Then the voltage Vc at a terminal 210 is decreased by the time constant determined by the capacity of the capacitor 22 and the resistance of the Tr23 down to the value lower than the inverted voltage of the inverter 25. Then an inverter 26 is reset through the inverter 25, and the Tr23 is cut off. The capacitor C repeates the cahrge and discharge by said cycle. Therefore the constitution of the frequency circuit of the optical current is simplified. |
