| 摘要 |
PURPOSE:To facilitate the control to make an output voltage constant by connecting two resistors in series between a photodetector and earth, and inputting an output signal of a comparator receiving a voltage across a resistor connecting to the earth level to a preamplifier. CONSTITUTION:A voltage across a resistor R2 connecting to the earth side in two resistors R1, R2 connected in series between an avalanche photodiode APD 1 and earth, the voltage is compared with an optional reference voltage of the comparator 5 and a high or a low level signal is outputted from the comparator 5. An output signal of the comparator 5 is inputted to a preamplifier 2 to control the gain of the preamplifier 2 thereby preventing the production of distortion due to saturation of the preamplifier 2 and the control to make the output voltage of an equivalent device 3 constant is facilitated. |
