| 摘要 |
PROBLEM TO BE SOLVED: To provide a light detecting device having high light detection sensitiv ity by decreasing noises as much as possible. SOLUTION: The light detecting device comprises a light detector 1, a JFET 2 which reads detection signals of the light detector 1, an OP amplifier 3 which amplifies the signals read by the JFET 2, a feedback circuit which returns the output of the OP amplifier 3 to the JFET 2 through a feedback capacity 4, and a reset circuit which conduct a reset by discharging charges of the feedback capacity 4 through a MOSFET S1. A drain or source of the MOSFET S1 for reset is applied a voltage through a resistor R2 which is the same level of the gate voltage of the JFET 2, and a switch S2 is connected through a resistor Rl between a drain or source of the MOSFET S1 and the feedback capacity 4 which is controlled to be off if the MOSFET S1 is off, and to be on if the MOSFET S1 is on. COPYRIGHT: (C)2004,JPO
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