| 摘要 |
PROBLEM TO BE SOLVED: To provide a light receiving circuit that has a small gain reduction even to a very small input light. SOLUTION: A constant current source 9 is added to a resistance coupling amplifier circuit consisting of resistors R1, R2, a capacitor 4 and an operational amplifier 7 whose noninverting input is connected to one terminal of a load resistor 2 connected in series with a light receiving element 1. The constant current source 9 supplies a current to the resistors R1, R2 even when a zero level is given to the noninverting input terminal to allow the operational amplifier 7 to produce a prescribed voltage as its output. Since the output of the operational amplifier 7 reaches a level not being zero, the light receiving circuit has a small gain reduction. |
