| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical receiver circuit capable of receiving an optical signal without a saturated diode even if photoelectric current increases. SOLUTION: The optical receiver circuit 20 is composed of the optical receiving diode D1, an operational amplifier AMP1, a feedback resistor Rr, a low-pass filter 26, a current detecting part 28, a current source 29 and a constant-voltage source 31. In the case where sunlight directly irradiates the optical receiving diode D1, a photoelectric current flowing in the cathode of the optical receiving diode D1 is to be the sum a DC current by sunlight components and an AC current by optical signal components. Since a collector current which is equivalent to the above DC current is flown in the collector of an NPN transistor forming the current source 29, only signal current flows in one terminal side of the operational amplifier AMP1 from the anode of the light receiving diode D1. As a result, voltage drop in the feedback resistor Rr is restrained at a small, and the optical receiving diode D1 does not reach a saturating region. |
