| 摘要 |
An optical signal detection circuit of the present invention comprises (a) a light receiving unit for converting received light into an electric signal, (b) a light-level detection circuit for receiving a photoelectrically converted signal from the light receiving unit, in accordance with a variation of intensity of the received light, detecting an incidence of the light and informing the incidence of the light when a predeterminded time has passed, and (c) an information extracting circuit for receiving the photoelectrically converted signal from the light receiving unit, receiving the information from the light-level detection circuit, and extracting information carried by the received light, and the light-level detection circuit comprises (1) a peak holding circuit for detecting the photoelectrically converted signal and outputting a signal in accordance with the peak-held and photoelectrically converted signal, (2) a reference potential setting circuit for setting a detection level of the photoelectrically converted signal, (3) a discrimination decision circuit for detecting that the photoelectrically converted signal exceeds the detection level, and (4) a capacitor element the first terminal of which is connected to a signal output node of the peak holding circuit and the second terminal of which is connected to a detection-level setting node of the reference potential setting circuit.
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