(US5869857-A)      The photodetector includes a gate bias type MOS transistor having an electric charge accumulation pole which accumulates electric charge based on light received with a pn-junction photodiode (71). The gate bias type MOS transistor includes a bias voltage storage pole and a source voltage input pole connected to a voltage source.    An optical signal is output from an output terminal of the MOS transistor based on the potential of the electric charge accumulation pole which is charged using a charging switch. The reference voltage is added to the bias voltage storage pole in response to a charging control signal, using a signal reading switch. The light signal is output from the output terminal through the terminal connected to the output terminal, in response to a reading control signal.    USE -   In facsimile, camera.    ADVANTAGE -   Exhibits large operation range, and sensitivity. Compensates DC offset accompanied by temperature variation. Improves image signal reading rate.    (JP3042617-B2)      The photodetector includes a gate bias type MOS transistor having an electric charge accumulation pole which accumulates electric charge based on light received with a pn-junction photodiode (71). The gate bias type MOS transistor includes a bias voltage storage pole and a source voltage input pole connected to a voltage source.    An optical signal is output from an output terminal of the MOS transistor based on the potential of the electric charge accumulation pole which is charged using a charging switch. The reference voltage is added to the bias voltage storage pole in response to a charging control signal, using a signal reading switch. The light signal is output from the output terminal through the terminal connected to the output terminal, in response to a reading control signal.    USE -   In facsimile, camera.    ADVANTAGE -   Exhibits large operation range, and sensitivity. Compensates DC offset accompanied by temperature variation. Improves image signal reading rate.