| 摘要 |
PURPOSE:To execute an accurate light/voltage signal conversion operation by using first and second photodetectors including static induction transistors, detecting an input light by the first photodetector, setting the second photodetector to a shielding state, and differentially amplifying detection signals from the first and second photodetectors. CONSTITUTION:A detecting current corresponding to input optical information is obtained from a first photodetector 11, and a voltage signal is output from a first current/voltage conversion circuit 13. A second photodetector 12 is, on the other hand, shielded, a dark current corresponding to the state of a zero input light is supplied to a second voltage/current conversion circuit 14, which generates a voltage signal corresponding the dark current as a reference voltage signal. Since the output voltage signals from the conversion circuits 13, 14 are supplied to a differential amplifier circuit 15, a GB product can be enhanced in accuracy in the order of approx. hundred times as compared with the case that the output signal from an optical element is amplified and output by a conventional phototransistor, photodiode, etc. |
