| 摘要 |
PURPOSE:To obtain a light receiving circuit which is not influenced by a dark current, an offset, etc., by differentiating an electric signal corresponding to optical intensity, and comparing this signal with a reference voltage to which hysteresis is applied in advance. CONSTITUTION:A photocurrent from a photodetector 1 is converted to a voltage value 2 by a current/voltage converting part 2. This voltage value is converted to a differential signal once by a differentiating circuit 3, and subsequently, the mean value of the differential signal is derived by a smoothing circuit 4. Next, the differential signal is compared with a reference voltage Vc, but the differential signal is converted quickly to the mean value, therefore, when the reference voltage Vc is used as the mean value, two inputs of a comparator go to the same voltage, and a malfunction is generated. Therefore, hysteresis of positive and negative is supplied to the reference voltage Vc, a malfunction is prevented, and the same waveform as the original signal is restored. |
