| 摘要 |
PURPOSE:To allow rise time and fall time to coincide with each other and to eliminate the distortion of a signal, by adding a circuit capable of controlling the base current of a phototransistor as the photodetection side of a photocoupler. CONSTITUTION:To the base of the phototransistor 32 of a photocoupler 3, a photodiode 39 coupled optically with a light emitting diode 38 is connected. When the current flowing through the light emitting diode 38 is varied through a resistance VR, the rise time and fall time of the phototransistor 32 vary and the current is varied in such a way that the rise time and fall time coincide with each other. When an input pulse PI is applied to a light emitting diode 31 through a resistance Rin, an output pulse having the same width with the input pulse PI and delayed by the rise time appears at the output of the photocoupler. |
