| 摘要 |
PURPOSE:To reduce discharging time constant of charge stored in an LED and to decrease the falling time of an optical output waveform by providing four driving circuits respectively connected to the anode and cathode of a light emitting diode, and to the anode and cathode of a diode. CONSTITUTION:Electric pulse signals S1, S2 are 'H' level, driving circuits 2 (TR1), 5 (TR2) are turned ON, driving circuits 9 (TR3), 12 (TR4) are turned OFF, a current determined by a constant current source 7 is all fed to an LED 1 side, and the LED 1 emits light. Then, when the signals S1, S2 are 'L' level, the current of the source 7 is all fed to a diode 11, and the LED 1 is turned off. In this case, since the output of the circuit 2, i.e., the emitter of the transistor TR1 is the 'L' level and the output of the circuit 9, i.e., the emitter of the transistor TR3 is the 'H' level, the charge stored in the LED 1 is rapidly discharged through the diode 11, thereby shortening the falling time of an optical output waveform. |
