PURPOSE: To make pulse response speed higher than conventional speed by suppressing charge storage between a collector and a base.

CONSTITUTION: This photocoupler suppresses the charge storage between the collector and the base by providing a light emitting diode 2 to emit light while responding to an input electric signal, photodiode 3 to generate a current while responding to this light emission, transistor 4 to obtain the amplified current at the emitter and the collector while connecting the base to one terminal of the photodiode 3, and Schottky barrier diode 5 for speed-up which is connected between the collector and the base of the transistor 4.