Photointerrupter driving circuit capable of decreasing the number of parts

摘要

In a photointerrupter comprising a light emitting diode and a photo transistor which are opposed to each other, the photo transistor has an emitter which is grounded through a resistor while the light emitting diode has a cathode which is connected to an input terminal of a one IC chip for controlling a flexible disk drive. The one IC chip incorporates a constant current source which is connected to the input terminal through an npn-type bipolar transistor. The one IC chip incorporates a logic circuit having an output terminal which is connected to a base of the npn-type bipolar transistor.