REFLECTION TYPE PHOTOELECTRIC SWITCH

摘要

PURPOSE:To obtain the constitution of a reference voltage generating circuit suitable to IC-implementation by connecting the output terminal of a current mirror circuit to the reference input terminal of a comparing circuit and connecting a transistor (TR) for reference voltage switching to part of an output-side load resistance is parallel. CONSTITUTION:A circuit which compares the difference signal between both outputs of position detection type photodetectors 4a and 4b with a reference voltage for distance setting is provided, and the reference voltage generation part constituted by connecting the output terminal of the current mirror circuit M1 where a variable resistor VR1 for reference voltage setting is connected to the input side through a resistance-current converting circuit CT1 to the reference input terminal of the comparing circuit and also connecting the TR Q4 for reference voltage switching to part of the output-side load resistance in parallel is provided. Then, the reference voltage is switched automatically simultaneously with the detection of a body to lower a return photodetection level and thus provide detection sensitivity hysteresis, and the input current of the current mirror circuit M1 is adjusted by a variable resistor Rd for detection distance setting to prevent the setting or variation of the hysteresis width from exerting influence upon the detection reference voltage.