Patent ID: 8723097

Claim:
An illuminance sensor of a voltage output type, comprising: a first photodetector element for outputting a photovoltage based on incident light; a second photodetector element; a subtraction circuit that is driven by a constant current source, for outputting a differential voltage between an output voltage of the first photodetector element and an output voltage of the second photodetector element; a sample/hold circuit; a capacitor having a first electrode coupled to an output terminal of the subtraction circuit and a second electrode coupled to an input terminal of the sample/hold circuit; and a switch provided between a node to which a reference voltage is supplied and the second electrode of the capacitor, the sample/hold circuit performing one of sampling and holding of a voltage at the second electrode of the capacitor based on the differential voltage, wherein a consumption current of the illuminance sensor is substantially independent of an illuminance level of the incident light.