Patent ID: 8080857

Claim:
An illuminance sensor, comprising: a semiconductor photodetecting device formed within a P-type semiconductor substrate, the semiconductor photodetecting device including: a P-type well region and an N-type well region provided side by side along a surface of the P-type semiconductor substrate; a high-concentration N-type region formed in the neighborhood of a surface of the P-type well region; and a high-concentration P-type region formed in the neighborhood of a surface of the N-type well region; and an arithmetic circuit for extracting a first photoelectric current which flows through a PN junction formed by the P-type well region and the high-concentration N-type region and a second photoelectric current obtained by adding a photoelectric current which flows through a PN junction formed by the N-type well region and the P-type semiconductor substrate to a photoelectric current which flows through a PN junction formed by the N-type well region and the high-concentration P-type region, and providing a current obtained by performing predetermined arithmetic processing on the first and second photoelectric currents, as a detected output.