| 摘要 |
PROBLEM TO BE SOLVED: To detect a change in ambient illuminance in a wide range while eliminating an influence of switching noise and the on resistance of a switch, by changing a detection range without inserting a switch in an analog signal line in a photodetection circuit for detecting the brightness of outdoor daylight. SOLUTION: This photodetection circuit comprises a photoelectric conversion element 11, a first amplifying means 12-13 for adding a voltage proportional to a detected current output from the photoelectric conversion element to a reference voltage and outputting it, and a second amplifying means 21-25 which generates a detection voltage by amplifying the difference between the voltage output from the first amplifying means and the reference voltage with a first amplification factor and adding it to the reference voltage, when a control voltage is in a first state, and generates a detection voltage by amplifying the difference between the voltage output from the first amplifying means and the reference voltage with a second amplification factor and adding it to the reference voltage, when the control signal is in a second state. COPYRIGHT: (C)2006,JPO&NCIPI
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