| 摘要 |
An optical sensor circuit of the invention includes a photodiode, a reset switch, a capacitor for charge integration, an operational amplifier, reference voltage generating circuits connected to the operational amplifier via switches, and a reference voltage selecting circuit connected to the control input terminals of the respective switches. The reference voltage for defining the upper limit of the output range of the optical sensor circuit can be set at an appropriate value. Since the reference voltage is set at an appropriate value corresponding to the input range of an A/D converter due to this circuit configuration, a conversion error in the A/D converter is avoided, and the analog output of the optical sensor circuit is converted to a digital quantity while the resolution of the A/D converter is fully utilized.
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