| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an illuminance sensor in which the current consumption does not depend on the illuminance of incident light. <P>SOLUTION: Amplifiers 21 to 24 and a subtraction circuit 25 are driven by a constant-current source (not shown). The subtraction circuit 25 outputs a difference voltage between output voltages of a photo detector 15 and a photo detector 16. A sample hold circuit 30 samples or holds a voltage of the other end of a capacitor 13 based on the difference voltage. The voltage of the other end of the capacitor 13 is fixed to a reference voltage by turing on a switch 28 when the output voltage of the subtraction circuit 25 start changing. <P>COPYRIGHT: (C)2012,JPO&INPIT |
