| 摘要 |
PROBLEM TO BE SOLVED: To provide a smoke sensor for simplifying and omitting a means for preventing disturbance light from being incident on a light-receiving unit. SOLUTION: A current-voltage converting circuit 2 is provided with: a second feedback circuit 5 which outputs an output voltage Vout according to the magnitude of a low-frequency component at or lower than a predetermined second cut-off frequency; and a correcting transistor Q1 which supplies a correction current Ic2 according to the magnitude of the output of the second feedback circuit 5 through a connection terminal Tin of a conversion unit 3 to a photo-diode PD. The second feedback circuit 5 comprises a second integration circuit 9 which integrates the output voltage Vout of the conversion unit 3; and a sample-and-hold circuit 10 which samples and holds the output of the second integration circuit 9 in a sensing period, during which a pulsed detection signal is input. COPYRIGHT: (C)2010,JPO&INPIT
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