| 摘要 |
The present invention aims to avoid mutual interference of outputs of passive infrared detectors in an amplifier circuit of an infrared sensor to be amplified by a single system of amplifier circuit by cyclically switching outputs from a plurality of passive infrared detectors at a predetermined cycle. P1 and P2 each represents a passive infrared detector, and switches 21 and 22 can be switched over cyclically. Between an operational amplifier 12 and an operational amplifier 13, series circuits of capacitors and switches are provided in parallel as many as the passive infrared detectors. Switches 201 and 202 are opened and closed in synchronization with the switches 21 and 22 respectively. The capacitor C30 is used when an output from the passive infrared detector P1 is amplified, and a capacitor C31 is used when an output from the passive infrared detector P2 is amplified. Thus, it is possible to avoid the interference of the outputs of the passive infrared detectors P1 and P2 with each other. |
