Patent ID: 7312450

Claim:
An infrared detecting device, comprising: a pyroelectric element which generates a current signal based on incoming infrared radiation; an I/V conversion circuit which converts said current signal into a voltage signal; a voltage amplification circuit which selectively amplifies components with prescribed frequencies of said voltage signal to issue a components-amplified voltage; a detection circuit which provides a comparison between the components-amplified voltage and a prescribed detection threshold voltage to issue a detection signal of the infrared radiation; an output circuit which issues an output signal based on the detection signal; and a drive power supply circuit which supplies a drive current to each of signal circuits comprised of the I/V conversion circuit, the voltage amplification circuit, the detection circuit and the output circuit; wherein said drive power supply circuit is comprised of: a current generating circuit which includes a reference current source, a fixed current source and a variable current source, said reference current source being configured to generate a reference current, said fixed current source being configured to provide a fixed current based on said reference current, said variable current source being configured to provide a variable current varying with said reference current; and a distribution circuit configured to distribute the drive current to a part of said signal circuits based on the current from said fixed current source, said distribution circuit being configured to distribute the drive current to the remaining part of said signal circuits based on the current from said variable current source; the part of said signal circuits including at least said I/V conversion circuit.