| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a signal readout circuit capable of improving an S/N ratio at low cost. <P>SOLUTION: The signal readout circuit includes: a selection switching device Q<SB>S</SB>to select whether the output of a thermopile 1 is read out; an integrator 4 with the inverting input terminal of an operational amplifier OP connected in series to the selection switching device Q<SB>S</SB>through a first capacitor C<SB>1</SB>, with a non-inverting input terminal connected to a virtual ground, with a parallel circuit of a second capacitor C<SB>2</SB>and a first reset switching device Q<SB>R</SB>connected between the non-inverting and the inverting input terminals, and with a second reset switching device Q<SB>R1</SB>connected between the virtual ground and a connecting point of the selection switching device Q<SB>S</SB>and the first capacitor C<SB>1</SB>; and a hold capacitor C<SB>LS</SB>connected between the output terminal and the virtual ground of the integrator 4 through a sampling switching device Q<SB>SS</SB>. The transconductance of the operational amplifier OP is set to the minimal value of the transconductance satisfying the sampling period of time. <P>COPYRIGHT: (C)2009,JPO&INPIT |
