| 摘要 |
PROBLEM TO BE SOLVED: To reduce noise of an output signal utilizing a capacitive detection element such as a pyroelectric element.SOLUTION: An amplifier circuit 18 is a chopper type amplifier circuit generating an amplification signal SA corresponding to an electric charge supplied from a pyroelectric element. In an amplification period QA, a first input terminal NA1 is connected to a negative side input terminal TA1 of an operational amplifier 34, a second input terminal NA2 is connected to a positive side input terminal TA2, a first output terminal NB1 is connected to a positive side output terminal TB1, and a second output terminal NB2 is connected to a negative side output terminal TB2. In an amplification period QB, the first input terminal NA1 is connected to the positive side input terminal TA2, the second input terminal NA2 is connected to the negative side input terminal TA1, the first output terminal NB1 is connected to the negative side output terminal TB2, and the second output terminal NB2 is connected to the positive side output terminal TB1. In a period between the amplification period QA and the amplification period QB, an electric potential difference between the negative side input terminal TA1 and the positive side input terminal TA2 is reduced in a state of the first output terminal NB1 and the second output terminal NB2 being insulated from the operational amplifier 34.SELECTED DRAWING: Figure 4 |
