Signal processing circuit

摘要

In an integration mode, since a switch becomes OFF, a positive feedback path from an output terminal of an operational amplifier to a positive input terminal is blocked. Therefore, oscillation can be prevented even when a voltage of a signal line connected to a reference voltage supply point varies due to an impedance of the reference voltage supply point not being 0. In the integration mode, a resistor and a capacitor function as a noise filter. Further, in a reset mode, a switch becomes ON, and charge is accumulated in the capacitor depending on a reference voltage of the reference voltage supply point.

主权项

1. A signal processing circuit comprising:
an integration circuit configured to receive a charge signal corresponding to a charge accumulated in a capacitor to be measured, integrate the charge signal, and convert the charge signal into a voltage signal; and a voltage supply circuit configured to supply a reference voltage to the integration circuit, wherein the integration circuit includes:
an operational amplifier having a negative input terminal that receives the charge signal, a positive input terminal that receives the reference voltage, and an output terminal;a positive feedback path from the output terminal to the positive input terminal of the operational amplifier;a first negative feedback path from the output terminal to the negative input terminal of the operational amplifier;a second negative feedback path from the output terminal to the negative input terminal of the operational amplifier, the second negative feedback path being in parallel with the first negative feedback path;a first capacitor provided on the first negative feedback path; anda first switch provided on the second negative feedback path, and wherein the voltage supply circuit includes:
a second capacitor connected to the positive input terminal of the operational amplifier, the second capacitor holding the reference voltage;a second switch provided on the positive feedback, the second switch becoming OFF when the first switch is OFF, and becoming ON when the first switch is ON; anda reference voltage supply point provided on the positive feedback path, the reference voltage supply point supplying the reference voltage to the second capacitor via the second switch.