Patent ID: 7291825

Claim:
A capacitance type physical quantity sensor comprising: a sensing part including a capacitor element whose capacitance varies depending on a physical quantity to be sensed, said sensing part generating a capacitance signal representing a magnitude of said capacitance of said capacitor element; and a sensor circuit including a charge amplifier converting said capacitance signal into a voltage signal; wherein said charge amplifier includes an operational amplifier applied with said capacitance signal at an inverting input terminal thereof and applied with a reference voltage at a non-inverting input terminal thereof, a first capacitor connected between said inverting input terminal and an output terminal of said operational amplifier, a feedback resistor connected in parallel to said first capacitor, and a switch connected in parallel to said first capacitor and configured to be closed to make a short circuit between said inverting input terminal and said output terminal upon receiving a refresh signal supplied from outside of said capacitance type physical quantity sensor.