Patent ID: 7456731

Claim:
A capacitive-type physical quantity sensor comprising: first and second substrates provided separately; a sensor element formed on the first substrate and having moving electrodes and first and second fixed electrodes, the moving electrodes undergoing a displacement depending upon a change in physical quantity, and the first and second fixed electrodes being arranged to face the moving electrodes and receive periodic carrier waves having phases opposite to each other; and a detector circuit formed on the second substrate and including a C-V conversion circuit that receives a signal that varies depending upon a change in a capacitance formed between the moving electrodes and the first and second fixed electrodes, the detector circuit producing a voltage that varies depending upon a change in the capacitance, wherein the C-V conversion circuit includes an operational amplifier and a reference voltage supply circuit, the operational amplifier having a first input terminal to receive a signal that varies depending upon a change in the capacitance and a second input terminal to receive a reference voltage of the reference voltage supply circuit, and wherein the first substrate is electrically connected to the second input terminal of the operational amplifier so that the voltage of the first substrate is fixed to the reference voltage of the reference voltage supply circuit.