Patent ID: 7000471

Claim:
An angular velocity sensor device comprising: an angular velocity sensor including an oxide film affixed to a first semiconductor layer and a second semiconductor layer disposed above the first semiconductor layer, wherein the angular velocity sensor further includes a weight part formed within the second semiconductor layer that oscillates in a first direction and a second direction perpendicular to this first direction, a pair of driving electrodes for applying driving voltages for oscillating the weight part in the first direction, a pair of monitor electrodes for monitoring the oscillation of the weight part in the first direction, and detection electrodes for detecting oscillation of the weight part in the second direction occurring when, on top of the oscillation in the first direction, an angular velocity acts about an axis orthogonal to the first and second directions; a self-oscillating circuit for generating first and second driving voltages mutually opposite in phase to be applied to the pair of driving electrodes; a pair of C/V-converting circuits for impressing a predetermined DC voltage on capacitors formed by the monitor electrodes and the weight part and detecting currents that consequently flow and generating voltages proportional to a static capacitances of the capacitors; a differential amplifier circuit for obtaining a voltage difference between the output voltages of the C/V-converting circuits and supplying the voltage difference to the self-oscillating circuit as a feedback voltage; a switch for selecting the first or second driving signals; and an adding circuit for adjusting the amplitude of the driving signal selected with the switch and adding the driving signal selected to the voltage difference outputted by the differential amplifier circuit, wherein an output signal of the adding circuit is supplied to the self-oscillating circuit as a feedback signal.