Patent ID: 7434466

Claim:
An electrostatically-driven/capacitance-detection type gyro sensor comprising: a sensing element including a movable part displaceable in a motion plane, a first electrode provided in said movable part and applied with a bias voltage; a second electrode applied with a drive signal to generate an electrostatic force acting on said movable part in order that said movable part vibrates along a first direction on said motion plane, a third electrode forming a first variable capacitor with said movable part, a capacitance of said first variable capacitor varying in accordance with a displacement of said movable part along said first direction, and a fourth electrode forming a second variable capacitor with said movable part, a capacitance of said second variable capacitor varying in accordance with a displacement of said movable part along a second direction on said motion plane, said second direction being orthogonal to said first direction; a reference voltage generator generating, from a power supply voltage supplied from outside said gyro sensor, a reference voltage which is constant irrespective of variation of said power supply voltage; a bias voltage generator generating said bias voltage by amplifying said reference voltage; a capacitance-voltage converter converting said capacitance of said first variable capacitor into a first voltage signal whose voltage level varies following variation of said capacitance of said first variable capacitor, the first voltage signal having a first offset voltage proportional to the reference voltage, and converting said capacitance of said second variable capacitor into a second voltage signal whose voltage level varies following variation of said capacitance of said second variable capacitor, the second voltage signal having a second offset voltage proportional to the reference voltage; a drive signal generator generating said drive signal by amplifying and phase-adjusting said first voltage signal, said drive signal having an offset voltage proportional to said reference voltage; and a sensor output signal generator generating, from said second voltage signal, a sensor output signal having a magnitude corresponding to said voltage level of said second voltage signal, said sensor output signal having an offset voltage proportional to said power supply voltage.