Patent ID: 7441458

Claim:
A system of measuring a physical quantity based on a detection signal using a vibrator, a self-oscillating circuit oscillating a driving vibration in said vibrator and a detection circuit for outputting a detection signal from said vibrator, wherein said self-oscillating circuit comprises a current/voltage converter that converts an alternating current to a voltage, and a low pass filter comprising a resistance and a condenser, said low pass filter having an amplification factor having a proportionality factor of 0.9 or larger and 1.1 or smaller with respect to (1/R 1 ·C 1 ), C 1 representing a capacitance of said condenser of said low pass filter and R 1 representing a resistance value of said resistance of said low pass filter; wherein said detection circuit comprises a charge amplifier circuit amplifying an output signal from said vibrator; and wherein said current-voltage converter and said charge amplifier circuit are formed in a monolithic IC.