Patent ID: 7109727

Claim:
A capacitive physical quantity sensor comprising: a sensor element having a movable electrode and a fixed electrode opposite to the movable electrode, the movable electrode being displacable depending on change of a physical quantity; a C-V converter configured to convert a variation in a capacitance between the movable electrode and the fixed electrode into a voltage to output the converted voltage in a first operating mode, the C-V converter being configured to output a constant voltage in a second operating mode; an amplifier connected to the C-V converter and configured to amplify the converted voltage to output an amplified first voltage, the amplifier being configured to amplify the constant voltage to output an amplified second voltage; a first sample and hold circuit connected to the amplifier and configured to operate in the first operating mode to sample and hold the first voltage outputted from the amplifier; a second sample and hold circuit connected to the amplifier and configured to operate in the second operating mode to sample and hold the second voltage outputted from the amplifier; and a first differential amplifier connected to the first and second sample and hold circuits and configured to obtain a difference voltage between the first voltage held by the first sample and hold circuit and the second voltage held by the second sample and hold circuit.