Capacitive physical quantity sensor
First Claim
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1. A capacitive physical quantity sensor comprising:
- a sensor element including a movable electrode displaceable in accordance with a variation of a physical quantity, and first and second fixed electrodes facing the movable electrode, wherein a first periodic carrier wave voltage is applied to the first fixed electrode and a second periodic carrier wave voltage is applied to the second fixed electrode, the first and second periodic carrier wave voltages are inverse to each other; and
a detecting circuit including a capacitance-voltage conversion circuit, into which an input potential corresponding to a variation of a capacitance between the movable electrode and the first and second fixed electrodes is input, and from which a voltage signal corresponding to the variation of the capacitance is output, whereinthe detecting circuit further includes a sample-hold circuit for sampling and holding the voltage signal,the sample-hold circuit includes a switch for switching the sampling and the holding,the switch includes a P-channel MOS transistor and a N-channel MOS transistor, which are connected in parallel to each other, andthe P-channel MOS transistor and the N-channel MOS transistor have a back gate potential, which is approximately equal to an average voltage of the first periodic carrier wave voltage and the second periodic carrier wave voltage.
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Abstract
A capacitive physical quantity sensor includes a sensor element and a detecting element. The sensor element includes first and second fixed electrodes facing a movable electrode. A first voltage is applied to the first fixed electrode and a second voltage is applied to the second fixed electrode. The detecting circuit includes a capacitance-voltage conversion circuit, in which an operational amplifier, a capacitor and a switch including a P-channel MOS transistor and a N-channel MOS transistor are disposed. The transistors have a back gate potential, which is approximately equal to an average voltage of the first voltage and the second voltage.
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6 Claims
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1. A capacitive physical quantity sensor comprising:
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a sensor element including a movable electrode displaceable in accordance with a variation of a physical quantity, and first and second fixed electrodes facing the movable electrode, wherein a first periodic carrier wave voltage is applied to the first fixed electrode and a second periodic carrier wave voltage is applied to the second fixed electrode, the first and second periodic carrier wave voltages are inverse to each other; and a detecting circuit including a capacitance-voltage conversion circuit, into which an input potential corresponding to a variation of a capacitance between the movable electrode and the first and second fixed electrodes is input, and from which a voltage signal corresponding to the variation of the capacitance is output, wherein the detecting circuit further includes a sample-hold circuit for sampling and holding the voltage signal, the sample-hold circuit includes a switch for switching the sampling and the holding, the switch includes a P-channel MOS transistor and a N-channel MOS transistor, which are connected in parallel to each other, and the P-channel MOS transistor and the N-channel MOS transistor have a back gate potential, which is approximately equal to an average voltage of the first periodic carrier wave voltage and the second periodic carrier wave voltage. - View Dependent Claims (2, 3, 4, 5, 6)
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Specification