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.

Abstract: A substrate forming a sensor element is connected to a non-inverting input terminal of an operational amplifier, and a common voltage is applied thereto from a reference voltage supply circuit to fix them to the same potential. Thus, the impedances of the non-inverting input terminal and of the inverting input terminal of the operational amplifier are matched with respect to the power source. Therefore, noise superposed on a power source line can be greatly decreased by noise-removing characteristics determined by CMRR characteristics of the operational amplifier. As a result, a capacitive-type acceleration sensor exhibits sensor characteristics of frequency noise suppressing effect.

Abstract: In a capacitance type semiconductor dynamic quantity sensor, a sensor chip and a circuit are connected to each other through adhesive film having an elasticity of 200 MPa or less to reduce the temperature characteristic. Four bonding wires for connecting the sensor chip and the circuit chip are arranged so that each of the bonding wires is located at the center portion of each side portion of the sensor chip or at each corner portion of the sensor chip, thereby sufficiently increasing the interval between the bonding wires and thus sufficiently reducing the absolute value of the parasitic capacitance thus occurring. Therefore, even when the parasitic capacitance between the four bonding wires is varied, the variation is very small, and thus the influence on the sensor characteristic can be reduced.

Abstract: An acceleration sensor system includes: a first and a second fixed electrodes; a movable electrode for providing a first and a second capacitors; a detection capacitor for detecting a capacitance difference between the first and the second capacitors; a charge voltage conversion circuit for converting a capacitance change of the detection capacitor to an output voltage; a detection bias voltage applying circuit; a vibrating circuit for vibrating the movable electrode such that a displacement bias voltage is applied in a first period and no displacement bias voltage is applied in a second period; a sampling circuit for sampling the output voltage during the second period when the movable electrode is constantly vibrated; and an acceleration signal generating and outputting circuit for generating an acceleration signal on the basis of a sampling result.

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.

Abstract: A substrate forming a sensor element is connected to a non-inverting input terminal of an operational amplifier, and a common voltage is applied thereto from a reference voltage supply circuit to fix them to the same potential. Thus, the impedances of the non-inverting input terminal and of the inverting input terminal of the operational amplifier are matched with respect to the power source. Therefore, noise superposed on a power source line can be greatly decreased by noise-removing characteristics determined by CMRR characteristics of the operational amplifier. As a result, a capacitive-type acceleration sensor exhibits sensor characteristics of frequency noise suppressing effect.

Abstract: In a capacitive physical quantity sensor, a C-V converter converts a variation in a capacitance between a movable electrode and a fixed electrode into a voltage to output the converted voltage in a first operating mode. The C-V converter also outputs a constant voltage in a second operating mode. An amplifier amplifies the converted voltage to output a first voltage, and amplifies the constant voltage to output a second voltage. A first sample and hold circuit operates in the first operating mode to sample and hold the first voltage. A second sample and hold circuit operates in the second operating mode to sample and hold the second voltage. A first differential amplifier obtains 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.

Abstract: In a capacitive physical quantity sensor, a C-V converter converts a variation in a capacitance between a movable electrode and a fixed electrode into a voltage to output the converted voltage in a first operating mode. The C-V converter also outputs a constant voltage in a second operating mode. An amplifier amplifies the converted voltage to output a first voltage, and amplifies the constant voltage to output a second voltage. A first sample and hold circuit operates in the first operating mode to sample and hold the first voltage. A second sample and hold circuit operates in the second operating mode to sample and hold the second voltage. A first differential amplifier obtains 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.

Abstract: In a capacitance type semiconductor dynamic quantity sensor, a sensor chip and a circuit are connected to each other through adhesive film having an elasticity of 200 MPa or less to reduce the temperature characteristic. Four bonding wires for connecting the sensor chip and the circuit chip are arranged so that each of the bonding wires is located at the center portion of each side portion of the sensor chip or at each corner portion of the sensor chip, thereby sufficiently increasing the interval between the bonding wires and thus sufficiently reducing the absolute value of the parasitic capacitance thus occurring. Therefore, even when the parasitic capacitance between the four bonding wires is varied, the variation is very small, and thus the influence on the sensor characteristic can be reduced.

Abstract: An acceleration sensor system includes: a first and a second fixed electrodes; a movable electrode for providing a first and a second capacitors; a detection capacitor for detecting a capacitance difference between the first and the second capacitors; a charge voltage conversion circuit for converting a capacitance change of the detection capacitor to an output voltage; a detection bias voltage applying means; a vibrating means for vibrating the movable electrode such that a displacement bias voltage is applied in a first period and no displacement bias voltage is applied in a second period; a sampling means for sampling the output voltage during the second period when the movable electrode is stationarily vibrated; and an acceleration signal generating and outputting means for generating an acceleration signal on the basis of a sampling result.