Abstract: A filter circuit includes a voltage amplifier, a resistor, a capacitor, and an analog switch connected between the voltage amplifier and the capacitor. When the voltage amplifier is turned on, the analog switch is opened so that the capacitor is disconnected from the voltage amplifier. Thus, an output voltage of the voltage amplifier sharply increases to its steady state value, as soon as the voltage amplifier is turned on. When the output voltage of the voltage amplifier is fully stabilized, the analog switch is closed so that the capacitor is connected to the voltage amplifier. During the period of time when the analog switch is closed, the filter circuit is configured as an imperfect integrator circuit with filter characteristics that depend on a capacitance of the capacitor and a resistance of the resistor.

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: A filter circuit includes a voltage amplifier, a resistor, a capacitor, and an analog switch connected between the voltage amplifier and the capacitor. When the voltage amplifier is turned on, the analog switch is opened so that the capacitor is disconnected from the voltage amplifier. Thus, an output voltage of the voltage amplifier sharply increases to its steady state value, as soon as the voltage amplifier is turned on. When the output voltage of the voltage amplifier is fully stabilized, the analog switch is closed so that the capacitor is connected to the voltage amplifier. During the period of time when the analog switch is closed, the filter circuit is configured as an imperfect integrator circuit with filter characteristics that depend on a capacitance of the capacitor and a resistance of the resistor.

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: A semiconductor sensor chip is provided with a weight portion supported in a frame via beams whereby acceleration up to substantially ±1 G can be detected by utilizing piezoresistance effect of resistor elements formed on the beams. The semiconductor sensor chip is supported by a seat having a thermal expansion coefficient equivalent to that of the semiconductor sensor chip via the frame. The frame and the seat are adhered to each other by a flexible adhesive agent mixed with a plurality of resin beads functioning as spacers and under an adhesion state, air damping of the weight portion is carried out by setting a dimension of an air gap between the weight portion and the seat to a range of 7 through 15 &mgr;m.

Abstract: An acceleration sensor is constructed by a substrate, a cylindrical dead-weight movable electrode to be displaced by acceleration, a fixed electrode from the inside of which a cylinder is hollowed, a cylindrical anchor arranged on the substrate for supporting the dead-weight movable electrode with elastic transformable structural material and beams. When acceleration is applied from the outside, the cylindrical detecting face of the dead-weight movable electrode and the cylindrical detected face of the fixed electrode are in contact on a two-dimensional plane parallel to the substrate and the acceleration sensor detects the contact. A radial interval between the detecting face of the dead-weight movable electrode and the detected face of the fixed electrode is set in view of the elastic modulus of the beams so that external force can be detected isotropically and the acceleration sensor detects acceleration on a two-dimensional plane nondirectionally.

Abstract: A knock sensor for which a fabrication process is simple and moreover which can detect up to a high-frequency region is provided. A sensing element 11 composed of a semiconductor the weight (mass) thereof being 1 g or less and a signal processing circuit 11 are mounted on a fixing pedestal 9. The fixing pedestal 9 is fixed to a connector 2 side by means of adhesive or the like. Additionally, the connector 2 is fixed by means of caulking 16 of a housing 1. As a result thereof, the sensing element 11 is disposed within a space formed by the fixing pedestal 9 and the housing 1.