JP2000131072A - Capacity change detection circuit device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect the capacity change in a pair of capacitors being connected in series with a simple circuit configuration. SOLUTION: A rectangular wave signal generation circuit 30 applies a rectangular wave signal S1 across a pair of capacitors Ca and Cb that are connected in series and takes out a signal where a rectangular wave signal S1 is amplitude-modulated by a signal for indicating the capacity change as a voltage signal S2 via a charge amplifier 50 from the connection point between the capacitors Ca and Cb along with the capacity change in the capacitors Ca and Cb. The voltage signal S2 is supplied to first and second sample/hold circuits 60 and 70, and the first and second sample/hold circuits 60 and 70 sample and hold the signal S2 by first and second pulse train signals S3 and S4 that have the same cycle as the rectangular wave signal S1 from a pulse train signal generation circuit 40 and are in opposite phases each other and then output it to an operation circuit 80. The operation circuit 80 synthesizes each signal being sampled and held in the above before outputting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to an angular velocity sensor, an acceleration sensor, and the like, applies a voltage signal to both ends of a pair of capacitors connected in series, and extracts a voltage signal extracted from a connection point between the same pair of capacitors. And a capacitance change detection circuit device that detects a change in the capacitance of the same pair of capacitors based on

[0002]

2. Description of the Related Art Conventionally, this type of apparatus is disclosed in, for example,
As disclosed in Japanese Patent Application Laid-Open No. 0-122869, a sine-wave high-frequency signal is applied to both ends of a pair of capacitors connected in series, and the high-frequency signal (corresponding to a carrier signal) is converted into a signal representing a change in capacitance of the capacitor (corresponding to a carrier signal). A signal modulated by the modulated wave signal) is extracted from a connection point between the pair of capacitors, and the extracted signal is demodulated to extract a signal indicating a change in capacitance of the pair of capacitors.

[0003]

However, in the above-mentioned conventional apparatus, a demodulation circuit for demodulating a modulated signal becomes complicated, and the demodulation circuit is provided with a low-pass filter or a band-pass filter. However, there is a problem that a circuit for extracting a signal indicating a change in the capacitance of the pair of capacitors becomes complicated.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to provide a capacitance change detecting circuit device capable of extracting a signal indicating a capacitance change of a pair of capacitors with a simple configuration. Is to provide.

In order to achieve the above object, a feature of the present invention is that a voltage signal is applied to both ends of a pair of capacitors connected in series and the same signal is applied based on a voltage signal extracted from a connection point between the same pair of capacitors. In a capacitance change detection circuit device for detecting a change in capacitance of a pair of capacitors, a rectangular wave signal generation circuit for generating a rectangular wave signal and applying the same rectangular wave signal to both ends of the pair of capacitors, and a period of the rectangular wave signal A pulse train signal generating circuit for generating a pulse train signal having a period that is an integral multiple of the pulse train signal, and a sample and hold circuit for sampling and holding a voltage signal extracted from the connection point with the pulse train signal.

According to this, when the capacitance of a pair of capacitors changes, a voltage signal obtained by amplitude-modulating a rectangular wave signal according to a change in the capacitance of the capacitor, that is, a rectangular wave signal Is amplitude-modulated by a signal representing a change in the capacitance of the capacitor. Then, this voltage signal is sampled by a pulse train signal having a period that is an integral multiple of the period of the rectangular wave signal and is held by the sample-and-hold circuit, so that a signal representing a change in the capacitance of the capacitor is extracted from the sample-and-hold circuit. Will be. In this case, since the rectangular wave signal is applied to the pair of capacitors, the sample-and-hold circuit does not require strict control of the sampling timing in the sample-and-hold circuit as compared with the case where the sine wave signal is applied to the pair of capacitors. It is possible to sample a signal that accurately represents a change in the capacitance of the capacitor. Further, since the sample and hold circuit also functions as a low-pass filter, no special low-pass filter is required. As a result, according to the feature of the present invention, it is possible to detect the change in the capacitance of the pair of capacitors with a simple circuit configuration, and to omit the low-pass filter to eliminate the phase of the output signal indicating the change in the capacitance of the capacitor. There is no need to consider delays.

Another feature of the present invention is that the sample and hold of the pulse train signal output from the pulse train signal generation circuit is controlled at a timing excluding a predetermined period immediately after the level change of the rectangular wave signal. It is in. According to this, the sample-and-hold circuit samples and holds the signal indicating the change in the capacitance of the capacitor without being affected by a transient change in the potential at the connection point between the pair of capacitors immediately after the level change of the rectangular wave signal. At the same time, the sampled and held signal can be output, and the change in the capacitance of the capacitor can be accurately detected.

Another feature of the present invention is that the pulse train signal generating circuit has a period which is an integral multiple of the period of the rectangular wave signal and which corresponds to the high level and the low level of the rectangular wave signal, respectively. And the first and second sample and hold circuits are configured to sample and hold the voltage signal extracted from the connection point with the first and second pulse train signals, respectively, and And an arithmetic circuit for synthesizing each output of the second sample and hold circuit to extract a signal representing a change in the capacitance of the pair of capacitors. According to this, the first and second sample-and-hold circuits sequentially sample and hold the voltage signal at the connection point between the pair of capacitors while dividing the rectangular wave signal into a high level and a low level. The outputs of the first and second sample-and-hold circuits are combined and operated by the operation circuit and output as a signal indicating a change in the capacitance of the capacitor, so that unnecessary noise is applied to the voltage signal at the connection point between the pair of capacitors. Even if a component is included, the noise component is canceled, and the change in the capacitance of the capacitor can be accurately detected.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows an angular velocity detecting device to which a capacitance change detecting circuit device according to the present invention is applied.

In this angular velocity detecting device, the vibrator is vibrated in the X-axis direction (the left-right direction in FIG. 1), and is rotated around the Z-axis (FIG. 1).
When the angular velocity acts around the direction perpendicular to the plane of the drawing), the angular velocity is detected by utilizing the fact that the vibrator vibrates in the Y-axis direction (vertical direction in FIG. 1) with an amplitude proportional to the angular velocity due to Coriolis force. A semiconductor element A incorporating the same vibrator, a driving circuit B connected to the semiconductor element A for driving the vibrator in the X-axis direction, and a driving circuit B for detecting vibration in the Y-axis direction of the vibrator as a capacitance change. And a capacitance change detection circuit according to the present invention.

First, the semiconductor element A will be described. The semiconductor element 10 has a square-shaped vibrator 11 provided on a central portion of a square-shaped substrate 10 by a predetermined distance. The vibrator 11 includes an anchor 12 a fixed on the substrate 10.
1 to 12d which are connected to the outer end at the outer end and are provided at a predetermined distance from the substrate 10 like the vibrator 11.
3a to 13d support the substrate 10 so as to be displaceable in the X-axis direction and the Y-axis direction in a horizontal plane.

A substrate 1 is provided on each outer side of the vibrator 11 in the X-axis direction.
A plurality of electrode fingers 14a and 14b are provided, each of which is fixed on the electrode 0, and each of the electrode fingers 14a and 14b extends in the X-axis direction and is arranged at equal intervals in the Y-axis direction. It has. Further, each of the comb-tooth electrodes 14a, 14
b, pad portions 15a and 15b fixed on the substrate 10 and connected to the comb-shaped electrodes 14a and 14b are provided on the outer sides in the X-axis direction, respectively.
Electrode pads 16a and 16b formed in a rectangular shape with a conductive metal (for example, aluminum) are provided on a and 15b, respectively.

A vibrator 1 is provided on the side of the vibrator 11 in the X-axis direction.
Like the first embodiment, comb-shaped electrodes 17a and 17b are provided, each of which is floating above the substrate 10 by a predetermined distance and formed integrally with the vibrator 11. Each of the comb-shaped electrodes 17a and 17b includes a plurality of electrode fingers extending outward in the X-axis direction and arranged at equal intervals in the Y-axis direction. 14b invades the center position in the width direction (Y-axis direction) between the electrode fingers. The comb-shaped electrodes 14a and 14b constitute a drive unit for the vibrator 11 together with the comb-shaped electrodes 17a and 17b.
1 is excited in the X-axis direction by electrostatic attraction when a drive signal is applied to the comb-like electrodes 14a and 14b.

A substrate 1 is provided on each outer side of the vibrator 11 in the Y-axis direction.
A plurality of sets of comb-teeth electrodes 21a, 21b are provided, each of which is fixed on a respective one of the comb-teeth sets 21a, 21b.
Has a plurality of electrode fingers extending in the X-axis direction and arranged at equal intervals in the Y-axis direction. The substrate 10 is provided on each outer side of the comb-teeth-shaped electrode sets 21a and 21b in the Y-axis direction.
And a comb-shaped electrode set 21a, 21b
Are provided on the pad portions 22a and 22b, respectively. On the pad portions 22a and 22b, electrode pads 23 formed of a conductive metal (for example, aluminum) in a square shape are provided.
a and 23b are provided respectively.

A vibrator 1 is provided on the side of the vibrator 11 in the Y-axis direction.
1, a plurality of comb-teeth-shaped electrode sets 24 which are floated from the substrate 10 by a predetermined distance and formed integrally with the vibrator 11
a and 24b are provided. Comb electrode set 2
Reference numerals 4a and 24b each include a plurality of electrode fingers extending in the X-axis direction and arranged at equal intervals in the Y-axis direction. Each of these electrode fingers is a respective one of the electrodes of the comb-like electrode sets 21a and 21b. Invading between fingers. However, the comb electrode set 24
Each of the electrode fingers a is displaced from the center position in the width direction between the electrode fingers of the comb-shaped electrode set 21a, and the respective electrode fingers are arranged outside the electrode fingers of the comb-shaped electrode set 21a in the Y-axis direction. The capacitors are close to each other, and each electrode finger close to each other forms a capacitor. Also, each of the electrode fingers of the comb-shaped electrode set 24b is also shifted from the center position in the width direction between the electrode fingers of the comb-tooth electrode set 21b, and the outer side in the Y-axis direction of each of the electrode fingers of the comb-shaped electrode set 21b. , The respective electrode fingers are close to each other, and the electrode fingers that are close to each other constitute a capacitor.

The comb-teeth-shaped electrode sets 21a and 21b together with the comb-teeth-shaped electrode sets 24a and 24b constitute a detection unit for the vibration of the vibrator 11. When the vibrator 11 vibrates in the Y-axis direction, the comb-teeth electrode sets 21a and 21b The distance between each pair of adjacent electrode fingers of the comb-shaped electrode sets 21a and 24a and the distance between each pair of adjacent electrode fingers of the comb-shaped electrode sets 21b and 24b are determined when one of the distances increases. They increase and decrease in opposite directions so that the other distance decreases. When the total capacity of a capacitor (hereinafter, referred to as a capacitor Ca) formed by each electrode finger of the comb-teeth electrode set 21a and the comb-teeth electrode set 24a increases (or), the comb-teeth electrode set 21b and the comb-teeth electrode The total capacity of a capacitor (hereinafter, referred to as a capacitor Cb) formed by each electrode finger of the set 24b decreases (or increases).

On the substrate 10, pad portions 25 fixed to the substrate 10 and connected to the anchors 12c are provided.
And an electrode pad 26 formed of a conductive metal (for example, aluminum) in a square shape is provided on the pad portion 25.

A method for manufacturing the semiconductor element A having such a configuration will be briefly described. First, an SO layer in which an upper layer made of a single-crystal silicon layer is provided on an upper surface of a lower layer made of a single-crystal silicon layer via an intermediate layer made of a silicon oxide film
An I (Silicon-On-Insulator) substrate is prepared, and the upper layer is doped with an impurity such as phosphorus or boron to lower the resistance of the upper layer. Next, the vibrator 11, anchors 12a to 12d, beams 13a to 13d, comb-shaped electrodes 14a, 14b, 17a,
17b, comb-shaped electrode sets 21a, 21b, 24a, 24b
And masking the upper surface of the upper portion corresponding to the pad portions 15a, 15b, 22a, 22b, 25 with a resist film,
The upper layer and the intermediate layer other than the above portions are removed by etching with reactive ion etching or the like. Thereby, the anchors 12a to 12d, the comb-shaped electrodes 14a and 14b, the comb-shaped electrode sets 21a and 21b, and the pad portions 15a, 15b, 22a, 22b and 25 fixed on the substrate 10 are formed.

Next, the vibrator 11, beams 13a to 13d, comb-like electrodes 17a and 17b, and comb-like electrode sets 24a and 24
The portion of the intermediate layer corresponding to b is removed by etching with a hydrofluoric acid aqueous solution or the like, and the vibrator 11, the beams 13a to 13d, the comb-shaped electrodes 17a, 17b, and the comb floating above the substrate 10 by a predetermined distance. Toothed electrode set 24a, 24b
To form Thereafter, the pad portions 15a, 15b, 22
a, 22b and 25 on the electrode pads 16a, 16b and 2
3a, 23b and 26 are formed. In the semiconductor element A thus configured, since the upper layer has a low resistance as described above, the vibrator 11, the anchors 12a to 12
d, the beams 13a to 13d, the comb-shaped electrodes 17a and 17b, the comb-shaped electrode sets 24a and 24b, the pad portion 25, and the electrode pad 26 are electrically connected in a state close to a conductor. Moreover, between the comb-shaped electrode 14a, the pad portion 15a and the electrode pad 16a, between the comb-shaped electrode 14b, the pad portion 15b and the electrode pad 16b, between the comb-shaped electrode set 21a, between the pad portion 22a and the electrode pad 23a, Electrode set 21b,
The pad portion 22b and the electrode pad 23b are also electrically connected to each other in a state close to a conductor.

The driving circuit B includes electrode pads 16a, 16b
To vibrate the vibrator 11 at a predetermined frequency f substantially equal to its resonance frequency (for example, about 10 KHz) with a constant amplitude in the X-axis direction.
Driving signals having a predetermined frequency f therebetween and having phases opposite to each other are applied. The capacitance change detection circuit C is shown in FIGS.
Are connected to the electrode pads 23a, 23b, 26 as shown in FIG. Here, the relationship between FIG. 1 and FIG. 2 will be described. The semiconductor device A of FIG. 2 schematically shows only a structure for detecting the vibration of the vibrator 11 of FIG. 1 in the Y-axis direction, and is connected in series between the electrode pads 23a and 23b of FIG. The capacitors Ca and Cb are connected to the comb-shaped electrode set 21.
a and 24a, and a capacitor formed by the comb-shaped electrode sets 21b and 24b, respectively. Then, the capacitors Ca and C shown in FIG.
The electrode pad 26 which is a connection point between the vibrator 11 and the beam 1 located in the middle of the comb-like electrode sets 24a and 24b in FIG.
It corresponds to the electrode pad 26 electrically connected through the 3c and the anchor 12c.

The capacitance change detection circuit includes a rectangular wave signal generation circuit 30 and a pulse train signal generation circuit 40. The rectangular wave signal generation circuit 30 generates a rectangular wave signal S1 having a frequency (for example, about 1 MHz) much higher than the resonance frequency of the vibrator 11 (see FIG. 3), and sends the rectangular wave signal to the electrode pad 23b. Supply. This square wave signal generation circuit 3
0 is connected to an inverting amplifier 31.
Inverts the rectangular wave signal from the rectangular wave signal generation circuit 30 and supplies a rectangular wave signal having the opposite phase to the same to the electrode pad 23a. The pulse train signal generation circuit 40 operates in synchronization with the rectangular wave signal generation circuit 30, and generates a first pulse train signal S3 and a second pulse train signal S4 (see FIG. 3) having the same period as the rectangular wave signal and opposite phases to each other. Output each. These first and second pulse train signals S3 and S4 are partially enlarged, as shown in FIG. 4, and immediately after the rectangular wave signal S1 changes from a high level to a low level and immediately after a change from a low level to a high level, After a short period of time, the pulse signal changes from a low level to a high level, and sequentially changes from a high level to a low level when the rectangular wave signal S1 changes from a low level to a high level and from a high level to a low level.

A charge amplifier 50 is connected to the electrode pad 26, and the output of the amplifier 50
And the second sample and hold circuits 60 and 70 are connected to each other. The charge amplifier 50 includes an operational amplifier OP
1, a capacitor C1 and a resistor R1, and inverts and amplifies a voltage signal extracted from a connection point between the capacitors Ca and Cb, and outputs it as a voltage signal S2 (see FIG. 3). The first sample and hold circuit 60 includes a switching circuit SW1 including a transistor, a capacitor C2, and an operational amplifier OP2, and samples and holds the output voltage of the charge amplifier 50 with the first pulse train signal S3 from the pulse train signal generation circuit 40. The second sample and hold circuit 70 includes a switching circuit SW2 including a transistor, a capacitor C3, and an operational amplifier O.
The output voltage of the charge amplifier 50 is sampled and held by the second pulse train signal S4 from the pulse train signal generation circuit 40.

The first and second sample and hold circuits 60,
Each output of the capacitor 70 is calculated by combining the respective outputs to obtain a capacitor C
a and Cb are connected to an arithmetic circuit 80 for extracting a signal representing a change in capacitance. The arithmetic circuit 80 includes resistors R2 to R5 and an operational amplifier OP4, and subtracts the output voltage of the second sample and hold circuit 70 from the output voltage of the first sample and hold circuit 60 and outputs the result to the output terminal OUT.

Next, the operation of the embodiment configured as described above will be described. A drive signal of a predetermined frequency f is supplied from the drive circuit B via the electrode pads 16a and 16b to the comb-like electrode 14.
a, 14b, the vibrator 11 has the comb-shaped electrode 1
Due to electrostatic attraction between the electrodes 4a and 17a and between the comb-shaped electrodes 14b and 17b, the oscillator oscillates at a frequency equal to the predetermined frequency f with a constant amplitude in the X-axis direction. In this state, when an angular velocity around the Z axis acts on the semiconductor element A, the vibrator 11 starts to vibrate in the Y axis direction with an amplitude proportional to the magnitude of the angular velocity.
Thereby, each electrode finger of the comb-teeth electrode set 24a, 24b approaches or separates from each adjacent opposing electrode finger of the comb-teeth electrode set 21a, 21b in synchronization with the vibration. In this case, if the distance between the adjacent electrode fingers of the comb-teeth electrode set 24a, 21a increases (or decreases), the comb-teeth electrode set 2
Since the distance between the adjacent electrode fingers 4b and 21b decreases (or increases), the capacitance of the capacitor Ca constituted by the comb-teeth electrode sets 24a and 21a and the comb-teeth electrode set 24
The capacitance of the capacitor Cb constituted by b and 21b increases and decreases in directions opposite to each other.

On the other hand, at both ends of the capacitors Ca and Cb,
A rectangular wave signal is applied from the rectangular wave signal generation circuit 30 and the inverting amplifier 31 via the electrode pads 23a and 23b. From the connection point between the capacitors Ca and Cb, the rectangular wave signal is transferred to the capacitors Ca and Cb. A voltage signal whose amplitude is modulated according to the change, that is, a voltage signal obtained by amplitude-modulating the rectangular wave signal with a signal indicating a change in capacitance of the capacitors Ca and Cb is obtained. Then, the charge amplifier 50 inverts and amplifies the voltage signal, and the inverted and amplified voltage signal S2
(Refer to FIG. 3) to the first and second sample and hold circuits 6
0, 70 respectively.

The first and second sample and hold circuits 60,
The first and second pulse signals S3 and S4 (see FIG. 3) from the pulse train signal generating circuit 40 are supplied to the sample and hold circuit 60 and 70. The sample and hold circuits 60 and 70 convert the voltage signal S2 into first and second signals. The sample and hold are performed by the pulse signals S3 and S4. Therefore, the first sample and hold circuit 6
0 means that only the positive side voltage of the voltage signal S2 is sequentially sampled and held, and the second sample and hold circuit 70 sequentially samples and holds only the negative side voltage of the voltage signal S2. The second sample-and-hold circuits 60 and 70 output voltage signals representing both the positive and negative angular velocities acting around the Z axis of the semiconductor element A, that is, changes in the capacitance of the capacitors Ca and Cb.

The output signals of the first and second sample and hold circuits 60 and 70 are output to the arithmetic circuit 80, respectively. The arithmetic circuit 80 subtracts the output signal of the second sample and hold circuit 70 (the negative voltage signal) from the output signal of the first sample and hold circuit 60 (the positive voltage signal), and outputs the result. The output signals from the two sample hold circuits 60 and 70 are substantially synthesized and output. As a result, a voltage signal S5 (see FIG. 3) representing the change in the capacitance of the capacitors Ca and Cb, that is, the angular velocity is output from the output terminal OUT of the arithmetic circuit 80.

In the present embodiment operating as described above, since the rectangular wave signal is applied to the pair of capacitors Ca and Cb, the pulse train is compared with the case where the sine wave signal is applied to the same pair of capacitors Ca and Cb. Signal generation circuit 4
0, without having to strictly control the sampling timing in the first and second sample and hold circuits 60 and 70,
Both sample and hold circuits 60 and 70 are provided with capacitors Ca and
A voltage signal S2 representing a change in capacitance of Cb, that is, the angular velocity.
Can be sampled accurately. Since the first and second sample-and-hold circuits 60 and 70 also function as low-pass filters, there is no need for a special low-pass filter for extracting a voltage signal S5 representing the change in the capacitance of the capacitors Ca and Cb, that is, the angular velocity. As a result, according to this embodiment, it is possible to detect a change in the capacitance of the pair of capacitors Ca and Cb, that is, the angular velocity, with a simple circuit configuration. Further, the omission of the low-pass filter eliminates the need to consider a phase delay of an output signal indicating a change in the capacitance of the pair of capacitors Ca and Cb.

Further, in the above-described embodiment, as shown in FIG.
And the second pulse train signals S3 and S4 become high level at a timing excluding a predetermined period immediately after the level change of the square wave signal S1, and control the sample and hold by the first and second sample hold circuits 60 and 70 at the high level. I did it. Therefore, the first and second sample-and-hold circuits 60 and 70 can operate both capacitors without being affected by a transient change in the potential at the connection point between the pair of capacitors Ca and Cb immediately after the level change of the rectangular wave signal S1. A signal indicating the change in capacitance of Ca and Cb can be sampled and held, and the sampled and held signal can be output, so that the change in capacitance of the capacitors Ca and Cb can be accurately detected.

Further, in the above embodiment, the pulse train signal generation circuit 40 has the same period as the period of the rectangular wave signal S1 and has the first phase opposite to each other corresponding to the low level and the high level of the rectangular wave signal S1, respectively. And second pulse train signals S3 and S4, and the first and second pulse train signals S3 and S4 are generated.
Sampling in the first and second sample and hold circuits 60 and 70 is controlled by the pulse train signals S3 and S4, and the first and second sample and hold circuits 60 and 70 are controlled.
Are output by the arithmetic circuit 80 to output a combined result. Therefore, even if noise is mixed into the semiconductor element A and an unnecessary noise component is included in the voltage signal at the connection point between the pair of capacitors Ca and Cb, the noise component is canceled out, and the noise of the capacitors Ca and Cb is reduced. The change in capacitance, that is, the angular velocity is accurately detected.

In the above embodiment, an AC signal (AC signal having a resonance frequency f of the vibrator 11) representing a change in the capacitance of the pair of capacitors Ca and Cb (displacement of the vibrator 11 in the Y-axis direction) is used. Output terminal O of arithmetic circuit 80
Output from UT. However, when it is desired to extract a signal representing the angular velocity around the Z axis acting on the semiconductor element A as a DC signal, a detection circuit for detecting the resonance frequency f is connected to the output terminal OUT. The AC signal from the output terminal OUT may be detected at the resonance frequency f and smoothed to extract a DC signal representing the angular velocity. When it is desired to extract the signal representing the angular velocity as a digital signal, the DC signal representing the angular velocity may be converted into a digital signal by an A / D converter and output.

In the above embodiment, the pulse train signal generating circuit 40 has the same period as that of the rectangular wave signal S1 (the period of "1" times the period of the rectangular wave signal S1), and the first and second signals having phases opposite to each other. The second pulse train signals S3 and S4 are output. However, when the frequency of the rectangular wave signal S1 is sufficiently high, it is not necessary to take out the low-level signal and the high-level signal adjacent to the voltage signal S2 output from the charge amplifier 50.
From the first and second pulse train signals having a period that is an integral multiple of “2” or more of the period of the rectangular wave signal S1 and corresponding to the high level and the low level of the rectangular wave signal, respectively, And second sample and hold circuits 60 and 7
0, the voltage signal S is generated by the first and second pulse train signals.
2 may be sampled and held.

As described above, the capacitors Ca and C are output from the first and second sample and hold circuits 60 and 70, respectively.
b, a voltage signal representing both the positive and negative angular velocities acting around the Z-axis of the semiconductor element A is output.
If there is no problem of noise contamination at the connection point between the first and second pulse trains, one of the first and second sample and hold circuits 60 and 70 and the arithmetic circuit 80 are omitted, and the pulse train signal generation circuit 40 Signals S3 and S4
May be generated. Also in this case, as described above, the pulse train signal generation circuit 40 is configured to generate a pulse train signal having the same cycle as the rectangular wave signal S1 (a cycle of "1" times the cycle of the rectangular wave signal S1). Alternatively, the generator 40 may be configured to generate a pulse train signal having a cycle that is an integral multiple of “2” or more of the cycle of the rectangular wave signal S1.

Further, in the above embodiment, the example in which the present invention is applied to the angular velocity sensor has been described. However, the displacement of the vibrator 11 in the Y-axis direction can be performed without vibrating the vibrator 11 in the X-axis direction. The present invention can also be applied to an acceleration detection device that detects the acceleration in the Y-axis direction acting on the semiconductor element by detecting the acceleration. Also in this case, the point that the capacitance change of the capacitor Ca formed by the comb-teeth electrode sets 24a, 21a and the capacitance change of the capacitor Cb formed by the comb-teeth electrode sets 24b, 21b is the same as in the above-described embodiment. . The present invention is not limited to the angular velocity detection device and the acceleration detection device, but may be applied to any device that detects a change in capacitance of a pair of capacitors connected in series.

[Brief description of the drawings]

FIG. 1 is an overall schematic diagram of an angular velocity detection device to which a capacitance change detection circuit according to the present invention is applied.

FIG. 2 is a detailed block diagram of the capacitance change detection circuit of FIG.

FIG. 3 is a signal waveform diagram of each unit in FIG. 2;

FIG. 4 is an enlarged view in which a part of the signal waveform diagram of FIG. 3 is enlarged.

[Explanation of symbols]

A: semiconductor element, B: drive circuit, C: capacitance change detection circuit, 10: substrate, 11: vibrator, 14a, 14b, 17
a, 17b ... comb-shaped electrodes, 21a, 21b, 24a, 2
4b: comb-shaped electrode set, Ca, Cb: capacitor, 30 ...
Square wave signal generation circuit, 40... Pulse train signal generation circuit, 5
0: charge amplifier, 60, 70: sample and hold circuit, 80: arithmetic circuit.

Claims (3)

[Claims] 1. A capacitance change detecting device for applying a voltage signal to both ends of a pair of capacitors connected in series and detecting a capacitance change of the same pair of capacitors based on a voltage signal taken out from a connection point between the same pair of capacitors. In the circuit device, a rectangular wave signal generation circuit that generates a rectangular wave signal and applies the same rectangular wave signal to both ends of the pair of capacitors, and generates a pulse train signal having a period that is an integral multiple of the period of the rectangular wave signal A capacitance change detection circuit device, comprising: a pulse train signal generation circuit; and a sample hold circuit that samples and holds a voltage signal taken out from the connection point with the pulse train signal. 2. The pulse train signal according to claim 1,
A capacitance change detection circuit device that controls the sample and hold at a timing except for a predetermined period immediately after the level change of the rectangular wave signal. 3. Capacitance change detection for applying a voltage signal to both ends of a pair of capacitors connected in series and detecting a capacitance change of the same pair of capacitors based on a voltage signal taken out from a connection point between the same pair of capacitors. In the circuit device, a rectangular wave signal generating circuit that generates a rectangular wave signal and applies the rectangular wave signal to both ends of the pair of capacitors, the rectangular wave signal having a period that is an integral multiple of the period of the rectangular wave signal A pulse train signal generation circuit for generating first and second pulse train signals respectively corresponding to the high level and the low level of the first and second voltage trains;
A first and a second sample-and-hold circuit for sampling and holding with a pulse train signal, and an operation for synthesizing each output of the first and the second sample-and-hold circuits to extract a signal representing a change in capacitance of the pair of capacitors. And a circuit for detecting a change in capacitance.