JP3449255B2 - Amplifier circuit device - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an angular velocity detecting device,
The present invention relates to an amplifier circuit device that is applied to an acceleration detection device or the like and that is connected to the middle of a pair of capacitors connected in series and that outputs a signal indicating the capacitance change of the capacitors.

[0002]

2. Description of the Related Art Conventionally, a voltage representing a capacitance change of a capacitor of the same pair formed by a comb-shaped electrode mechanically connected to a vibrator and electrically transferred in series to a pair of capacitors. It is well known to take out a signal and detect angular velocity, acceleration, etc. by the signal. In this type of device, as disclosed in, for example, Japanese Patent Laid-Open No. 10-90742,
A midpoint of the pair of capacitors is connected to the inverting input terminal of the operational amplifier, a DC bias voltage is applied to the non-inverting input terminal of the amplifier, and a feedback capacitor is provided between the output terminal and the inverting input terminal of the amplifier. An amplifier circuit device in which a resistor and a resistor are connected in parallel has been used.

[0003]

In the amplifier circuit device configured as described above, it is preferable to reduce the capacitance of the feedback capacitor as much as possible in order to enhance the capability of detecting the capacitance change of the pair of capacitors. On the other hand, reducing the capacitance of the feedback capacitor means reducing the time constant determined by the capacitor and the resistor. If this time constant becomes too small, the capacitance change of the pair of capacitors is represented. AC signal cannot be taken out.
On the other hand, in this amplifier circuit device, since the operational amplifier is used, a feedback resistor for applying a DC bias voltage to the inverting input terminal is always necessary, and the value of the resistor is increased. In reality, there is a limit due to problems such as accuracy. Therefore, the feedback capacitor cannot be made sufficiently small, and the capacity change detection capability of the pair of capacitors cannot be sufficiently improved.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object thereof is to sufficiently reduce the capacitance of a feedback capacitor by eliminating the need for providing the conventional feedback resistor. Therefore, it is another object of the present invention to provide an amplifier circuit device capable of sufficiently enhancing the capacity change detection capability of a pair of capacitors.

In order to achieve the above object, a structural feature of the present invention is that an input terminal is connected in the middle of a pair of capacitors connected in series, and a feedback capacitor is provided between the input terminal and the output terminal. In an amplifier circuit device that outputs a voltage signal indicating the capacitance change of the same pair of capacitors from the output end by the movement of electric charge to the pair of capacitors, the amplifier circuit device is connected to the input end and input to the same input end. An input bias circuit that applies a bias voltage and an output bias circuit that is connected to the output terminal and that applies an output bias voltage to the output terminal are provided so that gain in the DC region is eliminated and operation is performed only in the AC region. There is something I did.

In this case, in the amplifier circuit device, for example, a transistor is provided between the input terminal and the output terminal, the base of the transistor is connected to the input terminal, the capacitor is connected to the emitter of the transistor, and The collector of the transistor can be connected to the output.

In the present invention constructed as described above,
While applying an input bias voltage to the input terminal, and applying an output bias voltage to the output terminal, the gain in the DC region is eliminated and the operation is performed only in the AC region.
The resistor connected in parallel to the feedback capacitor was not used. As a result, according to the present invention, the capacitance of the feedback capacitor can be made sufficiently small, so that the capacity change detection capability of the pair of capacitors can be sufficiently enhanced.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION An 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 an amplifier circuit device according to the present invention is applied.

This angular velocity detecting device rotates around the Z-axis (see FIG. 1) while vibrating the oscillator in the X-axis direction (left-right direction in FIG. 1).
When the angular velocity acts around (in the direction perpendicular to the paper surface of FIG. 2), the angular velocity is detected by utilizing the fact that the oscillator vibrates in the Y-axis direction (left and right direction in FIG. 1) with an amplitude proportional to the angular velocity due to the Coriolis force. A semiconductor element A incorporating the same vibrator, a constant voltage source circuit B for supplying a DC power supply voltage to various electric circuits, and a vibrator X connected to the semiconductor element A for connecting the vibrator X
A driving circuit C for driving in the axial direction and an angular velocity signal extracting circuit D for extracting an angular velocity signal representing the angular velocity by vibrating the vibrator in the Y-axis direction, which is connected to the semiconductor element A.
It has and.

First, the semiconductor element A will be described. The semiconductor element A has a rectangular oscillator 11 provided on a central portion of a rectangular substrate 10 so as to be floated over a predetermined distance.
The oscillators 11 are anchors 12 a to 1 a fixed on the substrate 10.
A beam 13a which is connected to 2d at its outer end and which is provided at a predetermined distance above the substrate 10 like the vibrator 11.
13d to 13d support the substrate 10 so as to be displaceable in the X-axis direction and the Y-axis direction in the horizontal plane.

The substrate 1 is provided on each outside of the vibrator 11 in the X-axis direction.
0 is provided with comb-tooth-shaped electrodes 14a and 14b, respectively, and each comb-tooth-shaped electrode 14a and 14b is provided with a plurality of electrode fingers extending in the X-axis direction and arranged at equal intervals in the Y-axis direction. Is equipped with. In addition, each of the comb-shaped electrodes 14a, 14
Pad portions 15a and 15b fixed to the substrate 10 and connected to the comb-teeth-shaped electrodes 14a and 14b are provided on the respective outer sides of b in the X-axis direction.
Electrode pads 16a and 16b formed of a conductive metal (for example, aluminum) in a rectangular shape are provided on a and 15b, respectively.

The vibrator 1 is provided on the side of the vibrator 11 in the X-axis direction.
1, comb-shaped electrodes 17a and 17b are provided integrally with the vibrator 11 so as to float above the substrate 10 by a predetermined distance. Each of the comb-teeth electrodes 17a and 17b is provided with a plurality of electrode fingers extending outward in the X-axis direction and arranged at equal intervals in the Y-axis direction. 14b penetrates in the center position between the electrode fingers in the width direction (Y-axis direction). The comb-teeth electrodes 14a and 14b together with the comb-teeth electrodes 17a and 17b form a drive unit for the vibrator 11.
1 is excited in the X-axis direction by electrostatic attraction when the drive signal is applied to the comb-shaped electrodes 14a and 14b.

The substrate 1 is provided on each outside of the vibrator 11 in the Y-axis direction.
A plurality of comb-teeth-shaped electrode sets 21a and 21b fixed on the 0 are provided respectively, and the comb-teeth-shaped electrode sets 21a and 21b are respectively provided.
Is provided with a plurality of electrode fingers extending in the X-axis direction and arranged at equal intervals in the Y-axis direction. In addition, the substrate 10 is provided outside each of the comb-teeth electrode sets 21a and 21b in the Y-axis direction.
Each of the comb-teeth-shaped electrode sets 21a and 21b is fixed to the top
Pad portions 22a and 22b connected to the respective electrodes, and electrode pads 23 formed on the pad portions 22a and 22b in a rectangular shape with a conductive metal (for example, aluminum).
a and 23b are provided respectively.

The vibrator 1 is provided on the Y-axis side of the vibrator 11.
A plurality of comb-teeth-shaped electrode sets 24, which are integrally formed with the vibrator 11 by floating a predetermined distance above the substrate 10 as in the case of 1.
a and 24b are provided respectively. Comb-shaped electrode set 2
4a and 24b are provided with a plurality of electrode fingers that extend in the X-axis direction and are arranged at equal intervals in the Y-axis direction, and these electrode fingers are electrodes of the comb-teeth-shaped electrode sets 21a and 21b. It has penetrated between the fingers. However, the comb-teeth-shaped electrode set 24
The electrode fingers of a are displaced from the center position in the width direction between the electrode fingers of the comb-tooth-shaped electrode set 21a, and are located outside the electrode fingers of the comb-tooth-shaped electrode set 21a in the Y-axis direction. The electrodes are close to each other, and the electrode fingers close to each other form a capacitor. Further, each electrode finger of the comb-tooth-shaped electrode set 24b is also displaced from the center position in the width direction between the electrode fingers of the comb-tooth-shaped electrode set 21b, and is outside the Y-axis direction of each electrode finger of the same comb-tooth-shaped electrode set 21b. The electrode fingers are close to each other, and the electrode fingers close to each other form a capacitor.

The comb-tooth-shaped electrode sets 21a and 21b form a detection section for the vibration of the vibrator 11 together with the comb-tooth-shaped electrode sets 24a and 24b. If the distance between the pair of adjacent electrode fingers of the comb-shaped electrode pairs 21a and 24a and the distance between the pair of adjacent electrode fingers of the comb-tooth-shaped electrode pairs 21b and 24b increases when the distance increases, It increases or decreases in opposite directions so that the other distance decreases. That is, when the total capacitance of the capacitors (hereinafter, referred to as capacitors Ca) formed by the adjacent electrode fingers of the comb-teeth electrode set 21a and the comb-teeth electrode set 24a increases (or), the comb-teeth electrode set 21b and The total capacitance of the capacitors (hereinafter, referred to as capacitors Cb) formed by the adjacent electrode fingers of the comb-teeth-shaped electrode set 24b decreases (or increases).

Further, on the substrate 10, a pad portion 25 fixed to the substrate 10 and connected to the anchor 12c is provided.
Is provided on the pad portion 25, and an electrode pad 26 formed of a conductive metal (for example, aluminum) in a rectangular shape is provided on the pad portion 25.

A method of manufacturing the semiconductor device A having such a structure will be briefly described. First, SO 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 with an intermediate layer made of a silicon oxide film interposed therebetween.
An I (Silicon-On-Insulator) substrate is prepared, and the upper layer is doped with impurities such as phosphorus and boron to reduce the resistance of the upper layer. Next, the vibrator 11, the anchors 12a to 12d, the beams 13a to 13d, the comb-teeth electrodes 14a, 14b, 17a,
17b, comb-tooth-shaped electrode pairs 21a, 21b, 24a, 24b
And the upper surface of the upper part of the portions corresponding to the pad portions 15a, 15b, 22a, 22b, 25 is masked with a resist film,
The upper layer and the intermediate layer other than the above portion are removed by etching by reactive ion etching or the like. As a result, the anchors 12a to 12d, the comb-teeth-shaped electrodes 14a and 14b, the comb-teeth-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 oscillator 11, the beams 13a to 13d, the comb-teeth electrodes 17a and 17b, and the comb-teeth electrode sets 24a and 24.
The intermediate layer corresponding to b is removed by etching with an aqueous solution of hydrofluoric acid or the like, and the vibrator 11, the beams 13a to 13d, the comb-shaped electrodes 17a and 17b, and the combs which are floated from the substrate 10 by a predetermined distance are removed. Toothed electrode set 24a, 24b
To form. Then, the pad portions 15a, 15b, 22
a, 22b, 25 on the electrode pads 16a, 16b, 2
3a, 23b and 26 are formed. In the semiconductor element A thus configured, the upper layer has a low resistance as described above, and therefore the vibrator 11 and the anchors 12a to 12a.
The d, the beams 13a to 13d, the comb-teeth electrodes 17a and 17b, the comb-teeth electrode groups 24a and 24b, the pad portion 25, and the electrode pad 26 are electrically connected in a state close to a conductor. Further, the comb-teeth electrode 14a, the pad portion 15a and the electrode pad 16a, the comb-teeth electrode 14b, the pad portion 15b and the electrode pad 16b, the comb-teeth electrode set 21a, the pad portion 22a and the electrode pad 23a, and the comb. Toothed electrode set 2
1b, the pad portion 22b, and the electrode pad 23b are also electrically connected to each other independently in a state close to a conductor.

The constant voltage source circuit B inputs a DC voltage from a battery (not shown), converts the DC voltage into various voltages, and is necessary for circuits such as the drive circuit C and the angular velocity signal extraction circuit D. It supplies the corresponding power supply voltage. In particular, since the constant voltage source circuit B supplies a high DC voltage to a circuit that requires a high power supply voltage to drive the vibrator 11 like the drive circuit C, the input DC voltage is set to a predetermined value. It has a built-in booster circuit that boosts the voltage to a high voltage.

An example of this booster circuit is shown in FIG.
In this booster circuit, a constant current circuit 32 and a PNP transistor 33 are provided between the power supply line 31 and ground.
Of the transistor 33 and the emitter of the transistor 33 are connected in series. In addition, the arrow in a figure shows the direction of an electric current. A reference voltage source 34 that generates a reference voltage Vref is connected between the base of the transistor 33 and the ground, and the collector of the transistor 33 is grounded. At the connection point between the constant current circuit 32 and the emitter of the transistor 33, a plurality (four in this embodiment) of diodes 35a to 35d are connected in series with the anode side as the connection point side, and the diode at the final stage is connected. The cathode side of 35d is connected to the output terminal OUT. A capacitor 36a is provided on the cathode side of each of the diodes 35a to 35d.
One end of each of ~ 36d is connected.

The other ends of the capacitors 36a and 36c are connected to the output end of an inverter 38a which receives the clock signal from the oscillator 37 and inverts the clock signal.
The other end of the capacitor 36b has an inverter 38b that inverts the inverted clock signal from the inverter 38a again.
Is connected to the output end of. Each clock signal output from the oscillator 37 and the inverters 38a and 38b has a predetermined frequency (for example, several tens KHz) in which a low level (ground voltage) with a duty ratio of 1/2 and a high level (reference voltage Vref) are alternately repeated. ) Is a rectangular wave pulse train signal. The other end of the capacitor 36d is grounded. The connection line between each of the inverters 38a and 38b and the emitter of the transistor 33 is for supplying a power supply voltage to the inverters 38a and 38b.

The operation of the booster circuit thus configured will be briefly described. The transistor 33 is the reference voltage source 34.
The constant current from the constant current circuit 32 always flows to the ground via the transistor 33. At this time, the voltage of the emitter of the transistor 33 is maintained at approximately the reference voltage Vref (specifically, the value obtained by adding the emitter-base voltage of the transistor 33 to the reference voltage). In this state, the inverter 38a
When the clock signal from is low level, current flows into the capacitor 36a via the diode 35a,
The capacitor 36a is charged to a reference voltage Vref (more precisely, a voltage lower than the emitter voltage of the transistor 33 by the voltage drop of the diode 35a).

Next, when the clock signal from the inverter 38a becomes high level, the potential of the capacitor 36a on the diodes 35a and 35b side rises to a voltage higher by the reference voltage. At this time, since the clock signal from the inverter 38b is at the low level, the capacitor 36b is charged by the increased voltage of the capacitor 36a. Then, next, when the clock signal from the inverter 38b becomes high level, the potentials of the capacitors 36b on the diodes 35b and 35c side rise to a voltage higher than the charged voltage by the reference voltage. And
At this time, since the clock signal from the inverter 38a is at a low level, the capacitor 36c is charged by the increased voltage of the capacitor 36b.

In this way, the capacitors 36a-36
The terminal voltage of the diode d on the side of the diodes 35a to 35d is sequentially controlled to be increased by the clock signals from the oscillator 37 and the inverters 38a and 38b, and a voltage sufficiently higher than the reference voltage Vref is taken out from the output terminal OUT. Also,
In this booster circuit, charging and discharging of the capacitors 36a to 36d are performed intermittently, and the current value due to this charging and discharging is relatively large. However, the constant current circuit 32 is used, and the DC power supply (power supply line) 31 and Since the current flowing to the ground is always made almost constant, radiation such as radio noise can be reduced. The transistor 33 of the booster circuit is changed to an operational amplifier 39 as shown in FIG. 3, and the voltage on the anode side of the diode 35a is changed to the reference voltage V.
The current from the constant current circuit 32 may always flow into the operational amplifier 39 from its output terminal while being kept at ref. In this case, the reference voltage source 34 is connected to the non-inverting input of the operational amplifier 39, and the output terminal and the inverting input terminal are short-circuited.

The drive circuit C is connected to the constant voltage source circuit B and also to the electrode pads 16a and 16b, and has an oscillator, an amplifier and the like inside. The oscillator oscillates a signal of a predetermined frequency (for example, about 10 KHz) substantially equal to the resonance frequency of the vibrator 11, and the output of the oscillator is transmitted through the amplifier to the electrode pads 16a, 16.
b. The electrode pads 16a and 16b are supplied with oscillation signals having opposite phases to each other as driving signals.

As shown in FIGS. 1 and 4, the angular velocity signal extraction circuit D includes electrode pads 23a, 23 of the semiconductor element A.
b, 26 and the constant voltage source circuit B. Here, the relationship between FIG. 1 and FIG. 4 will be described. The semiconductor element A of FIG. 4 schematically shows only the 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 composed of the comb-teeth electrode sets 21a and 24a, and the comb-teeth electrode sets 21b and 24b.
And a capacitor configured by. The electrode pad 26, which is the connection point between the capacitors Ca and Cb in FIG. 4, is the comb-teeth electrode set 24a, 2 in FIG.
It corresponds to the electrode pad 26 electrically connected via the vibrator 11, the beam 13c and the anchor 12c located in the middle of 4b.

The angular velocity signal extraction circuit D is provided with a high frequency oscillator D1, an amplification circuit D2, a demodulation circuit D3 and a synchronous detection circuit D4 which are operated by the power supply voltage supplied from the constant voltage source circuit B. The high frequency oscillator D1 generates a sinusoidal high frequency signal having a frequency (for example, about 1 MHz) much higher than the resonance frequency of the vibrator 11, and supplies the high frequency signal to the electrode pad 23b. An inverting amplifier 41 is connected to the high-frequency signal generation circuit D1, which inverts the high-frequency signal from the high-frequency signal generation circuit D1 and outputs a sinusoidal high-frequency signal having a phase opposite to that of the high-frequency signal generation circuit D1 to the electrode pad 23a. Supply to.

The amplifier circuit D2 has an input terminal IN connected to the electrode pad 26, and has a pair of capacitors Ca and Cb.
Of the same pair of capacitors Ca, C
A voltage signal indicating the capacitance change of b is output from the output terminal OUT. The input terminal IN has a positive power supply voltage V
It is connected to the gate of a field effect transistor (FET) 43 having a drain connected to a DC power supply (power supply line) 42 for supplying cc, and the source of the FET 43 is grounded via a constant current circuit 44 for current bias. The arrows in the figure represent the direction of current flow. The FET 43 constitutes a voltage follower, and a resistor 45 and a DC power supply 46 connected in series are connected between its gate and ground. The resistor 45 functions as an input resistance of the amplifier circuit D2, and the DC power supply 46 constitutes an input bias circuit that applies an input bias voltage.

The source of the FET 43 is an NPN for inverting amplification.
A transistor 48 of the same type is connected to the base of the transistor 47, and a capacitor 48 and a constant current circuit 49 for current bias are connected in parallel between the emitter of the transistor 47 and the ground. The collector of the transistor 47 is connected to the emitter of a transistor 51 of NPN type for amplification whose collector is connected to the output terminal OUT, and a predetermined DC voltage is supplied from a DC power supply 52 to the base of the transistor 51. Has been done. A constant current circuit 53 for current bias is connected between the collector (output terminal OUT) of the transistor 51 and the DC power supply (power supply line) 42, and between the collector (output terminal OUT) and the input terminal IN. A feedback capacitor 54 is connected to the. Further, between the collector (output terminal OUT) of the transistor 51 and the ground, a capacitor 55 for phase compensation is connected, and a resistor 56 and a DC power supply 57 connected in series are connected. The resistor 56 functions as an output resistance of the amplifier circuit D2, and the DC power supply 57 constitutes an output bias circuit that applies an output bias voltage.

The characteristic of the amplifier circuit D2 configured as above is that DC bias voltages are applied to the input terminal IN and the output terminal OUT by the DC power supplies 46 and 57, and the capacitor 48 is provided.
Thus, by eliminating the gain in the DC region, the feedback resistor normally provided in parallel with the feedback capacitor 54 is eliminated. This allows the condenser 54
The capacitance of the semiconductor element A can be reduced, and
The ability to detect a capacitance change due to charge transfer of a and Cb is enhanced. The transistors 43, 47, 51
The gain G of the amplifying circuit consisting of G = ω is determined by the capacitance C ₄₈ of the capacitor ₄₈ and the resistance value R ₅₆ of the resistor _56.
C ₄₈ R ₅₆ (ω is each frequency of the input signal).

The demodulation circuit D3 is connected to the output terminal OUT of the amplifier circuit D2 and synchronously detects the signal from the output terminal OUT at the same frequency as the frequency of the high frequency signal generated by the high frequency oscillator D1. Capacitors Ca and C
The signal indicating the capacitance change of b (the signal indicating the vibration of the vibrator 11 in the Y-axis direction) is extracted and output. In other words, the signal at the intermediate point between the capacitors Ca and Cb is the high frequency signal from the high frequency oscillator D1.
Since it is a signal that is amplitude-modulated with a signal that represents the capacitance change of
The demodulation circuit D3 extracts a signal indicating a capacitance change of the capacitors Ca and Cb, which is a modulation signal obtained by amplitude-modulating the high frequency signal.

The synchronous detection circuit D4 is connected to the demodulation circuit D3 and outputs a signal (a signal representing the vibration of the vibrator 11 in the Y-axis direction) indicating the capacitance change of the capacitors Ca and Cb from the circuit D3. The amplitude envelope of the signal is taken out by synchronous detection at the vibration frequency of 11 in the Y-axis direction. In other words, the amplitude of the signal indicating the capacitance change of the capacitors Ca and Cb (the signal indicating the vibration of the oscillator 11 in the Y-axis direction) is proportional to the angular velocity of the semiconductor element A about the Z-axis. D4 is for extracting a signal representing the angular velocity.

Next, the operation of the embodiment configured as described above will be described. A drive signal of a predetermined frequency is output from the drive circuit B via the electrode pads 16a and 16b to the comb-teeth-shaped electrodes 14a,
14b, the vibrator 11 becomes a comb-shaped electrode 14
The electrostatic attraction between a and 17a and between the comb-teeth-shaped electrodes 14b and 17b causes vibration at a constant amplitude in the X-axis direction at a frequency equal to the predetermined frequency. 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 X axis direction with an amplitude proportional to the magnitude of the angular velocity. As a result, the electrode fingers of the comb-tooth-shaped electrode sets 24a and 24b move closer to or away from the electrode fingers of the comb-tooth-shaped electrode sets 21a and 21b that are in close proximity to each other 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 24
Since the distance between the adjacent electrode fingers of b and 21b decreases (or increases), the capacitance of the capacitor Ca formed by the comb-teeth electrode sets 24a and 21a and the comb-teeth electrode set 24
The capacitance of the capacitor Cb formed by b and 21b increases or decreases in the opposite directions.

On the other hand, at both ends of the capacitors Ca and Cb,
Electrode pad 2 from high frequency oscillator D1 and inverting amplifier 41
A high-frequency signal is applied via 3a and 23b, and a voltage signal obtained by amplitude-modulating the high-frequency signal according to the capacitance change of the capacitors Ca and Cb is obtained from the connection point between the capacitors Ca and Cb. Then, the amplifier circuit D2 inverts and amplifies the voltage signal, and supplies the inverted and amplified voltage signal to the demodulation circuit D3. The demodulation circuit D3 is a high frequency oscillator D
1 is used to demodulate the inverted and amplified voltage signal using the same frequency as the frequency of the high-frequency signal to generate a signal indicating the capacitance change of the capacitors Ca and Cb (representing the vibration of the vibrator 11 in the Y-axis direction). Signal) to the synchronous detection circuit D4. The synchronous detection circuit D4 is a signal (Y of the oscillator 11) indicating the capacitance change of the capacitors Ca and Cb from the demodulation circuit D3.
(A signal representing vibration in the axial direction) is synchronously detected at the vibration frequency of the vibrator 11 in the Y-axis direction, and a signal representing the angular velocity of the semiconductor element A about the Z-axis is output.

In such an operation, since only the capacitor 54 is used in the feedback circuit, the capacitance of the capacitor 54 can be made sufficiently small, and the capacitance changes of the capacitors Ca and Cb (Y of the vibrator 11). Axial vibration)
It is possible to sufficiently increase the detection capability of. As a result, the angular velocity detection capability can be improved and the detection accuracy can be improved.

In the amplifier circuit D2 of the above embodiment, the transistor 51 functions to avoid the influence of the parasitic capacitance between the base and collector of the transistor 47 in order to operate the amplifier circuit D2 even in a very high frequency region. Are those that have. Therefore, the transistor 51 and the DC power supply 52 can be omitted when it is not necessary to operate up to a very high frequency region affected by the parasitic capacitance between the base and collector of the transistor 47.

Further, since the constant current circuit 53 and the DC power source 57 enable the amplifier circuit D2 to operate even at a low voltage, the voltage of the DC power source 42 is sufficiently high and the constant current circuit 53.
If the amplifier circuit D2 can be operated without the DC power supply 57, the identification current circuit 53 and the DC power supply 5
7 is omitted and the output resistor 56 is connected to the DC power source 4
2 and the collector (output terminal OUT) of the transistor 51. In this case, the DC power supply 42 functions as an output bias circuit for applying the output bias voltage.

Further, in the above embodiment, the example in which the present invention is applied to the angular velocity sensor has been described, but 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 and detects the acceleration in the Y-axis direction that acts on the semiconductor element. Also in this case, the point that the capacitance change of the capacitor Ca formed by the comb-teeth electrode sets 17a and 21a and the capacitor Cb formed by the comb-teeth electrode sets 17b and 21b is detected is the same as in the above-described embodiment. is there. Further, the amplifier circuit according to the present invention is not limited to the angular velocity detection device and the acceleration detection device, and the amplification circuit according to the present invention can be widely applied as long as it detects a capacitance change of a pair of capacitors connected in series by movement of charges.

[Brief description of drawings]

FIG. 1 is an overall schematic view of an angular velocity detection device to which an amplifier circuit according to the present invention is applied.

FIG. 2 is a detailed block diagram of a booster circuit provided in the constant voltage source circuit of FIG.

FIG. 3 is a detailed block diagram showing a modified example of the booster circuit of FIG.

4 is a detailed block diagram of the angular velocity extraction circuit of FIG.

[Explanation of symbols]

A ... Semiconductor element, B ... Constant voltage source circuit, C ... Driving circuit, D
... angular velocity extraction circuit, D1 ... high frequency oscillator, D2 ... amplification circuit, D3 ... demodulation circuit, D4 ... synchronous detection circuit, 10 ... substrate, 11 ... vibrator, 14a, 14b, 17a, 17b ...
Comb-shaped electrodes, 21a, 21b, 24a, 24b ... Comb-shaped electrode set, Ca, Cb ... Capacitors, 42, 46, 52,
57 ... DC power supply, 44, 49, 53 ... Constant current circuit, 4
5, 56 ... Resistors, 43, 47, 51 ... Transistors, 4
8, 54, 55 ... Capacitors.

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01C 19/56 G01P 9/04 G01R 27/26 H03F 3/70

Claims (2)

(57) [Claims] 1. An input terminal is connected to the middle of a pair of capacitors connected in series, and a feedback capacitor is connected between the input terminal and the output terminal, and a charge is transferred to the pair of capacitors. In an amplifier circuit device for outputting a voltage signal indicating the capacitance change of the pair of capacitors from the output end, an input bias circuit connected to the input end and applying an input bias voltage to the input end, and connected to the output end And an output bias circuit for applying an output bias voltage to the same output terminal to eliminate the gain in the DC region and operate only in the AC region. 2. A transistor is provided between the input end and the output end according to claim 1, the base of the transistor is connected to the input end, the emitter of the transistor is connected to a capacitor, and the transistor is connected. An amplifier circuit device in which the collector of is connected to the output terminal.