JP5559733B2 - Physical quantity sensor - Google Patents

Description

  The present invention relates to a physical quantity sensor that detects a physical quantity in accordance with vibrations in a sensor unit, and more particularly to detection processing for an output signal of a sensor unit.

  Currently, a vibration type gyroscope using a piezoelectric vibrator or the like is widely used as an angular velocity sensor. The vibration type gyroscope detects angular velocity from Coriolis force applied to a vibrating object, and drives the vibrator with an oscillation signal generated by a drive circuit. The vibrator outputs a detection signal having a frequency corresponding to the oscillation signal. Since the Coriolis force is proportional to the velocity of the vibrating object, the amplitude of the detection signal changes according to the angular velocity. Therefore, the detection circuit synchronously detects the detection signal and extracts an output signal corresponding to the angular velocity.

  10 and 11 are block diagrams of a vibration gyroscope 2 that employs a conventional synchronous detection method. The sensor element 4 uses a piezoelectric vibrator, and the drive generates an oscillation signal S01 that drives the sensor element 4. FIG. The circuit 6 includes a detection circuit 8 that synchronously detects the detection signal S02 from the sensor element 4 and extracts an angular velocity signal S03 of a DC voltage signal proportional to the angular velocity.

  The drive circuit 6 forms an oscillation loop using an AGC (Automatic Gain Control) amplifier 10. The AGC amplifier 10 receives the reference voltage Vref from the reference voltage generation circuit 12, and controls the oscillation signal S01 to an excitation level corresponding to the Vref.

  In the configuration shown in FIG. 10, the oscillation signal S01 from the drive circuit 6 and the detection signal S02 from the sensor element 4 are phase-adjusted and multiplied by the multiplication circuit 14, and an LPF (Low Pass Filter) is obtained from the multiplied signal. The angular velocity signal S03 is extracted by a (pass filter) 16 (Patent Document 1).

  In the configuration shown in FIG. 11, the detection circuit 8 includes amplifier circuits 20a and 20b. The amplifier circuit 20a outputs an amplified signal (X) of the detection signal S02, and the amplifier circuit 20b outputs an amplified signal (-X) with the polarity reversed. The rectification detection circuit 22 performs a switching operation at the same frequency as the oscillation signal S01, and generates the rectified signal | X | by alternately outputting the outputs (X) and (−X) of the two amplifier circuits 20. The LPF 16 smoothes the rectified signal | X | and extracts the angular velocity signal S04 (Patent Document 2).

JP-A-63-241308 JP 2009-229447 A

  The detection signal S02 is proportional to the excitation level of the sensor element 4 due to the oscillation signal S01. The excitation level of the oscillation signal S01 is basically proportional to Vref. That is, in the synchronous detection method shown in FIG. 10, both the detection signal S02 and the oscillation signal S01 input to the multiplication circuit 14 are proportional to the reference voltage Vref, and the output signal of the multiplication circuit 14 is proportional to the square of Vref. Therefore, the detection sensitivity of the angular velocity signal S03 is proportional to the square of Vref. This causes a problem that the error of Vref doubles and propagates to the angular velocity signal S03.

  On the other hand, the processing in the rectification detection circuit 22 of the method shown in FIG. 11 corresponds to multiplying the detection output S02 by a rectangular wave. When the frequency of the oscillation signal S01 is represented by f, the rectangular wave includes a component of an odd multiple of f (hereinafter referred to as “fodd”). Here, for example, a part of the vibration energy of the electric signal in the electronic circuit can be converted into the mechanical vibration of the substrate. Therefore, when an electric signal having the frequency fodd exists in the circuit formed on the substrate on which the gyroscope is mounted, The vibrator of the sensor element 4 is excited in a higher-order vibration mode by mechanical external vibration caused by the electric signal, and a noise component of the frequency fodd appears in the detection signal S02. In the detection process of the rectification detection circuit 22 that multiplies the rectangular wave, the noise component is also detected and output. As a result, there is a problem that the accuracy of the angular velocity signal S03 is lowered due to the influence of noise.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a physical quantity sensor that is less affected by reference voltage errors and external vibrations and can improve accuracy.

  The physical quantity sensor according to the present invention includes a sensor unit that detects a target physical quantity with a detection sensitivity corresponding to the excitation intensity and outputs a detection signal in an excited state determined by a reference signal, and excites the sensor unit by an oscillation signal. A drive circuit that drives, and a detection circuit that synchronously detects the detection signal with the oscillation signal by a synchronous detection circuit, and generates an output signal corresponding to the target physical quantity from a detection output, the synchronous detection circuit, A current signal Ix corresponding to the detection signal, a current signal Iy corresponding to the oscillation signal, and a reference current Iref corresponding to the reference signal are input, and a current signal Iout corresponding to (Ix · Iy / Iref) is generated. A detection circuit is provided based on the current signal Iout.

  In another physical quantity sensor according to the present invention, the drive circuit includes an amplification unit that receives a reference voltage and controls the amplitude of the oscillation signal to a magnitude corresponding to the reference voltage, and the detection circuit includes: A voltage-current conversion circuit configured to convert the reference voltage into the reference current Iref according to the magnitude of the reference voltage;

  In another physical quantity sensor according to the present invention, the drive circuit includes an amplifying unit that receives a reference voltage as a reference signal and controls the amplitude of the oscillation signal to a magnitude corresponding to the reference voltage. The circuit includes a voltage-current conversion circuit that converts the reference voltage into the reference current Iref corresponding to the magnitude of the reference voltage.

  In the physical quantity sensor according to the present invention, the translinear circuit is a loop that traces the first to third input transistors, one output transistor, and the bases and emitters of the four transistors. Forming a translinear loop in which the direction of the diode formed by the base-emitter junction of the transistor is reversed between the first and second input transistors, the third input transistor, and the output transistor. Connecting means, connected to the collectors or emitters of the first, second and third input transistors, supplying a current corresponding to the current Ix to the first input transistor, and supplying the second input transistor with the current A current corresponding to the current Iy is supplied, and the third input transistor is responded to the current Iref. Current input means for supplying a current with a current output unit to retrieve the current generated in the collector of the output transistor as the current signal Iout, it can be configured to have.

  In the physical quantity sensor according to the present invention, the translinear circuit is a loop that traces the first to third input transistors, one output transistor, and the bases and emitters of the four transistors. An electrical circuit that forms a translinear loop in which the direction of the diode formed by the base-emitter junction of the transistor is reversed between the first and second input transistors, the third input transistor, and the output transistor. And a second connection transistor connected to the collector or emitter of the first, second and third input transistors, supplying a current corresponding to a current (Ix + Iref) to the first input transistor, Current corresponding to the current (Iy + Iref) is supplied to the third input transistor. Current input means for supplying a current corresponding to the current Iref, and current output means for taking out the current generated at the collector of the output transistor and combining it with the current (Ix + Iy + Iref) to produce the current signal Iout. be able to.

  Furthermore, in the physical quantity sensor according to the present invention, the translinear circuit is a loop that traces the first to third input transistors, one output transistor, and the bases and emitters of the four transistors. An electrical circuit that forms a translinear loop in which the direction of the diode formed by the base-emitter junction of the transistor is reversed between the first and second input transistors, the third input transistor, and the output transistor. And connecting to the emitters of the first, second and third input transistors, supplying a current corresponding to the current Ix to the first input transistor, and supplying the current to the second input transistor. A current corresponding to Iy is supplied, and a current corresponding to the current Iref is supplied to the third input transistor. Current input means for supplying the output transistor, adjusting means connected to the emitter of the output transistor for adjusting the current and potential generated in the emitter in response to a control signal, and the current generated in the emitter of the output transistor for the current signal Iout A current output means for taking out the output of the transistor, the connection means having an input terminal on the translinear loop, the emitter of the transistor having a forward direction of the diode, and the emitter of the transistor having a reverse direction; And an output terminal connected to the adjusting means, and an operational amplifier that balances the potential between the emitters by a virtual short circuit.

  In the physical quantity sensor according to the present invention, the translinear circuit is a loop that traces the first to third input transistors, one output transistor, and the bases and emitters of the four transistors. An electrical circuit that forms a translinear loop in which the direction of the diode formed by the base-emitter junction of the transistor is reversed between the first and second input transistors, the third input transistor, and the output transistor. A connection means, connected to the emitters of the first, second, and third input transistors, supplying a current corresponding to a current (Ix + Iref) to the first input transistor, and supplying a current to the second input transistor. A current corresponding to (Iy + Iref) is supplied, and the current Iref is supplied to the third input transistor. Current input means for supplying a corresponding current; adjusting means connected to the emitter of the output transistor for adjusting the current and potential generated in the emitter according to a control signal; and the adjusting means for the emitter of the output transistor; Current supply means connected in parallel and supplying current according to current (Ix + Iy); and current output means for taking out the current flowing through the adjusting means and combining the current Iref with the current signal Iout. The connection means has an input terminal connected to the emitter of the transistor in which the direction of the diode is a positive direction and an emitter of the transistor in the reverse direction on the translinear loop, and an output terminal connected to the output terminal. It can be configured to have an operational amplifier connected to the adjusting means to balance the potential between the emitters by a virtual short circuit.

  The physical quantity sensor according to the present invention detects the detection signal by multiplying the detection signal of the sensor unit by an oscillation signal instead of a rectangular wave, so that it is difficult to detect noise due to external vibration, and the sensitivity of the output signal remains proportional to the reference voltage Vref. Therefore, it is less susceptible to the error of the reference voltage than the detection using the conventional oscillation signal. Therefore, according to the present invention, it is possible to improve the accuracy of the physical quantity sensor that detects the physical quantity according to the vibration.

1 is a schematic block configuration diagram of a vibration gyroscope that is a physical quantity sensor according to an embodiment of the present invention. FIG. 3 is a schematic circuit diagram schematically illustrating a configuration example of an AGC unit. 1 is a schematic block configuration diagram of a synchronous detection circuit in an embodiment of the present invention. It is a circuit diagram which shows the basic composition of an example of the translinear circuit used for a synchronous detection circuit. FIG. 5 is a circuit diagram showing a configuration in which the translinear circuit shown in FIG. 4 can operate in four quadrants. It is typical sectional drawing which shows the structure of the bipolar transistor formed in an n-type semiconductor substrate using a CMOS process. It is a circuit diagram which shows the basic composition of the other example of the translinear circuit used for a synchronous detection circuit. FIG. 8 is a circuit diagram showing a configuration in which the translinear circuit shown in FIG. 7 can operate in four quadrants. FIG. 9 is a circuit diagram showing a modification of the translinear circuit shown in FIGS. 7 and 8. It is a block block diagram of the vibration type gyroscope explaining the conventional synchronous detection system. It is a block block diagram of the vibration type gyroscope explaining the other conventional synchronous detection system.

  Hereinafter, embodiments of the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings.

  FIG. 1 is a schematic block diagram of a vibration gyroscope 30 that is a physical quantity sensor according to the embodiment. The gyroscope 30 includes a sensor element 32, a drive circuit 34, and a detection circuit 36.

  The sensor element 32 includes a vibrator 40 made of a piezoelectric material such as quartz, drive electrodes 42 and 44 paired with each other, and detection electrodes 46 and 48 paired with each other. The drive electrodes 42 and 44 apply the oscillation signal from the drive circuit 34 to the vibrator 40 and excite the vibrator 40 by the inverse piezoelectric effect. When an angular velocity is applied to the excited vibrator 40, the vibrator 40 vibrates due to Coriolis force and generates electric charges due to the piezoelectric effect. The detection electrodes 46 and 48 take out the electric charge generated by the vibration as a current and output it to the detection circuit 36.

  The drive circuit 34 includes a current-voltage conversion circuit (hereinafter referred to as an I / V conversion circuit) 50 and an amplifier 52, and forms a feedback oscillation circuit together with the vibrator 40 to generate a drive signal that is an oscillation signal having a predetermined frequency. The drive circuit 34 applies the drive signal S1 to the drive electrode 42 of the vibrator 40, monitors the current flowing out of the drive electrode 44 according to the vibration of the vibrator 40, and feedback-controls the amplitude of the drive signal.

  The I / V conversion circuit 50 receives the feedback current S2 flowing out from the drive electrode 44, performs current-voltage conversion, and outputs it to the amplifier 52 as a feedback signal S3.

  The amplifying unit 52 includes a variable gain amplifying circuit 54 and an automatic gain control (AGC) unit 56.

  The AGC unit 56 generates a DC monitor voltage Vi corresponding to the amplitude of the feedback signal S3, and based on the monitor voltage Vi and the reference signal, the gain of the variable gain amplifier circuit 54 is adjusted so as to stabilize the excitation level of the oscillation circuit. A signal S4 to be controlled is generated. The AGC unit 56 of the present embodiment uses the reference voltage Vref input from the reference voltage generation circuit 58 as a reference signal, and generates a signal S4 based on the difference between the monitor voltage Vi and the reference voltage Vref. Note that a current signal may be used as the reference signal. In this case, the current signal can be used as a reference current Iref corresponding to the amplitude of the oscillation signal by the synchronous detection circuit 72 described later.

  The gain of the variable gain amplifier circuit 54 is controlled by the control signal S4 from the AGC unit 56, and amplifies the feedback signal S3 with the gain.

  The detection circuit 36 includes a detection amplification unit 70, a synchronous detection circuit 72, an amplification circuit 74, and an LPF 76. The detection circuit 36 processes the detection signals S5 and S6 output from the sensor element 32 to obtain an angular velocity that is a physical quantity to be detected. A corresponding output signal is generated.

  The detection amplification unit 70 is connected to the detection electrodes 46 and 48, and converts the detection signals S5 and S6 input from them into voltage values, respectively. The detection amplification unit 70 includes a differential amplification circuit, and performs differential amplification on the detection signals S5 and S6 converted into voltages.

  The synchronous detection circuit 72 receives the output signal S7 (amplified signal X) of the detection amplification unit 70, performs synchronous detection based on the oscillation signal Y of the drive circuit 34, and generates a detection output S8. In the present embodiment, the feedback signal S3 output from the I / V conversion circuit 50 is used as the oscillation signal Y of the drive circuit 34, and the phase of the signal S3 is adjusted and input to the synchronous detection circuit 72. The synchronous detection circuit 72 uses the reference voltage Vref input from the reference voltage generation circuit 58, as will be described later.

  The amplifier circuit 74 amplifies and outputs the detection output S8 of the synchronous detection circuit 72. The LPF 76 cuts high frequency components from the output signal of the amplifier circuit 74, extracts an angular velocity output S 9 that is an electrical signal corresponding to the angular velocity applied to the vibrator 40, and outputs it from the output terminal 78.

  The drive circuit 34 and the detection circuit 36 are formed as an IC using a silicon substrate or the like. In the IC, in addition to the output terminal 78 described above, terminals (or pads) 80 and 82 for connecting the drive circuit 34 to the drive electrodes 42 and 44 and the detection circuit 36 are connected to the detection electrodes 46 and 48. Terminals (or pads) 84 and 86 are provided. A control terminal 88 for inputting the reference voltage Vref is also provided.

  The reference voltage generation circuit 58 receives a voltage supply from the power supply voltage and generates a reference voltage Vref that does not depend on the power supply voltage.

FIG. 2 is a schematic schematic circuit diagram showing a configuration example of the AGC unit 56. The AGC unit 56 includes an effective value circuit 100 and a control voltage generation circuit 102. The effective value circuit 100 receives the feedback signal S3 and generates an effective value voltage of the feedback signal S3 as a DC monitor voltage Vi corresponding to the amplitude. The control voltage generation circuit 102 generates a control signal S4 based on the difference between the monitor voltage Vi and the reference voltage Vref. The control voltage generation circuit 102 includes, for example, an inverting amplifier circuit using an operational amplifier 104. The inverting input terminal (−) of the operational amplifier 104 is connected to the input resistance Ri between the rms value circuit 100, the feedback resistance Rf is connected to the output terminal of the operational amplifier 104, and the reference voltage Vref is input. A resistor Rref is connected between the terminals. The non-inverting input terminal (+) of the operational amplifier 104 is grounded. When the voltage of the control signal S4 output from the output terminal of the operational amplifier 104 is expressed as Vo, the following equation is established from Kirchhoff's current conservation law at the inverting input terminal (−).
Vi / Ri + Vref / Rref = -Vo / Rf (1)

  Usually, Rf is sufficiently larger than Ri and Rref, so that if the right side of equation (1) is regarded as 0, equation (1) indicates that monitor voltage Vi indicating the excitation level is substantially proportional to | Vref |. This indicates that the excitation level of the oscillation circuit is set with reference to Vref.

  Note that when the reference current (Iref) is used as the reference signal, the control voltage generation circuit 102 is configured such that the reference voltage Vref is connected to the inverting input terminal (−) of the operational amplifier 104 shown in FIG. Instead of the applied configuration, the reference current Iref is supplied to the inverting input terminal (−). Iref is supplied in the direction of drawing from the inverting input terminal (−), and is configured to cancel the current flowing from the effective value circuit 100 to the inverting input terminal (−).

  As described above, the reference voltage generation circuit 58 is designed to keep the reference voltage Vref constant, but in reality, the Vref changes due to variations in temperature and power supply voltage, aging of the circuit, and the like. This change in the reference voltage Vref changes the signal level of the drive signal, the signal levels of the detection signals S5 and S6 of the sensor element 32 change accordingly, and further the signal level of the angular velocity output S9 changes. The synchronous detection circuit 72 of this embodiment reduces the fluctuation of the angular velocity output S9 caused by the fluctuation of the reference signal such as the reference voltage Vref and the reference current that should be the reference signal.

  FIG. 3 is a schematic block diagram of the synchronous detection circuit 72. The synchronous detection circuit 72 includes voltage-current conversion circuits (hereinafter referred to as V / I conversion circuits) 110a, 110b, and 110c, a translinear circuit 112, and an I / V conversion circuit 114.

  As already described, the synchronous detection circuit 72 is supplied with the amplified signal X from the detection amplifier 70, the oscillation signal Y from the drive circuit 34, and the reference voltage Vref from the reference voltage generation circuit 58. The V / I conversion circuits 110a, 110b, and 110c receive signals X, Y, and Vref, respectively, convert the voltage signals X, Y, and Vref into current signals Ix, Iy, and Iref, and input them to the translinear circuit 112.

  The translinear circuit 112 is an analog circuit using the translinear principle. The translinear principle is the number of semiconductor junctions having a polarity in the clockwise direction (CW) and the semiconductor junction having a polarity in the counterclockwise direction (CCW) in a loop coupled so as to go around the base and emitter of a plurality of transistors. Are equal, the product of the collector current of the transistor in which the base current flows in the clockwise direction is equal to the product of the collector current of the transistor in which the base current flows in the counterclockwise direction.

A translinear circuit can perform multiplication, division, etc. using an analog signal. The translinear circuit 112 of this embodiment receives a current signal Ix corresponding to the detection signal of the sensor element 32, a current signal Iy corresponding to the oscillation signal of the drive circuit 34, and a reference current Iref corresponding to the amplitude of the oscillation signal, An output current Iout expressed by the following equation is generated and output.
Iout = Ix · Iy / Iref (2)

  The I / V conversion circuit 114 converts the output current Iout of the translinear circuit 112 into a voltage signal Vout and outputs the voltage signal Vout to the amplifier circuit 74 as a detection output S8.

FIG. 4 is a schematic circuit diagram showing an example of the translinear circuit 112. The translinear circuit 112 operates by being supplied with power sources V ₊ and V ₋ . The potentials of these power sources are V ₊ > V ₋ . The translinear circuit 112 has a translinear loop composed of four transistors Q1 to Q4. In the configuration of FIG. 4, the transistors Q1 to Q3 are input transistors to which an input current is supplied from the outside of the translinear circuit 112, and Q4 is an output transistor that generates an output current. In this example, each transistor is an npn type. The emitters of the transistors Q1 and Q3 are connected to current sources I1 and I3 that supply currents Ix and Iref, respectively. The emitter of the transistor Q2, Q4 power V _- is connected to. The collectors of Q1 and Q3 are connected to a power source V _+, and the collector of Q2 is connected to a current source I2 that supplies a current Iy. The collector of Q4 is connected to the input terminal of the I / V conversion circuit 114. The current flowing through Q4 is defined as Iout. Further, the bases of Q1 and Q3 are both connected to the power source V ₊ , the emitter of Q1 and the base of Q2 are connected, the emitter of Q3 and the base of Q4 are connected, and the emitter of Q2 and the emitter of Q4 are already described. both power V as _- is connected to, translinear loop is formed by the connection of the base and emitter. In this loop, the direction of the base-emitter junction is opposite between the pair of Q1 and Q2 and the pair of Q3 and Q4. Therefore, the above equation (2) is established based on the translinear principle.

  As described with reference to the multiplication circuit 14 of the conventional gyroscope 2 in FIG. 10, the product (Ix · Iy) is proportional to the square of Vref, but the synchronous detection circuit 72 of this embodiment uses the translinear circuit 112. The result of dividing by Iref proportional to Vref is taken out as Iout. That is, Iout is simply proportional to Vref (ie, to the first power). Therefore, the angular velocity output S9 obtained based on this Iout is less affected by the error of the reference voltage Vref than the angular velocity output by the synchronous detection using the multiplication circuit 14 of FIG.

  The current Iy multiplied by the current signal Ix in the translinear circuit 112 is a signal that changes according to the waveform of the oscillation signal. That is, Iy is basically a waveform corresponding to the sine wave of the fundamental vibration mode, and the synchronous detection circuit 72 is difficult to detect the higher-order vibration mode component, so that the angular velocity output S9 is not easily affected by external vibration.

  As described above, the synchronous detection circuit 72 using the translinear circuit 112 can reduce the influence of the error of the reference voltage Vref and reduce the noise due to the higher-order vibration mode, so that the accuracy of the angular velocity output can be improved.

  Actually, the synchronous detection circuit 72 is configured to be operable in four quadrants. That is, regardless of the signs of the amplified signal X and the oscillation signal Y, the directions of the collector currents of the transistors Q1 and Q2 are fixed, and the synchronous detection circuit 72 is always operated regardless of the phases of the signals X and Y.

  FIG. 5 is a circuit diagram showing a configuration in which the translinear circuit 112 shown in FIG. 4 can operate in four quadrants. The circuit configuration of the translinear loop of the translinear circuit 112 shown in FIG. 5 is the same as that shown in FIG. 4, and the difference from the configuration shown in FIG. 4 is the input generated by the V / I conversion circuits 110a to 110c. The current Ix, Iy, Iref is input to the translinear circuit 112, and the current Iout is output to the I / V conversion circuit 114. The current source I1 connected to the emitter of Q1 supplies (Ix + Iref), and the current source I2 connected to the collector of Q2 supplies (Iy + Iref). In order to perform the four-quadrant operation, Iref is set so that (Ix + Iref)> 0 and (Iy + Iref)> 0. A current source I3 connected to the emitter of Q3 supplies Iref as in FIG. The input currents (Ix + Iref), (Iy + Iref) and Iref are generated using the output currents of the V / I conversion circuits 110a to 110c, and are replicated at the positions of the current sources I1 to I3 using, for example, a current mirror circuit.

When the collector current of Q4 is expressed as Iη, the following equation is established by the translinear principle.
(Ix + Iref) · (Iy + Iref) = Iη · Iref (3)

The following equation is derived from the equations (2) and (3).
Iη = Iout + Ix + Iy + Iref (4)

  That is, Iη is a current obtained by superimposing a current (Ix + Iy + Iref) on Iout expressed by the equation (2). Therefore, the collector of Q4 that draws the current Iη and the current source I4 that supplies the current (Ix + Iy + Iref) are connected to the I / V conversion circuit 114. As a result, the superimposed current (Ix + Iy + Iref) is canceled from Iη at the input terminal of the I / V conversion circuit 114, and a voltage signal Vout corresponding to Iout is obtained at the output terminal of the I / V conversion circuit 114. Therefore, with the configuration of FIG. 5, the synchronous detection circuit 72 having the effects of the present invention described with reference to the circuit of FIG. 4 can be realized.

  Next, another example of the translinear circuit 112 will be described. The translinear circuit 112 in this example has a configuration suitable for manufacturing an IC constituting the detection circuit 36 by a CMOS process. In this configuration, the bipolar transistor that constitutes the translinear circuit 112 is formed by a CMOS process.

FIG. 6 is a schematic view showing the structure of the bipolar transistor, and shows a cross section perpendicular to the semiconductor substrate. FIG. 6 shows an example in which the semiconductor substrate for forming the IC is an n-type substrate (hereinafter referred to as n-sub) 200 to which n-type impurities are introduced and n-type conductivity (first conductivity type) is given. Yes. A p-type well (p-well) 202, which is a semiconductor region made of p-type conductivity (second conductivity type), is formed on the surface of the n-sub 200 by introducing p-type impurities. Further, an n-type region 204 is formed in the p well 202. As a result, an npn-type transistor having the n-sub 200 as the collector (C), the p-well 202 as the base (B), and the n-type region 204 as the emitter (E) is formed. Incidentally, in the CMOS process, the p-well 202 is formed by a step of forming a region that becomes a channel of the n-type MOS transistor. Specifically, a mask having an opening in the region where the p-well 202 is formed is formed of a photoresist or the like. It is formed by ion implantation and thermal diffusion of p-type impurities. The n-type region 204 is formed by a process of forming the source and drain diffusion layer regions of the n-channel MOS transistor. Specifically, after forming a mask, the n-type region 204 is formed by ion implantation of n-type impurities. In the bipolar transistor formed by this CMOS process, the collector is fixed at the substrate potential Vsub. For an n-type substrate, Vsub can be a positive potential V ₊ .

  FIG. 7 is a circuit diagram showing a basic configuration of an example of the translinear circuit 112 using the above-described bipolar transistor manufactured by a CMOS process. This translinear circuit 112 has a translinear loop composed of four transistors Q1 to Q4 as in the configuration of FIG. The collectors of the transistors Q1 to Q4 are the n-sub 200 as described above, and are set to the common potential Vsub. For this reason, the collectors of the transistors Q1 to Q4 cannot be used for supply of input current or extraction of output current, and thus there is a restriction that is not included in the configuration of FIG.

The translinear circuit 112 has current sources I1 to I3 as current supply means for supplying an input current to the emitters of the transistors Q1 to Q3. In the circuit shown in FIG. 7, current sources I1-I3 supply currents Ix, Iy, Iref to the emitters of transistors Q1-Q3 using output currents of V / I conversion circuits 110a, 110b, 110c, respectively. Here, the current sources I1 to I3 supply the input current from the base to the emitter. For example, when the current Iref generated by the V / I conversion circuit 110c is directed to flow into the V / I conversion circuit 110c, the output terminal of the V / I conversion circuit 110c is connected to the emitter of Q3 as the current source I3. Good. On the other hand, when Iref is oriented flowing from V / I conversion circuit 110c is the current example, by using a current mirror circuit, Q3 the emitter and the power supply V in predetermined negative voltage _- to replicate path connecting the . The other input currents Ix and Iy are similarly configured.

  Translinear circuit 112 takes out the current generated at the emitter of transistor Q4 as output current Iout. Iout is input to the I / V conversion circuit 114.

  The bases of Q1 and Q3 are connected to the n-sub 200, the emitter of Q1 and the base of Q2 are connected by, for example, wiring formed on the substrate, and the emitter of Q3 and the base of Q4 are similarly connected by wiring. Here, in order to complete the transformer loop, the emitter of Q2 and the emitter of Q4 need to be connected to have the same potential. However, since the emitter of Q2 is connected to the current supply means for supplying the input current Iy and the emitter of Q4 is connected to the current output means for taking out the output current Iout, it is not possible to simply connect the emitters of Q2 and Q4. . The translinear circuit 112 is configured by a circuit using an operational amplifier 210 as a connecting means for this portion.

Specifically, the operational amplifier 210 has an inverting input terminal (−) connected to the emitter of Q2, and a non-inverting input terminal (+) connected to the emitter of Q4. Further, the n-channel MOS transistor M1 emitter and the power supply V of Q4 _- connected between the. M1 is the drain to the emitter of Q4, also the source power V _- is connected to and a gate connected to an output terminal of the operational amplifier 210. The operational amplifier 210 virtually short-circuits the emitters of Q2 and Q4 to balance the potential, and controls M1 to set the emitter potential of Q4 so that the above equation (2) is established for the translinear loop. The current Iout flowing out from the emitter of Q4 and flowing between the drain and source of M1 is duplicated by the n-channel MOS transistor M2 whose gate potential is controlled in the same manner as M1 by the output voltage of the operational amplifier 210. M2 is the source power V _- is connected to, and a drain connected to the I / V conversion circuit 114. The I / V conversion circuit 114 converts the duplicated Iout into a voltage signal Vout and outputs it as a detection output S8 to the amplification circuit 74.

  FIG. 8 is a circuit diagram showing a configuration in which the translinear circuit 112 shown in FIG. 7 can operate in four quadrants. 5 is different from the circuit of FIG. 7 in that the circuit of FIG. 8 is different from the circuit of FIG. 4 in that the translinear circuit of the input currents Ix, Iy, and Iref generated by the V / I conversion circuits 110a to 110c. 112 and a method of outputting a current Iout to the I / V conversion circuit 114. The current source I1 connected to the emitter of Q1 supplies (Ix + Iref), and the current source I2 connected to the collector of Q2 supplies (Iy + Iref). In order to perform the four-quadrant operation, Iref is set so that (Ix + Iref)> 0 and (Iy + Iref)> 0. A current source I3 connected to the emitter of Q3 supplies Iref as in FIG. The input currents (Ix + Iref), (Iy + Iref) and Iref are generated using the output currents of the V / I conversion circuits 110a to 110c, and are replicated at the positions of the current sources I1 to I3 using, for example, a current mirror circuit. In this circuit, the equation (4) is established for the collector current Iη of Q4, as in the circuit of FIG.

Q3 emitter and power source V _- current source I5 in parallel to the transistor M1 is connected between the. The current source I5 supplies a current (Ix + Iy) to the emitter of the transistor Q4. Similarly to the current sources I1 to I3, the current source I5 supplies a current from the base of Q4 toward the emitter. Thus, M1 is controlled by the operational amplifier 210 so that a current (Iout + Iref) flows. Note that by adding Iref, (Iout + Iref)> 0 can be established, and a current that changes in accordance with Iout flows through M1 regardless of the polarity of Iout, thereby enabling a four-quadrant operation. The current of M1 is duplicated in M2, and M2 draws the current (Iout + Iref) from the input terminal of the I / V conversion circuit 114. In addition to the transistor M2, the input terminal of the I / V conversion circuit 114 is connected to a current source I4 that sends a current Iref to the input terminal. The I / V conversion circuit 114 receives a current Iout obtained by combining the current from the transistor M2 and the current from the current source I4, and outputs a voltage signal Vout corresponding to Iout to its output terminal.

  Here, a transistor for obtaining an output current can be freely selected from a group of transistors constituting the translinear loop. For example, in the circuit configurations of FIGS. 7 and 8, the input current is supplied to Q1 to Q3 and the output current is extracted from Q4. However, the output current can be extracted from Q3 among Q1 to Q4 of the circuit. . FIG. 9 is a circuit diagram of the translinear circuit 112 having the configuration described above, and shows a configuration capable of four-quadrant operation as in the configuration of FIG. In the circuit of FIG. 9, the current source I5 and the transistor M1 connected to the emitter of Q4 in the circuit of FIG. 8 are connected to the emitter of Q3, and the current source connected to the emitter of Q3 in the circuit of FIG. I3 is connected to the emitter of Q4. Also in this circuit, the operational amplifier 210 connected between the emitters of Q2 and Q4 sets the emitters at the same potential and controls M1 so that the translinear principle in the translinear loop completed thereby is established. To do. Therefore, Equation (4) is established for the collector current Iη of Q3, and Vout can be obtained from the I / V conversion circuit 114 in the same manner as the circuit of FIG.

  As described above, the synchronous detection circuit 72 having the effects of the present invention described with reference to the circuit of FIG. 4 can also be realized by the configurations of FIGS.

  In addition, this invention is not limited to embodiment mentioned above, A various deformation | transformation is possible. For example, the translinear circuit 112 in FIGS. 7 to 9 has been described using an npn transistor formed on an n-type substrate. Similarly, a pnp transistor is formed on a p-type substrate using a CMOS process. The translinear circuit 112 can be formed using the pnp transistor.

  The above-described embodiment is a vibrating gyroscope that is driven by the piezoelectric effect and detects an angular velocity. However, the present invention can also be applied to a vibrating gyroscope of another driving method. The physical quantity to be detected by the physical quantity sensor according to the present invention is not limited to the angular velocity, and the present invention can be applied to, for example, a vibration type acceleration sensor.

  30 gyroscope, 32 sensor element, 34 drive circuit, 36 detection circuit, 40 transducer, 42, 44 drive electrode, 46, 48 detection electrode, 50, 114 I / V conversion circuit, 52 amplification unit, 54 variable gain amplification circuit , 56 AGC section, 58 reference voltage generation circuit, 70 detection amplification section, 72 synchronous detection circuit, 74 amplification circuit, 76 LPF, 78 output terminal, 88 control terminal, 100 RMS circuit, 102 control voltage generation circuit, 104, 210 Operational amplifier, 110a, 110b, 110c V / I conversion circuit, 112 translinear circuit, 200 n-type substrate, 202 p-well, 204 n-type region.

Claims (6)

A sensor unit that detects a target physical quantity with a detection sensitivity corresponding to the excitation intensity and outputs a detection signal in an excited state determined by a reference signal;
A drive circuit for exciting and driving the sensor unit by an oscillation signal;
A detection circuit that synchronously detects the detection signal with the oscillation signal by a synchronous detection circuit, and generates an output signal corresponding to the target physical quantity from a detection output;
Have
The synchronous detection circuit receives a current signal Ix corresponding to the detection signal, a current signal Iy corresponding to the oscillation signal, and a reference current Iref corresponding to the reference signal, and a current corresponding to (Ix · Iy / Iref) A physical quantity sensor having a translinear circuit for generating a signal Iout and obtaining the detection output based on the current signal Iout. The physical quantity sensor according to claim 1,
The drive circuit has an amplification unit that receives a reference voltage as a reference signal and controls the amplitude of the oscillation signal to a magnitude according to the reference voltage;
The detection circuit includes a voltage-current conversion circuit that converts the reference voltage into the reference current Iref according to the magnitude thereof;
A physical quantity sensor characterized by The physical quantity sensor according to claim 1 or 2,
The translinear circuit is:
First to third input transistors and one output transistor;
A loop that follows the base and emitter of the four transistors, the direction of the diode formed by the base-emitter junction of the transistor on the loop being the first and second input transistors and the third input transistor; And an electrical connection means for forming a translinear loop that is opposite to the output transistor,
Connected to the collectors or emitters of the first, second, and third input transistors, supplies a current corresponding to the current Ix to the first input transistor, and responds to the current Iy to the second input transistor. Current input means for supplying a current corresponding to the current Iref to the third input transistor;
Current output means for extracting the current generated at the collector of the output transistor as the current signal Iout;
A physical quantity sensor comprising: The physical quantity sensor according to claim 1 or 2,
The translinear circuit is:
First to third input transistors and one output transistor;
A loop that follows the base and emitter of the four transistors, the direction of the diode formed by the base-emitter junction of the transistor on the loop being the first and second input transistors and the third input transistor; And an electrical connection means for forming a translinear loop that is opposite to the output transistor,
Connected to the collectors or emitters of the first, second, and third input transistors, supplies a current corresponding to a current (Ix + Iref) to the first input transistor, and supplies a current (Iy + Iref) to the second input transistor. Current input means for supplying a current corresponding to the current Iref and supplying a current corresponding to the current Iref to the third input transistor;
Current output means for taking out a current generated at the collector of the output transistor and combining it with a current (Ix + Iy + Iref) as the current signal Iout;
A physical quantity sensor comprising: The physical quantity sensor according to claim 1 or 2,
The translinear circuit is:
First to third input transistors and one output transistor;
A loop that follows the base and emitter of the four transistors, the direction of the diode formed by the base-emitter junction of the transistor on the loop being the first and second input transistors and the third input transistor; And an electrical connection means for forming a translinear loop that is opposite to the output transistor,
A current connected to the emitters of the first, second and third input transistors, supplying a current corresponding to the current Ix to the first input transistor, and a current corresponding to the current Iy to the second input transistor. Current input means for supplying current corresponding to the current Iref to the third input transistor;
Adjusting means connected to the emitter of the output transistor for adjusting the current and potential generated in the emitter in response to a control signal;
Current output means for taking out the current generated in the emitter of the output transistor as the current signal Iout;
Have
The connection means has an input terminal connected to the emitter of the transistor whose forward direction is the diode on the translinear loop and an emitter of the transistor whose reverse direction is the reverse direction, and an output terminal which is the adjustment means. An operational amplifier that is connected to the emitter and balances the potential between the emitters by a virtual short circuit,
A physical quantity sensor characterized by The physical quantity sensor according to claim 1 or 2,
The translinear circuit is:
First to third input transistors and one output transistor;
A loop that follows the base and emitter of the four transistors, the direction of the diode formed by the base-emitter junction of the transistor on the loop being the first and second input transistors and the third input transistor; And an electrical connection means for forming a translinear loop that is opposite to the output transistor,
Connected to the emitters of the first, second, and third input transistors, supplies a current corresponding to a current (Ix + Iref) to the first input transistor, and responds to a current (Iy + Iref) to the second input transistor. Current input means for supplying a current corresponding to the current Iref to the third input transistor;
Adjusting means connected to the emitter of the output transistor for adjusting the current and potential generated in the emitter in response to a control signal;
Current supply means connected in parallel to the adjusting means to the emitter of the output transistor and for supplying a current according to the current (Ix + Iy);
A current output means for taking out a current flowing through the adjusting means and combining the current Iref with the current signal Iout;
Have
The connection means has an input terminal connected to the emitter of the transistor whose forward direction is the diode on the translinear loop and an emitter of the transistor whose reverse direction is the reverse direction, and an output terminal which is the adjustment means. An operational amplifier that is connected to the emitter and balances the potential between the emitters by a virtual short circuit,
A physical quantity sensor characterized by

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