JP5119826B2 - Compensation voltage circuit and temperature compensated piezoelectric oscillator - Google Patents

Description

  The present invention relates to a compensation voltage circuit and a temperature compensation type piezoelectric oscillator, and relates to a temperature compensation type in which an output voltage of the compensation voltage circuit changes smoothly with respect to a temperature change and a rapid frequency fluctuation (dip) occurring in an oscillation frequency is suppressed. The present invention relates to a piezoelectric oscillator.

In recent years, piezoelectric oscillators are used in many fields from communication devices such as mobile phones to consumer devices such as quartz watches because of their frequency stability, small size and light weight, and low price. In particular, a temperature compensated piezoelectric oscillator (TCXO) that compensates for the frequency temperature characteristics of a piezoelectric vibrator is widely used in mobile phones and the like that require frequency stability.
Patent Document 1 discloses a temperature compensated crystal oscillator including a function generation circuit. FIG. 10 is a functional block diagram of the temperature-compensated crystal oscillator, which includes a constant voltage circuit 32, a temperature sensor circuit 33, a control circuit 34 that generates a control voltage Vc to compensate for the temperature characteristics of the crystal resonator, In order to optimize the oscillation frequency output from the VCXO 35 with respect to the control voltage Vc output from the control crystal oscillator (VCXO) 35 and the control circuit 34, a ROM / stores temperature compensation parameters for compensating the temperature characteristics of the control voltage Vc. And a RAM circuit 36.
The control circuit 34 includes a MAX circuit 34a and a MIN circuit 34b. When the control voltage y1, the control voltage y2, and the control voltage y3 generated by the constant voltage circuit 32 and the temperature sensor circuit 33 are input to the control circuit 34a, the maximum voltage value is selected and output as the control voltage y6. . Similarly, when the control voltage y4 and the control voltage y5 generated similarly and the control voltage y6 from the MAX circuit 34a are input to the control circuit 34b, the minimum voltage value is selected and the control voltage y7 is output. This control voltage y7 becomes the temperature compensation control voltage Vc.

  FIG. 11 is a diagram showing details of the control voltage Vc. FIG. 11 shows the control voltage y1 in the first temperature region (T0 ≦ Ta ≦ T1), the control voltage y2 in the second temperature region (T1 ≦ Ta ≦ T2), and the third temperature region (T2 ≦ Ta ≦ T3). , The control voltage y3 in the fourth temperature region (T3 ≦ Ta ≦ T4), and the control voltage y5 in the fifth temperature region (T4 ≦ Ta ≦ T5), respectively. The control voltage Vc is a broken line represented by a thick solid line. When this control voltage Vc is applied to the voltage controlled crystal oscillator 35, a temperature compensated crystal oscillator is configured. Although not shown, the ROM / RAM circuit 36 receives a RAM data input circuit as a serial data input unit composed of four flip-flops connected in series, and output data of the RAM data input circuit. It has four PROM circuits for storing each bit and control signals (SEL, W / R, DATA, etc.).

  Patent Document 2 discloses a temperature compensated piezoelectric oscillator 50 including a clip voltage generation circuit that clips a temperature compensated voltage to a predetermined voltage. FIG. 12 is a diagram showing a circuit configuration of the temperature-compensated piezoelectric oscillator 50, which includes an oscillation circuit 52 and a frequency temperature compensation circuit 51 that compensates for frequency fluctuations of the piezoelectric vibrator due to temperature changes. The frequency temperature compensation circuit 51 includes a temperature detection unit 53, a temperature compensation voltage generation circuit 52 that generates a voltage based on the changed parameter of the temperature detection unit 53, and a temperature compensation voltage output from the temperature compensation voltage generation circuit 52. MOS capacitor elements MH and ML whose capacitance changes based on a potential difference between (VH, VL) and a reference voltage (Vref), and a clip voltage generation circuit 55 that clips the temperature compensation voltage to a predetermined voltage. The

  FIG. 13 is a diagram showing temperature characteristics of the compensation voltage. Consider the case where the temperature rises from low to high. The low-temperature compensation voltage VL is at the intersection R between the VL and the reference voltage Vref when the temperature is low (−40 ° C.), and the voltage between the terminals of the low-temperature MOS capacitor ML at that time is 0V. When the temperature rises, VL decreases linearly, and accordingly, the ML terminal voltage increases and the ML capacity increases. Then, by setting the circuit so that VL becomes lower than the clip voltage Vcl2 of the clip voltage generation circuit 55 at around normal temperature (+ 25 ° C.), the diode D2 of the clip voltage generation circuit 55 near + 25 ° C. is forward biased. Thus, the connection point P becomes the voltage of the clip voltage Vcl2. When the temperature further rises, VL further decreases, but since it is clipped by the clipping voltage Vcl2, it becomes constant as shown in FIG.

Next, consider a case where the temperature drops from a high temperature to a low temperature. The high temperature compensation voltage VH is at the intersection S between VH and the reference voltage Vref when VH is high temperature (+ 90 ° C.). Since the voltage between the terminals of the high-temperature MOS capacitor MH at that time is 0 V, MH is C− The capacitance is in the range of the rise of the V characteristic. When the temperature decreases, VH decreases linearly, and accordingly, the potential difference of the forward bias of MH increases and the capacitance decreases. Then, by setting the circuit so that VH is lower than the clip voltage Vcl2 of the clip voltage generation circuit 55 near + 25 ° C., the diode D1 of the clip voltage generation circuit 55 becomes forward biased, and the connection point Q is set to the clip voltage Vcl2. Voltage. The broken line RPQS is a compensation voltage. This compensation voltage is applied to a compensation circuit composed of a low and high temperature MOS capacitor element ML, MH and a capacitor to constitute a temperature compensated piezoelectric oscillator.
WO99 / 03195 JP 2005-236798 A

However, the function generation circuit, the crystal oscillation device, and the method for adjusting the crystal oscillation device disclosed in Patent Document 1 have a problem that the number of semiconductor elements in the IC circuit is extremely large, resulting in an increase in cost and a decrease in yield. It was. Furthermore, the control voltage output from the function generation circuit is a polygonal line, and the change in the voltage becomes abrupt at the joint between the straight line and the straight line, and the error between the desired control voltage (compensation voltage) and the generated control voltage is different. There was a problem of getting bigger. In addition, when the control voltage changes suddenly with respect to a temperature change, a frequency dip occurs in the output frequency of the crystal oscillation device, and there is a problem that it may adversely affect a device on which the crystal oscillation device is mounted.
Further, the compensation voltage disclosed in Patent Document 2 is also a broken line composed of three straight lines, and the change in voltage is abrupt at the joint between the straight lines and the error between the desired compensation voltage and the generated compensation voltage. There is a problem that a large frequency and a frequency dip (a phenomenon in which the frequency changes rapidly) occur in the output of the temperature compensated piezoelectric oscillator using the above-described polygonal compensation voltage.
The present invention has been made to solve the above-described problem, and provides a compensation voltage circuit and a temperature compensation type piezoelectric oscillator in which a straight line and a straight line are smoothed with a simple circuit configuration and temperature compensation accuracy is improved. is there.

To achieve the above object, a compensation voltage circuit according to the present invention comprises a temperature sensor that senses the ambient temperature, and a compensation voltage generator that generates a compensation voltage according to the temperature detection result of the temperature sensor. The compensation voltage generator includes an operational amplifier that amplifies the output voltage of the temperature sensor and a transistor, and a first terminal and a second terminal of the transistor are respectively an inverting input terminal of the operational amplifier. It is connected to an output terminal.
When the compensation voltage circuit is configured as described above, the compensation voltage characteristic with respect to the temperature becomes a compensation voltage characteristic in which the vicinity of the intersection of the straight line is connected by a smooth curve. When this compensation voltage circuit is applied to a temperature compensated piezoelectric oscillator, the frequency The compensation accuracy is improved, and the frequency dip can be suppressed.

In the compensation voltage circuit of the present invention, a gain adjusting amplifier for adjusting the gain is provided between the temperature sensor and the operational amplifier.
When the compensation voltage circuit is configured in this way, it is possible to raise or lower the slope of the compensation voltage characteristic by changing the gain of the gain adjustment amplifier, and in combination with the gain adjustment of the operational amplifier that changes the slope of the slope, the compensation voltage characteristic Can be approximated to a desired characteristic.
In the compensation voltage circuit of the present invention, a gain adjusting amplifier for adjusting the gain is provided between the temperature sensor and the gate (third terminal) of the transistor.
When the compensation voltage circuit is configured in this way, by changing the gain of the gain adjustment amplifier, it is possible to change the characteristic of the flat part of the compensation voltage characteristic, in particular, monotonically increasing, flat, and monotonically decreasing with respect to temperature. There is an effect that the accuracy of approximation of the voltage characteristic can be improved.

In the compensation voltage circuit according to the present invention, the transistor includes a plurality of transistors connected in parallel, each of the plurality of transistors having a first terminal connected to an inverting input terminal of the operational amplifier, and each of the plurality of transistors having a first terminal. Two terminals are connected to an output terminal of an operational amplifier.
By configuring the compensation voltage circuit in this way, it is possible to finely adjust the curve portion of the compensation voltage characteristic by adjusting the gain of each of the plurality of gain adjustment amplifiers. The voltage characteristic can be brought close to a desired characteristic.
In the compensation voltage circuit of the present invention, the compensation voltage generator further includes a diode, the cathode terminal of the diode is connected to the output line of the operational amplifier, and the reference voltage is applied to the anode terminal of the diode.
By configuring the compensation voltage circuit in this way, there is an advantage that the output voltage of the compensation voltage circuit can be held at the clip voltage determined by the reference voltage.

In the compensation voltage circuit of the present invention, the transistor is an N-channel MOSFET or a P-channel MOSFET.
When the compensation voltage circuit is configured in this way, a compensation voltage characteristic having an inverse characteristic can be configured by using an N-channel MOS FET or a P-channel MOSFET for the compensation voltage circuit. There is an effect that it can be spread.
The compensation voltage circuit of the present invention has two compensation voltage generators, one of the compensation voltage generators being an N-channel MOSFET and the other of the compensation voltage generators being a P-channel MOSFET.
When the compensation voltage circuit is configured in this manner, one compensation voltage circuit can compensate the range from the low temperature to the normal temperature of the piezoelectric vibrator exhibiting a cubic curve, and the other compensation voltage circuit can compensate the range from the normal temperature to the high temperature. There is an effect.
The temperature compensated piezoelectric oscillator of the present invention constitutes a temperature compensated piezoelectric oscillator including the compensation voltage circuit of the present invention.
Constituting a temperature-compensated piezoelectric oscillator in this manner has the effect of improving the compensation accuracy of the oscillation frequency and suppressing the frequency dip.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1A is a diagram showing a configuration of a compensation voltage circuit according to the first embodiment of the present invention.
The compensation voltage circuit 1 includes a temperature sensor 11 that senses the temperature around the piezoelectric vibrator X, and a compensation voltage generator 12 that generates a compensation voltage according to the temperature detection result of the temperature sensor 11. The compensation voltage generator 12 includes, for example, an operational amplifier OP, variable resistors R1 and R2, and a transistor Tr.
As shown in FIG. 1A, the compensation voltage circuit 1 connects the output line of the temperature sensor 10 to the inverting input terminal (−) of the operational amplifier OP via the variable resistor R1 and also supplies the reference voltage V1 to the non-voltage. The voltage is applied to the inverting input terminal (+), and the inverting input terminal of the operational amplifier OP and the output terminal A are connected via the variable resistor R2 (feedback resistor). The reference voltage Vref is applied to the gate terminal (third terminal) of the transistor Tr, the drain terminal (first terminal) is the inverting input terminal of the operational amplifier OP, and the source terminal (second terminal) is the output of the operational amplifier OP. Connect to terminal A. The output voltage Va of the compensation voltage circuit 1 is applied to the variable capacitance element C of the piezoelectric oscillator 10 via the resistor R.

FIG. 1B shows the temperature-output voltage characteristics of the temperature sensor 11, and FIG. 1C shows the output voltage characteristics of the compensation voltage circuit 1 with respect to temperature changes. The operation when the output voltage Vs of the temperature sensor having the characteristics shown in FIG. 1B is applied to the inverting input terminal of the operational amplifier OP through the variable resistor R1 will be described.
First, the operation in the α region in FIG. In this α region, since the output voltage Vs of the temperature sensor 11 is inverted and amplified by the operational amplifier OP as it is, an output corresponding to the α region in FIG. 1B is obtained as the output voltage Va of the operational amplifier OP. . At this time, since the gate voltage V _GATE (= Vref) of the transistor Tr is lower than the source voltage V _SOURCE , the transistor Tr is in an OFF state, and the drain and source of the transistor Tr are in a non-conductive state. Yes.
Here, a supplementary explanation will be given of the operation of the transistor Tr (N-channel MOSFET). Assuming that the voltage between the gate and the source is V _GS , when V _GS is smaller than the constant voltage VT (threshold voltage), the transistor Tr is turned off and the drain and the source are not conductive. On the other hand, if it is large, it will be in the ON state and the drain-source will be conductive. That is, it is known that if V _GS <VT, the transistor Tr is in an OFF state, and if V _GS > VT, the transistor is in an ON state. The threshold voltage VT is a constant voltage unique to the transistor determined by the characteristics of the MOSFET, and is a value determined by the semiconductor manufacturing process.

Next, the operation of the β region shown in FIGS. 1B and 1C will be described. In this β region, V _GS ≈VT, and the source voltage V _SOURCE of the transistor Tr is almost equal to the gate voltage V _GATE (= Vref). This β region is a region where the transistor Tr gradually changes from the OFF state to the ON state, and the source and drain of the transistor Tr gradually change from the non-conductive state to the conductive state. Therefore, the change of the compensation voltage Va becomes a curve and smoothly changes as shown in FIG.
Next, the operation in the γ region of FIGS. 1B and 1C will be described. In this γ region, V _GS > VT, and the transistor Tr is turned on. At this time, since the source-drain of the transistor Tr becomes conductive, even if the output voltage Vs of the temperature sensor 11 increases, V _GS becomes a clipped state at a point slightly exceeding VT, and becomes a substantially constant voltage. .
FIG. 1D shows characteristics of the compensation voltage Va with respect to temperature when the variable resistors R1 and R2 of the compensation voltage circuit 1 are varied and the gain of the operational amplifier OP is adjusted. The tilt changes to rotate. In FIG. 1E, the slope of the compensation voltage Va characteristic can be moved up and down (referred to as reference adjustment) as shown in the figure by changing the reference voltage V1.

FIG. 2 is a diagram illustrating a configuration of the compensation voltage circuit 2 according to the second embodiment. The difference from the compensation voltage circuit 1 in FIG. 1A is that a gain is provided between the temperature sensor 11 and the variable resistor R1. Is an adjustable gain adjusting amplifier AMP. In the compensation voltage circuit 1 shown in FIG. 1 (a), after adjusting the gain of the operational amplifier OP by changing the variable resistors R1 and R2, when the reference voltage V1 is adjusted, the center of rotation of the slope moves, The reference adjustment cannot be performed independently. However, in the compensation voltage circuit 2 shown in FIG. 2, the gain adjustment by the gain adjustment amplifier AMP and the reference adjustment by the reference voltage V1 can be performed independently of each other, so that the rotation center of the inclination of the compensation voltage Va is not moved. There is an advantage that reference adjustment can be performed.
FIG. 3 is a diagram showing the configuration of the compensation voltage circuit 3 according to the third embodiment. The difference from the compensation voltage circuit 1 of FIG. 1A is that the output of the temperature sensor 11 is converted into the gain adjustment amplifier AMP. This is a point connected to the gate of the transistor Tr via The output voltage of the gain adjustment amplifier AMP (gate input voltage of the transistor Tr) is VT1.

4A to 4C are diagrams showing the relationship between the gate input voltage VT1 of the transistor Tr and the output voltage (compensation voltage) Va (voltage at point A in FIG. 3) of the compensation voltage circuit 3. As apparent from FIGS. 4A to 4C, the compensation voltage Va of the compensation voltage circuit 3 monotonously decreases as the temperature increases regardless of the gate input voltage VT1 in the temperature range of −40 ° C. to 20 ° C. The characteristics to be shown.
It has been clarified by simulation that the temperature characteristic of the compensation voltage Va changes according to the temperature characteristic of the gate input voltage VT1 at a temperature of about 20 ° C. or higher. As shown in FIG. 4 (a), when the gate input voltage VT1 is a voltage that decreases monotonously with an increase in temperature, the compensation voltage Va becomes a temperature range as indicated by γ in FIG. 4 (a). It shows a characteristic that decreases with increasing. Further, when the gate input voltage VT1 is constant with respect to the increase in temperature, the compensation voltage Va exhibits a substantially constant characteristic with respect to the increase in temperature as in the temperature range indicated by γ in FIG. 4B. . Further, when the gate input voltage VT1 is a voltage that increases monotonously with increasing temperature, the compensation voltage Va exhibits a characteristic that increases with increasing temperature as in the temperature range indicated by γ in FIG. 4C. .

FIG. 5A is a diagram illustrating a configuration of the compensation voltage circuit 4 according to the fourth embodiment.
The compensation voltage circuit 4 includes, as the compensation voltage generator 12, an operational amplifier OP, variable resistors R1 and R2, n transistors Tr1 to Trn, a reference voltage V1, and n amplifiers AMP1 to AMPn whose gains can be adjusted.
The output line of the temperature sensor 11 is connected to the inverting input terminal of the operational amplifier OP via the variable resistor R1, and the reference voltage V1 is applied to the non-inverting input terminal, and the inverting input terminal and the output terminal A of the operational amplifier OP are connected. Are connected via a variable resistor R2 (feedback resistor). The output line of the temperature sensor 11 is connected to the input line of the i-th (i = 1 to n) amplifier AMPi, and the output line of this amplifier AMPi is connected to the gate terminal (third terminal) of the i-th transistor Tri. To do. The compensation voltage circuit 4 is configured by connecting the drain terminal (first terminal) of the i-th transistor Tri to the inverting input terminal of the operational amplifier OP and connecting the source terminal (second terminal) to the output of the operational amplifier OP. That is, a configuration in which n transistors Tr1 to Trn are connected in parallel is connected to the inverting input terminal and the output terminal of the operational amplifier OP.

FIG. 5B is a graph showing the temperature characteristics of the output voltage VTi (gate input voltage) of the i-th (i = 1 to n) amplifier AMPi in FIG. FIG. 5C is a diagram showing the temperature characteristics of the output voltage (compensation voltage) Va of the compensation voltage circuit 4. When the temperature is low, all the n transistors Tri (i = 1 to n) are in the OFF state, and only the operational amplifier OP operates. The temperature characteristic of the compensation voltage Va at that time is in the range indicated by α in FIG.
As the temperature rises, the transistors Tri are turned on one after another from the one with the higher gate input voltage Vti, the source current by the gate input voltage Vti flows, and the compensation voltage Va is obtained. Therefore, the compensation voltage Va has a characteristic of being connected in a polygonal line shape. Moreover, it is a feature of the present invention that the vicinity of the connection point between the straight lines representing the relationship between the temperature and the compensation voltage Va exhibits a smooth curve. Thus, by using a plurality of amplifiers AMPi whose gain can be adjusted and a plurality of transistors Tri, the temperature characteristic of the compensation voltage Va can be made smoother. It has the effect of smoothing and suppressing the occurrence of frequency dip.

  FIG. 6 is a diagram illustrating a configuration of the compensation voltage circuit 5 according to the fifth embodiment. The difference from the compensation voltage circuit 3 shown in FIG. 3 is that the anode terminal of the diode D is connected to the output terminal A of the operational amplifier OP, and the reference voltage Vref3 is applied to the cathode of the diode D. When the temperature rises and the output voltage (compensation voltage Va) of the operational amplifier OP becomes lower than the reference voltage Vref3, the diode D becomes forward biased, and the voltage at the point A becomes the clip voltage Vref3. When the temperature further rises, the output voltage of the operational amplifier OP further decreases, but since it is clipped by the clip voltage Vref3, it becomes a constant voltage Vref3 as shown in FIG.

FIG. 7A is a diagram illustrating a configuration of the compensation voltage circuit 6 according to the sixth embodiment. Of the compensation voltage circuit 6 shown in FIG. 7A, a first compensation voltage generator including a gain adjusting amplifier AMP1, variable resistors R1 and R2, an operational amplifier OP1, and a transistor Tr1 (N-channel MOSFET) includes: The circuit configuration is the same as that of the compensation voltage generator 12 shown in FIG. 2, and the operation is also the same. That is, if the output voltage Vs of the temperature sensor 11 has a characteristic that increases linearly with the temperature rise as shown in FIG. 7B, the temperature characteristic of the voltage Va1 at the output terminal A1 of the operational amplifier OP1 is: The characteristics are as shown in FIG.
Of the compensation voltage circuit 6 shown in FIG. 7A, a second compensation voltage generator including a gain adjusting amplifier AMP2, variable resistors R3 and R4, an operational amplifier OP2, and a transistor Tr2 (P-channel MOSFET) includes: The circuit configuration is almost the same as that of the compensation voltage circuit 2 shown in FIG. 2 except that the gain adjustment amplifier AMP2 is an inverting amplifier and the transistor Tr2 is a P-channel MOSFET.
In this case, the characteristic of the compensation voltage Va2 of the second compensation voltage generator is as shown in FIG. Therefore, by inputting the output voltage Va1 of the operational amplifier OP1 and the output voltage Va2 of the operational amplifier OP2 to the adder K, the output voltage of the adder K, that is, the compensation voltage Va3 of the compensation voltage circuit 6 is shown in FIG. e) The characteristic exhibits a negative cubic curve as shown. By using such a compensation voltage Va3 as a compensation voltage of a piezoelectric vibrator exhibiting a cubic curve, it is possible to perform temperature compensation of an oscillation circuit having only one variable capacitance element.

  FIG. 8 is a circuit diagram showing the configuration of the temperature-compensated piezoelectric oscillator, and the compensation voltage circuit 6 is obtained by removing the adder K from the compensation voltage circuit 6 shown in FIG. In this example, the compensation voltages Va1 and Va2 of the operational amplifiers OP1 and OP2 of the compensation voltage circuit 6 are connected to the two variable capacitance elements Cv1 and Cv2 of the piezoelectric oscillator 10, respectively. The piezoelectric oscillator 10 is a known oscillator including an amplifier AI, two capacitors C1 and C2, a piezoelectric vibrator X, and two variable capacitance elements Cv1 and Cv2, as shown in FIG. The output voltage (compensation voltage Va1) of the operational amplifier OP1 of the compensation voltage circuit 6 is connected to one terminal of the variable capacitor Cv1 through the resistor R6, and the other terminal of the variable capacitor Cv1 is grounded. The output (compensation voltage Va2) of the operational amplifier OP2 of the compensation voltage circuit 6 is connected to one terminal of the variable capacitance element Cv2 via the resistor R7, and the other terminal of the variable capacitance element Cv2 is grounded. The temperature compensation of the piezoelectric vibrator X whose frequency-temperature characteristic exhibits a cubic curve at a temperature lower than normal temperature is performed by applying a compensation voltage Va1 shown in FIG. 7C to the variable capacitance element Cv1. As for temperature compensation at a temperature higher than normal temperature, temperature compensation can be performed by applying a voltage Va2 having compensation voltage characteristics shown in FIG. 7D to the variable capacitance element Cv2.

FIG. 9 is a circuit diagram showing the configuration of a temperature compensated piezoelectric oscillator. The compensation voltage circuit 6 is basically the same as the compensation voltage circuit 6 shown in FIG. 8, but the transistor Tr2 is an N-channel MOSFET. The difference is that AMP2 is an inverting amplifier. (The reason will be described later.) This embodiment is an example in which two compensation voltages Va1 and Va2 from the compensation voltage circuit 6 are applied to a piezoelectric oscillator 10 having a low-temperature MOS capacitance element ML and a high-temperature MOS capacitance element MH. is there. As is well known, the piezoelectric oscillator 10 includes, for example, a Colpitts oscillation circuit and a temperature compensation circuit. The Colpitts oscillation circuit includes a piezoelectric vibrator X, a transistor Tr10, a plurality of capacitors, and a plurality of resistors.
In addition, the temperature compensation circuit includes, for example, a high-temperature MOS capacitor element MH connected in parallel to a series circuit of a low-temperature MOS capacitor element ML and a capacitor C14, and one terminal of the capacitor C15 is connected to the gate of the low-temperature MOS capacitor element ML. Connect and ground the other terminal.
Further, the reference voltage Vref8 is applied to the connection point between the low temperature MOS capacitor element ML and the high temperature MOS capacitor element MH. The compensation voltage Va1 of the operational amplifier OP1 of the compensation voltage circuit 6 is connected to the back gate of the low-temperature MOS capacitor element ML via the resistor R14, and the compensation voltage Va2 of the operational amplifier OP2 is connected to the high-temperature MOS capacitor via the resistor R15. A temperature compensated piezoelectric oscillator is configured by connecting to the gate of the element MH.

Here, the reason why the transistor Tr2 is an N-channel MOSFET and the AMP2 is inverted will be described. This is because the compensation voltage Va1 is applied to the back gate side of the low temperature MOS capacitor element ML, whereas the compensation voltage Va2 is applied to the gate side of the high temperature MOS capacitor element MH. That is, the circuit of the compensation voltage Va2 (for high temperature compensation) has such a configuration for the purpose of obtaining voltage characteristics that monotonously increase from a constant voltage (low voltage) state with respect to temperature increase.
As described above, by applying the smooth compensation voltage generated from the compensation voltage circuit 6 of the present invention to the temperature compensation circuit, the frequency compensation accuracy of the piezoelectric vibrator is improved, and the straight lines of the compensation voltage are connected to each other. Since the connecting portion is smoothly formed, the occurrence of frequency dip can be suppressed.

(A) is the configuration of the compensation voltage circuit according to the first embodiment of the present invention, (b) is the temperature characteristic of the output voltage of the temperature sensor, (c) is the temperature characteristic of the compensation voltage, (d) and (e ) Is a graph showing temperature characteristics of compensation voltage. The figure which shows the structure of the compensation voltage circuit which concerns on 2nd Embodiment. The figure which shows the structure of the compensation voltage circuit 3 which concerns on 3rd Embodiment. (A), (b), (c) is the figure which showed the temperature characteristic of the gate input voltage and the output voltage of the compensation voltage circuit 3. FIG. (A) is a figure which shows the structure of the compensation voltage circuit which concerns on 4th Embodiment, (b) is a figure which shows a gate input, (c) is a figure which shows the output voltage characteristic of the compensation voltage circuit 4. FIG. (A) is a figure which shows the structure of the compensation voltage circuit which concerns on 5th Embodiment, (b) is a figure which shows the temperature characteristic of compensation voltage. (A) is a figure which shows the structure of the compensation voltage circuit which concerns on 6th Embodiment, (b) is the temperature characteristic of a temperature sensor, (c) is the output voltage characteristic of operational amplifier OP1, (d) is operational amplifier OP2 (E) is a figure which shows the temperature characteristic of the output voltage of the compensation voltage circuit 6. FIG. The circuit diagram which shows the example which applied the compensation voltage circuit which concerns on 6th Embodiment to the piezoelectric oscillator, and comprised the temperature compensation type | mold piezoelectric oscillator. The circuit diagram which shows the example which applied the compensation voltage circuit which concerns on 6th Embodiment to the piezoelectric oscillator, and comprised the temperature compensation type | mold piezoelectric oscillator. The figure which shows the structure of the temperature compensation crystal oscillator provided with the conventional function generation circuit. The figure which shows the control voltage which a control circuit produces | generates. The figure which shows the structure of the temperature compensation type | mold piezoelectric oscillator provided with the clip voltage generation circuit. The figure which shows the temperature characteristic of compensation voltage.

Explanation of symbols

  1, 2, 3, 4, 5, 6 ... compensation voltage circuit, 10 ... oscillator, 11 ... temperature sensor, 12 ... compensation voltage generator, R, R1, R2, R3, R4, R6, R7, R11, R12, R14, R15, R16 ... resistor, C, C1, C2, C11, C12, C14, C15 ... capacitance, Cv1, Cv2 ... variable capacitance element, Vs ... output voltage of temperature sensor, V1, V3, Vref, Vref2, Vref3, Vref4 ... reference voltage, OP, OP1, OP2 ... operational amplifier, Tr, Tr1, Tr2, Trn ... transistor, AMP, AMP1, AMP2, AMPn ... gain adjusting amplifier, VT1, VT2, VTn ... amplifier output, Va, Va1 , Va2, Va3 ... compensation voltage, K ... adder

Claims (7)

  A temperature sensor;
  A compensation voltage generator having a transistor, an operational amplifier that amplifies the output signal of the temperature sensor, and a gain adjustment amplifier that performs gain adjustment,
  The output signal terminal of the temperature sensor and the first terminal of the transistor and the inverting input terminal of the operational amplifier are connected, and the second terminal of the transistor and the output terminal of the operational amplifier are connected,
  The compensation voltage circuit, wherein the gain adjusting amplifier is connected between the output signal terminal and the third terminal of the transistor, and generates a compensation voltage according to a temperature detection result of the temperature sensor.   The transistors are a plurality of transistors connected in parallel, and a first terminal of each of the plurality of transistors is connected to an inverting input terminal of the operational amplifier, and a second terminal of each of the plurality of transistors is the arithmetic operation 2. The compensation voltage circuit according to claim 1, wherein the compensation voltage circuit is connected to an output terminal of the amplifier.   A first terminal of the transistor is a drain terminal of the transistor, a second terminal of the transistor is a source terminal of the transistor, and a third terminal of the transistor is a gate terminal of the transistor. The compensation voltage circuit according to claim 1.   4. The compensation voltage generator according to claim 1, further comprising a diode, supplying an output signal of the operational amplifier to a cathode terminal of the diode and applying a reference voltage to an anode terminal of the diode. The compensation voltage circuit according to any one of the above.   The compensation voltage circuit according to claim 1, wherein the transistor is an N-channel MOSFET or a P-channel MOSFET.   2. The compensation voltage generation unit is provided in two, the transistor of one of the compensation voltage generation units is an N-channel MOSFET, and the transistor of the other compensation voltage generation unit is a P-channel MOSFET. The compensation voltage circuit as described in any one of thru | or 4.   A temperature-compensated piezoelectric oscillator comprising the compensation voltage circuit according to claim 1.

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