JP2005167510A - Temperature compensation piezoelectric oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a temperature compensation piezoelectric oscillator by avoiding a temperature compensation voltage from being a voltage at a minimum capacitance (Cmin) so as to suppress variations in a load capacitance at a high temperature in order to avoid an unstable region caused around the minimum capacitance in C-V characteristics of a MOS varactor. <P>SOLUTION: The temperature compensation piezoelectric oscillator 100 is configured to include an oscillation circuit 12 and a frequency temperature compensation circuit 1, and the frequency temperature compensation circuit 1 is configured to include: a temperature detection section 3 whose parameter changes with ambient temperature; a temperature compensation voltage generating circuit (temperature compensation voltage generating section) 2 for generating voltages on the basis of the changed parameter of the temperature detection section 3; MOS capacitive elements MH 10, ML 11 whose capacitance is changed with a voltage difference between temperature compensation voltages (VH, VL) generated from the temperature compensation voltage generating circuit 2 and a reference voltage (Vref): clip voltage generating circuits (clip voltage generating means) 4, 5 for clipping the temperature compensation voltages to be a prescribed voltage; DC block capacitors 7, 9; and fixed resistors 6, 8. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a piezoelectric oscillator using a piezoelectric vibrator such as a crystal vibrator, and in particular, in a piezoelectric oscillator that performs temperature compensation using a MOS capacitive element, avoids an unstable region in the CV characteristics of the MOS capacitive element. The present invention relates to a circuit configuration.

In recent years, a piezoelectric oscillator in which an oscillation circuit, a temperature compensation circuit, and the like are added to a piezoelectric vibrator such as a crystal vibrator has been strictly demanded not only for frequency stability but also for miniaturization and cost reduction. The output frequency of a piezoelectric oscillator changes due to various factors. Even in a crystal oscillator with relatively high frequency stability, there are frequency fluctuations due to changes in conditions such as ambient temperature, power supply voltage, and output load. Various means have been proposed. For example, with regard to temperature changes, a temperature compensation circuit is added to the crystal oscillator, and the load capacity of the oscillation loop of this temperature compensated crystal oscillator (hereinafter referred to as TCXO) is changed to cancel the temperature-frequency characteristic variation inherent in the crystal oscillator. As described above, there is one that controls the load capacity with respect to a temperature change, and there are roughly three compensation methods: a direct temperature compensation method, an indirect temperature compensation method, and a digital compensation method.
In particular, as an indirect temperature compensation method, there is one in which a temperature compensation circuit is configured using a MOS varactor, and there are several structures in this MOS varactor. For example, an accumulation type, a P-channel transistor type, or the like can be given. A method using a P-channel transistor type MOS varactor has been filed as Japanese Patent Application No. 2003-287153 from the same applicant.
FIG. 6 is a diagram showing an example of a temperature compensation circuit using a conventional MOS varactor. This uses a low-temperature compensation MOS type varactor ML43 and a high-temperature compensation MOS type varactor MH46. The MOS type varactor has resistances 44, 41, 45 at one end and a control voltage VL, VH at the other end. Applied. With such a configuration, a third-order capacitance change with respect to temperature is obtained in order to compensate for the third-order temperature characteristics of the crystal resonator. In addition, the indirect temperature compensation method using such a MOS varactor is characterized in that the compensation voltages VL and VH can be linearly changed.
Japanese Patent Application No. 2003-287153

However, in the case of the accumulation type, the relationship between the potential difference applied to the MOS type varactor and the capacitance (hereinafter referred to as CV characteristic) 40 as shown in FIG. There is a problem that it takes time to stabilize after application. Since the vicinity of Cmin is used near the room temperature of the high-temperature compensation circuit in the indirect temperature compensation method, the instability of Cmin affects the frequency stability of the oscillator at room temperature. That is, in the vicinity of Cmin, the stabilization time at the time of voltage application is slow, which affects the frequency startup time as an oscillator, and may not satisfy the current specifications required for high-speed startup.
Patent Document 1 discloses a CV characteristic in which a bias is applied between a P-type extraction electrode formed in a source and drain region of a P-channel transistor and an N-type extraction electrode formed in an N-Well region. This avoids an unstable region near the minimum capacitance value (Cmin), necessitating the development of a new semiconductor process, and has the problem of requiring development costs and a great deal of development time.
In view of such a problem, the present invention avoids a potential difference when the temperature compensation voltage is the minimum capacitance value in order to avoid an unstable region near the minimum capacitance value (Cmin) in the CV characteristic of the MOS varactor. An object of the present invention is to provide a temperature-compensated piezoelectric oscillator that suppresses load capacity fluctuation at high temperatures.
Another object is to solve the problem of the conventional accumulation-type MOS varactor with an external circuit configuration, thereby eliminating the need for development of a new semiconductor process and greatly reducing development costs.

In order to solve the above problems, the present invention provides a piezoelectric vibrator including a piezoelectric element excited at a predetermined frequency, an oscillation amplifier that excites the piezoelectric element by passing a current, and a temperature change. A frequency oscillator circuit comprising a frequency temperature compensation circuit that compensates for a change in oscillation frequency due to a temperature detection unit, wherein the frequency temperature compensation circuit includes a temperature detection unit whose parameter changes according to an ambient temperature, and a parameter that is changed by the temperature detection unit A temperature compensation voltage generator that generates a voltage based on the plurality of MOS capacitance elements whose capacitance changes based on a potential difference between the temperature compensation voltage generated by the temperature compensation voltage generator and a reference voltage; and And a plurality of clip voltage generating means for clipping the temperature compensation voltage to a predetermined voltage.
Basically, the temperature compensation circuit, if the temperature detection unit configured to detect the ambient temperature and, for example, the thermistor is constituted by a thermistor, takes out as a voltage change by resistance voltage division and generates a voltage based on the voltage change. The temperature compensation voltage generator is composed of a MOS capacitance element having a third-order capacitance characteristic due to a potential difference between the voltage and a reference voltage. However, the MOS capacitance element has a characteristic that the capacitance value on the low potential side becomes unstable, and this instability is a factor of frequency fluctuation. Therefore, the present invention further includes clip voltage generation means for clipping the output of the temperature compensation voltage generator that varies linearly with temperature so that the capacitance value of the MOS capacitor does not become unstable. As a result, the potential does not fall below a certain potential.
According to this invention, the temperature compensation circuit is further provided with the clipping voltage generation means, and the output of the temperature compensation voltage generator that changes linearly with the temperature is clipped near the normal temperature, so that the capacitance value of the MOS capacitor element is unstable. Thus, the frequency stability on the high temperature side can be further increased.
In this specification, the piezoelectric element refers to an element in which excitation electrodes and lead terminals are formed on the main surface of the piezoelectric substrate, and the piezoelectric vibrator refers to the piezoelectric element itself or the piezoelectric element hermetically sealed. An electronic component is designated.

According to a second aspect of the present invention, the temperature compensation voltage generator compensates a temperature characteristic on a low temperature side centering on a room temperature of the temperature characteristic of the piezoelectric element, and a reference control voltage generator that generates a reference voltage having a predetermined potential. A low temperature control voltage generator that generates a voltage, and a high temperature control voltage generator that generates a voltage that compensates for temperature characteristics on the high temperature side, and the clip voltage generator includes the low temperature control voltage generator and the high temperature control voltage. Each output of the generation unit is clipped so as not to be equal to or less than a potential difference in a low capacitance value region in the CV characteristic of the MOS capacitance element.
Basically, if the temperature compensation circuit is composed of a thermistor and a temperature detector that detects the ambient temperature, for example, a temperature change is extracted as a voltage change by resistance voltage division, and a temperature lower than normal temperature based on the voltage change. There are a low temperature control voltage generator that controls the voltage to rise in a range, and a high temperature control voltage generator that controls the voltage to rise in a temperature range higher than room temperature. In the present invention, the clip voltage generating means clips the characteristic that these outputs change linearly with a temperature change so that it does not become a predetermined voltage or less near room temperature. It is possible to avoid an unstable region in a low capacitance value region in the CV characteristics of the MOS capacitor element by setting the voltage to a constant voltage on the low temperature side.
According to this invention, the clip voltage generating means clips the outputs of the low temperature control voltage generator and the high temperature control voltage generator so as not to be less than the potential difference of the low capacitance value region in the CV characteristic of the MOS capacitor. Therefore, instability of the capacitance value with respect to potential change in the low capacitance value region of the MOS capacitance element can be avoided.
According to a third aspect of the present invention, the clip voltage generating means has a predetermined potential difference from the reference voltage over the high temperature side and the low temperature side around the normal temperature around each output of the low temperature control voltage generation unit and the high temperature control voltage generation unit. It is controlled to become a constant voltage of.
For example, when there is no clip voltage generation means, the voltage of the low temperature control voltage generator is a voltage that drops linearly from the low temperature side, and the voltage of the high temperature control voltage generator is a voltage that increases linearly from the high temperature side. Yes, cross at almost normal temperature. If this voltage is applied to the MOS capacitor element, the capacitance value of the MOS capacitor element becomes unstable, particularly on the low temperature side where the voltage of the high temperature control voltage generator is lowered, and as a result, the frequency on the high temperature side becomes unstable. .
According to this invention, the clip voltage generating means is configured such that each of the outputs of the low temperature control voltage generation unit and the high temperature control voltage generation unit has a predetermined constant potential difference from the reference voltage over the high temperature side and the low temperature side centered around the normal temperature. Since the voltage is controlled to be a voltage, a potential at which the capacitance value of the MOS capacitance element becomes unstable can be avoided, and as a result, the frequency on the high temperature side can be further stabilized.

According to a fourth aspect of the present invention, the clip voltage generation means includes a clip voltage generation source that generates a clip voltage and a diode, and the voltage value of the clip voltage generation source can be arbitrarily set.
As an example of the clip voltage generation means, a clip voltage generation source and an anode of a diode are connected, and the cathode side is connected to each output of a low temperature control voltage generation unit and a high temperature control voltage generation unit. With this circuit configuration, when the control voltage is higher than the clip voltage, the control voltage is output as it is as a reverse bias, but when the control voltage is lower than the clip voltage, it becomes a forward bias and the clip voltage is output as it is. Therefore, if the clip voltage can be arbitrarily set, the clip voltage can be set with various voltages.
According to this invention, since the clip voltage generation means can arbitrarily set the voltage value of the clip voltage generation source, the clip voltage can be set with various voltages.
According to a fifth aspect of the present invention, the plurality of MOS capacitance elements include a low temperature portion compensation MOS capacitance element that compensates for a low temperature temperature characteristic centered on a normal temperature characteristic of the piezoelectric element, and a high temperature temperature compensation for the high temperature temperature characteristic. The low-temperature portion compensation MOS capacitance element is controlled by the temperature compensation voltage generation means so that the load capacitance of the piezoelectric oscillator is reduced near the room temperature and below. In addition, the high temperature compensation MOS capacitor is controlled by the temperature compensation voltage generating means so that the load capacity of the piezoelectric oscillator is increased near the room temperature and above.
The characteristic of the MOS capacitor element has a characteristic that the capacitance value increases nonlinearly as the applied voltage increases. Therefore, the output voltage rises when the temperature falls on the low temperature side with respect to the normal temperature, and the output voltage rises when the temperature rises on the high temperature side, and this voltage is applied to the MOS capacitor element. For example, if the temperature decreases with the normal temperature as a reference, the capacity decreases and the frequency is increased. Conversely, if the temperature increases with the normal temperature as a reference, the capacity increases and the frequency is decreased.
According to this invention, by incorporating the MOS capacitance element into the frequency temperature compensation circuit, the temperature change is applied as a voltage change to the variable capacitance element, so that the temperature characteristics of the crystal resonator can be compensated more finely.

According to a sixth aspect of the present invention, a parallel circuit in which the low-temperature portion compensation MOS capacitor element and the high-temperature portion compensation MOS capacitor element are connected in parallel so as to have different polarities is inserted into an oscillation loop of the oscillator, An output terminal of the reference control voltage generator is connected to a connection point between the MOS capacitor element and the high-temperature part compensation MOS capacitor element via a resistor, and the low-temperature control voltage generator is generated at the other end of the low-temperature part compensation MOS capacitor element. And connecting the output terminal of the high-temperature control voltage generator and the clip voltage generator to the other end of the high-temperature compensation MOS capacitor element. It is characterized by connecting via.
The basics of temperature compensation are to insert a MOS capacitance element in the oscillation loop so that the capacitance of the MOS capacitance element changes with temperature, and the capacitance change works as part of the load capacitance of the oscillation loop. It is. The MOS capacitance element of the present invention is prepared with two devices that compensate for the low temperature side and one that compensates for the high temperature side, and the polarities are reversed and connected in parallel, and each terminal is connected via a resistor. A clip voltage generating means is connected.
According to this invention, two MOS capacitor elements that compensate for the low temperature side and two that compensate for the high temperature side are prepared and connected in parallel with their polarities reversed, and resistors are connected to the respective terminals. Since the clip voltage generating means is connected to the low voltage side, the control voltage on the low temperature side and the high temperature side can be configured in contrast to the normal temperature, and the low and high temperature voltages can be kept constant around the normal temperature. can do.
According to a seventh aspect of the present invention, a capacitor element is connected in series to one of the MOS capacitor elements in a parallel circuit in which the low-temperature portion compensation MOS capacitor element and the high-temperature portion compensation MOS capacitor element are connected in parallel with different polarities. The output voltage of the low temperature control voltage generator and the output voltage of the high temperature control voltage generator are separated in a DC manner.
By connecting a fixed capacitor element in series to either the low-temperature side or the high-temperature side MOS capacitor element, it is possible to serve to cut the high-temperature side voltage and the low-temperature side voltage in a DC manner.
According to this invention, since the low-temperature side voltage and the high-temperature side voltage can be cut and applied individually with respect to the reference voltage, an accurate control voltage can be applied to the temperature change.

As described above, according to the first aspect of the present invention, the temperature compensation circuit is further provided with the clipping voltage generating means, and the output of the temperature compensating voltage generating section that changes linearly with temperature is clipped in the vicinity of the normal temperature. By avoiding the region where the capacitance value of the element becomes unstable, the stability of the frequency on the high temperature side can be further increased.
According to a second aspect of the present invention, the clip voltage generating means clips the outputs of the low temperature control voltage generator and the high temperature control voltage generator so as not to be less than the potential difference of the low capacitance value region in the CV characteristic of the MOS capacitor. Therefore, instability of the capacitance value with respect to potential change in the low capacitance value region of the MOS capacitance element can be avoided.
According to a third aspect of the present invention, the clip voltage generating means is configured such that each of the outputs of the low temperature control voltage generation unit and the high temperature control voltage generation unit has a predetermined constant potential difference from the reference voltage over the high temperature side and the low temperature side centered around the normal temperature. Since the voltage is controlled to be a voltage, a potential at which the capacitance value of the MOS capacitance element becomes unstable can be avoided, and as a result, the frequency on the high temperature side can be further stabilized.
According to the fourth aspect of the present invention, since the clip voltage generation means can arbitrarily set the voltage value of the clip voltage generation source, the clip voltage can be set with various voltages.
According to the fifth aspect of the present invention, since the temperature change is applied to the variable capacitance element as a voltage change by incorporating the MOS capacitance element in the frequency temperature compensation circuit, the temperature characteristics of the crystal resonator can be compensated more finely.
According to the sixth aspect of the present invention, two MOS capacitor elements, one for compensating the low temperature side and the other for compensating the high temperature side, are prepared and connected in parallel with their polarities reversed, and resistors are connected to the respective terminals. Since the clip voltage generating means is connected to the low voltage side, the control voltage on the low temperature side and the high temperature side can be configured in contrast to the normal temperature, and the low and high temperature voltages can be kept constant around the normal temperature. can do.
According to the seventh aspect of the present invention, since the low-temperature side voltage and the high-temperature side voltage can be individually applied by cutting them with respect to the reference voltage, an accurate control voltage can be applied to the temperature change.

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the components, types, combinations, shapes, relative arrangements, and the like described in this embodiment are merely illustrative examples and not intended to limit the scope of the present invention only unless otherwise specified. .
First, before describing the embodiment of the present invention, the most principal technical principle of the present invention will be described with reference to FIG. 4 and FIG. FIG. 4A is a diagram illustrating the CV characteristics of the MOS varactor. From this figure, the principle of temperature compensation is schematically explained. Using the rising region (B region) and falling region (A region) of the CV characteristic 50 of the MOS varactor, low temperature compensation and high temperature compensation can be performed. It is the structure to perform. FIG. 4B is a diagram showing the relationship between the load capacity and temperature (compensation capacity curve) when the MOS varactor having the characteristics shown in FIG. 4A is used. The low temperature region C is generated by a MOS varactor ML for low temperature portion compensation described later, and the high temperature region D is generated by a MOS varactor MH for high temperature portion compensation described later. As a result, the frequency of the crystal resonator is temperature compensated. Therefore, it is possible to obtain the characteristic of the capacity curve 51 for the purpose. That is, MOS type varactors are required for low temperature and high temperature, respectively.
FIG. 5A shows the relationship between the high temperature compensation voltage and the temperature. That is, as shown in FIG. 5 (b), the left side region (use region) in the rising curve 31 of the CV characteristic of the MOS varactor is used for the high temperature compensation. In the temperature region, the VH 33 is controlled to be a constant voltage, and when reaching a high temperature region that requires temperature compensation, the VH 33 is controlled so that the voltage rises as the temperature rises, whereby Vref 32 and VH 33 are controlled. Are equal (potential difference = 0), the point P is set to a high temperature portion of the compensation temperature. The conventional compensation voltage 34 linearly changes even in the temperature region outside the compensation range, as shown by the broken line in FIG. In this case, since the Cmin part (29 area in FIG. 5B) of the CV characteristic is used in a wide area, the problem described above has occurred. Therefore, in order to solve this problem, it is useful to use only the region 30 in FIG. 5B. For this purpose, the voltage limit function (voltage) is used so that the voltage is constant up to the point Q in FIG. Clip function).

FIG. 1 is a block diagram showing a partial configuration of a temperature compensated piezoelectric oscillator according to the present invention. This temperature-compensated piezoelectric oscillator 100 is roughly composed of a piezoelectric vibrator (quartz crystal vibrator) X including a piezoelectric element excited at a predetermined frequency, and an oscillation amplifier that excites the piezoelectric element by passing a current. The oscillation circuit 12 and a frequency temperature compensation circuit 1 that compensates for a change in oscillation frequency due to a temperature change are provided. The oscillation circuit 12 is a Colpitts oscillation circuit in the figure, but may be another oscillation circuit.
The frequency temperature compensation circuit 1 includes a temperature detection unit 3 whose parameters change according to the ambient temperature, and a temperature compensation voltage generation circuit (temperature compensation voltage generation unit) that generates a voltage based on the parameters changed by the temperature detection unit 3. ) 2, MOS capacitance elements MH 10 and ML 11 whose capacitance changes based on the potential difference between the temperature compensation voltages (VH and VL) generated by the temperature compensation voltage generation circuit 2 and the reference voltage (Vref), and temperature compensation Clip voltage generating circuits (clip voltage generating means) 4 and 5 for clipping the operating voltage to a predetermined voltage, DC blocking capacitors 7 and 9, and fixed resistors 6 and 8.
A connection point P between the counter electrode of the ML (low-temperature portion compensation MOS capacitor) 11 and the capacitor 7 is connected to a low-temperature control voltage terminal (hereinafter referred to as VL) via a resistor 6, and further a clip voltage generation circuit. 4 is connected. The other end of the capacitor 7 is grounded via a capacitor 9, its connection midpoint Q is connected to a counter electrode of an MH (high temperature part compensation MOS capacitor element) 10, and a high temperature control voltage terminal ( (Hereinafter referred to as VH) and a clip voltage generation circuit 5 is further connected. In addition, a connection midpoint R where the counter electrodes of ML and MH are connected to each other is connected to a piezoelectric vibrator (quartz crystal vibrator) X and also connected to Vref via a resistor 13. In the clip voltage generation circuit 4 of the present embodiment, the diode D and the clip power supply Vcl1 are connected in series, and the cathode of the diode D is connected to VL. In the clip voltage generation circuit 5, the diode D and the clip power supply Vcl2 are connected in series, and the cathode of the diode D is connected to VH. Further, the voltage of the clip power supply Vcl1 and the clip power supply Vcl2 can be adjusted.

  FIG. 2 is a graph showing temperature characteristics of the compensation voltage according to the present invention. The vertical axis represents the compensation voltage, and the horizontal axis represents the ambient temperature. This will be described with reference to FIG. Vref generated from the temperature compensation voltage generation circuit 2 is, for example, a positive constant voltage 21 and is supplied to the connection point R via the resistor 13. Since the connection point R is connected to different polarities of ML and MH, the connection point R is reverse-biased with respect to ML and forward-biased with respect to MH. In this state, the operation of the voltage VL20 will be described assuming that the temperature continuously changes from −40 ° C. to + 90 ° C. VL20 is at the intersection R ′ with Vref at −40 ° C., and the capacity of ML11 at that time is a predetermined capacity when the voltage between terminals of ML11 is 0 V (FIG. 4B, when the potential difference is 0V). Capacity). When the temperature rises, VL20 decreases linearly, and accordingly, the potential difference of ML11 increases and the capacity increases. At around + 25 ° C., since VL becomes lower than the clip voltage Vcl1 of the clip voltage generation circuit 4, the diode D of the clip voltage generation circuit 4 becomes forward biased, and the voltage at the connection midpoint P ′ becomes the voltage of the clip voltage Vcl1. . Thereafter, when the temperature rises, VL20 further decreases, but the voltage at the connection midpoint P is clipped by the clip voltage Vcl1 and becomes constant.

Next, the operation of the voltage VH22 will be described on the assumption that the temperature has continuously changed from + 90 ° C. to −40 ° C. VH22 is at the intersection S with Vref at + 90 ° C., and the capacity of MH10 at that time is a predetermined capacity when the voltage between the terminals of MH10 is 0 V (FIG. 4B, the capacity of potential difference 0V). When the temperature decreases, VH22 decreases linearly, and accordingly, the potential difference of MH10 increases and the capacity decreases. At around + 25 ° C., VH22 becomes lower than the clip voltage Vcl2 of the clip voltage generation circuit 5, so that the diode D of the clip voltage generation circuit 5 becomes forward biased and the voltage at the connection midpoint Q becomes the voltage of the clip voltage Vcl2. After that, when the temperature decreases, VH22 further decreases, but the voltage at the midpoint of connection Q is clipped by the clip voltage Vcl2 and becomes constant.
For low temperature compensation, since the Cmax side in the CV characteristic of the MOS varactor is used (see FIG. 4A), there is no problem due to the unstable region (Cmin) of the CV characteristic. By clipping the VL as in the form, the voltage near the normal temperature can be made unchanged. That is, in the conventional case, in the saturation region of the C-V characteristics of the MOS varactor, the capacitance does not change (= the frequency is stable) even if VH and VL change. (Characteristic that changes voltage even when out of range). However, in reality, depending on the characteristic variation between element solids, there was a case where it was not a complete saturation region such as a large capacitance change (having sensitivity) even near room temperature, but in the case of the temperature compensated piezoelectric oscillator according to the present invention, the temperature Unnecessary fluctuations in the load capacity due to variations in characteristics between the solids of the MOS type varactor can be prevented with respect to outside the compensation range, so that the frequency stability is excellent particularly in the vicinity of room temperature. Furthermore, when temperature compensation is performed as TCXO, conventionally, with respect to the VH and VL voltages, voltage offset adjustment as shown in FIG. 3A and gain adjustment as shown in FIG. The voltage in the (B region) changes. At this time, if the capacitance value does not change, there is no problem, but VL25, 29, VH26, 30 will change. Therefore, the room temperature frequency used as a reference is shifted due to temperature compensation, and a state in which temperature compensation is very difficult has occurred. Therefore, in the present embodiment, by providing the clip voltage generation circuits 4 and 5, the voltage near room temperature is clipped to a constant value, so that the capacitance (frequency) is stable, so the reference frequency is changed unnecessarily. The above-described voltage offset and gain adjustment can be performed without any problem.

The block diagram which shows the partial structure of the temperature compensation type | mold piezoelectric oscillator of this invention. It is a figure showing the temperature characteristic of the compensation voltage of this invention. The figure showing a mode that the voltage near normal temperature changes in order to perform voltage offset adjustment and Gain adjustment regarding VH and VL voltage when temperature compensation is performed as TCXO. The figure explaining the main technical principle of this invention. The figure explaining the main technical principle of this invention. The figure which shows an example of the temperature compensation circuit using the conventional MOS type | mold varactor. The figure showing the relationship between the electric potential difference applied to MOS type varactor, and a capacity | capacitance.

Explanation of symbols

  1 frequency temperature compensation circuit, 2 temperature compensation voltage generation circuit, 3 temperature detection unit, 4, 5 clip voltage generation circuit, 6, 8, 13 resistance, 7, 9 DC blocking capacitor, 10, 11 MOS capacitance element, X Crystal oscillator

Claims (7)

A piezoelectric vibrator having a piezoelectric element excited at a predetermined frequency, an oscillation amplifier that excites the piezoelectric element by passing a current, and a frequency temperature compensation circuit that compensates for a change in oscillation frequency due to a temperature change. A piezoelectric oscillator,
The frequency temperature compensation circuit includes a temperature detection unit whose parameter changes according to the ambient temperature, a temperature compensation voltage generation unit that generates a voltage based on the parameter changed by the temperature detection unit, and the temperature compensation voltage generation unit. A plurality of MOS capacitors whose capacitance changes based on a potential difference between the generated temperature compensation voltage and a reference voltage, and a plurality of clip voltage generation means for clipping the temperature compensation voltage to a predetermined voltage. A temperature compensated piezoelectric oscillator. The temperature compensation voltage generator includes a reference control voltage generator that generates a reference voltage having a predetermined potential, and a low temperature that generates a voltage that compensates for the temperature characteristics on the low temperature side centered on the temperature characteristics of the piezoelectric element. A control voltage generator, and a high temperature control voltage generator that generates a voltage that compensates for temperature characteristics on the high temperature side,
The clip voltage generation means clips the outputs of the low-temperature control voltage generation unit and the high-temperature control voltage generation unit so as not to be equal to or lower than the potential difference in the low capacitance value region in the CV characteristic of the MOS capacitance element. The temperature compensated piezoelectric oscillator according to claim 1.   The clip voltage generation means has a predetermined constant voltage difference between the output of the low temperature control voltage generation unit and the high temperature control voltage generation unit with respect to the reference voltage over the high temperature side and the low temperature side around the normal temperature. The temperature compensated piezoelectric oscillator according to claim 1, wherein the temperature compensated piezoelectric oscillator is controlled as follows.   The temperature according to claim 2, wherein the clip voltage generation means includes a clip voltage generation source for generating a clip voltage and a diode, and the voltage value of the clip voltage generation source can be arbitrarily set. Compensated piezoelectric oscillator.   The plurality of MOS capacitance elements include a low temperature portion compensation MOS capacitance element that compensates for a low temperature temperature characteristic centered on a normal temperature of the piezoelectric element, and a high temperature portion compensation MOS capacitor that compensates for a high temperature temperature characteristic. The low-temperature portion compensation MOS capacitance element is controlled by the temperature compensation voltage generating means so that the load capacitance of the piezoelectric oscillator is reduced near and below the normal temperature, and the high-temperature portion 2. The temperature according to claim 1, wherein the compensation MOS capacitance element is controlled by the temperature compensation voltage generating means so that a load capacitance of the piezoelectric oscillator is increased near the room temperature and above. Compensated piezoelectric oscillator.   A parallel circuit in which the low-temperature portion compensation MOS capacitor element and the high-temperature portion compensation MOS capacitor element are connected in parallel with different polarities is inserted into an oscillation loop of the oscillator, and the low-temperature portion compensation MOS capacitor element and the high-temperature portion compensation MOS capacitor element An output terminal of the reference control voltage generation unit is connected to a connection point with the MOS compensation element for part compensation through a resistor, and an output terminal of the low temperature control voltage generation unit is connected to the other end of the MOS capacitor element for low temperature part compensation. The clip voltage generating means is connected via a resistor, and the output terminal of the high temperature control voltage generating portion and the clip voltage generating means are connected via a resistor to the other end of the high temperature portion compensating MOS capacitance element. The temperature compensated piezoelectric oscillator according to claim 1 or 2.   A capacitor element is connected in series to one of the MOS capacitor elements of a parallel circuit in which the low-temperature part compensation MOS capacitor element and the high-temperature part compensation MOS capacitor element are connected in parallel with different polarities, and the low-temperature control voltage 7. The temperature compensated piezoelectric oscillator according to claim 6, wherein the output voltage of the generator and the output voltage of the high temperature control voltage generator are separated in a DC manner.

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