JP4424001B2 - Temperature compensated piezoelectric oscillator - Google Patents

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, piezoelectric oscillators in which an oscillation circuit, a temperature compensation circuit, and the like are added to a piezoelectric vibrator such as a crystal vibrator have 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 as means. For example, with respect 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 by using a MOS capacitance element, and this MOS capacitance element has several structures. For example, an accumulation type, a P-channel transistor type, or the like can be given. As a solution to this problem, the same applicant has proposed a technique described in Japanese Patent Application No. 2003-287153 regarding a method using a P-channel transistor type MOS capacitor.
FIG. 8 is a diagram showing an example of a temperature compensation circuit using a conventional MOS capacitance element. This is achieved by using a low-temperature compensation MOS capacitor element ML43 and a high-temperature compensation MOS capacitor element MH46. At both ends of the MOS capacitor element, a reference voltage Vref is applied to one end, and control voltages VL and VH are provided with resistors 44, 41, and 45, respectively. 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. The indirect temperature compensation method 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 capacitance element and the capacitance (hereinafter referred to as CV characteristics) 40 as shown in FIG. There is a problem that it takes time to stabilize after application. As a method of solving this problem, there is a method of using a clip voltage generation circuit in order to avoid an unstable region near the capacitance minimum value (Cmin) in the CV characteristic of the MOS capacitance element. In this case, as shown in FIG. 10, it is ideal that the voltages 55 and 58 subjected to clipping control of VH and VL become constant at a voltage that is decreased by the forward voltage of the diode from the clipping voltage. Since the forward voltage has a temperature characteristic of about −2 mV / ° C., the voltages 56 and 57 after clipping have a temperature characteristic of about 2 mV / ° C. As a result, the vicinity of Cmin is used near the normal temperature of the high-temperature compensation circuit in the indirect temperature compensation method, so the instability of Cmin affects the frequency stability of the oscillator at normal 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 an electric 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 capacitance element. In order to compensate for the temperature characteristics of the circuit, a temperature compensated piezoelectric oscillator that simultaneously suppresses fluctuations due to load capacity fluctuations at high temperatures and circuit temperature characteristics by correcting the temperature characteristics of the forward voltage of the diode. The purpose is to provide.
Another object is to solve the problem of the conventional accumulation-type MOS capacitor by an external circuit configuration, thereby eliminating the need for development of a new semiconductor process and greatly reducing development costs.

In order to solve such a problem, the present invention provides a piezoelectric vibrator excited at a predetermined frequency, an oscillation circuit, and a frequency temperature compensation circuit that compensates for a change in oscillation frequency due to a temperature change. The frequency temperature compensation circuit includes: a temperature detection unit whose parameter changes according to an ambient temperature; a temperature compensation voltage generation unit which generates a voltage based on the parameter changed by the temperature detection unit; A MOS capacitance element whose capacitance changes based on the potential difference between the temperature compensation voltage generated by the temperature compensation voltage generator and the reference voltage, and the temperature compensation voltage within the desired temperature range is C− of the MOS capacitance element. and a clip voltage generating means to clip so as not fall below a potential difference of the low capacitance value region in V characteristics, the clipping voltage generating means includes a differential amplifier, chestnut And a first diode provided between the output terminal of the differential amplifier and the output terminal of the frequency temperature compensation circuit, and the differential amplifier constitutes the differential amplifier. Among the plurality of transistors, the second diode is provided so as to be forward-connected to the emitter of the transistor on the inverting input end side, the output terminal of the differential amplifier and the inverting input terminal are connected, and the differential The clip voltage generation source is connected to the non-inverting input terminal of the amplifier .
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 the invention, the temperature compensation circuit is further provided with the clipping voltage generation means, and the output of the temperature compensation voltage generation unit that changes linearly with the temperature is clipped near the normal temperature, so that the capacitance value of the MOS capacitance 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.

To clip the voltage it can be configured by a diode and a reference voltage. However, the diode generally has a characteristic that the forward voltage changes with temperature. Therefore, strictly speaking, the clip voltage changes with temperature only with the diode and the reference voltage, and as a result, the frequency characteristics fluctuate. Therefore, in the present invention, in order to cancel the temperature characteristic due to the diode, the amplifier has a characteristic opposite to the temperature characteristic to cancel it. One method is to use a voltage follower configuration with an amplifier with a diode built in as an input, generate a voltage that combines the reference voltage and the temperature characteristics of the built-in diode, and use that voltage as the clip voltage.
According to this invention, since the output terminal of the amplifier and the negative input terminal are connected to form a voltage follower configuration, and the clip voltage generation source is connected to the positive side of the amplifier, the voltage that cancels the temperature characteristic of the diode is the clip voltage. Therefore, it is possible to generate a clip voltage that compensates for the temperature characteristics of the diode.

According to a second aspect of the present invention, the temperature compensation voltage generator includes a reference control voltage generator that generates a reference voltage having a predetermined potential, and a voltage that compensates for temperature characteristics of the piezoelectric vibrator on a low temperature side centered on a normal temperature. And a high-temperature control voltage generator that generates a voltage that compensates for temperature characteristics of the piezoelectric vibrator on the high-temperature side centered at room temperature , and the MOS capacitor element. Comprises a low temperature part compensating MOS capacitor element to which the output voltage of the low temperature control voltage generator is supplied, and a high temperature part compensation MOS capacitor element to which the output voltage of the high temperature control voltage generator is supplied. , and the the clip voltage generating means, the output voltage and the output voltage of the high-temperature control voltage generation section of the cold control voltage generating unit, a low capacitance region in C-V characteristic of the high-temperature portion compensation MOS capacitor element Potential difference And characterized in that the clip so as not to be under.
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 temperature compensation voltage generator includes a reference control voltage generator that generates a reference voltage having a predetermined potential, and a voltage that compensates for temperature characteristics of the piezoelectric vibrator on the low temperature side centered on room temperature. And a high-temperature control voltage generator that generates a voltage that compensates for temperature characteristics of the piezoelectric vibrator on the high-temperature side centered at room temperature, and the MOS capacitor element. Comprises a low temperature part compensating MOS capacitor element to which the output voltage of the low temperature control voltage generator is supplied, and a high temperature part compensation MOS capacitor element to which the output voltage of the high temperature control voltage generator is supplied. The clip voltage generation means includes a first clip voltage generation means for clipping the output voltage of the low temperature control voltage generation section, and a second clip voltage generation means for clipping the output voltage of the high temperature control voltage generation section. And the second clip voltage generating means outputs the output voltage of the high temperature control voltage generating section in a low capacitance value region in the CV characteristic of the high temperature section compensating MOS capacitance element. It is characterized by clipping so as not to be less than the potential difference .
If the clip voltage is the same on the low temperature side and the high temperature side, the clip voltage may be generated and supplied by one amplifier. However, if the clip voltage is different on the low temperature side and the high temperature side, the two reference voltages and 2 It is necessary to prepare one amplifier and supply a clip voltage to each output individually.
According to this invention, since the clip voltage generating means includes a plurality of amplifiers and clip voltage generation sources, different clip voltages can be individually supplied to the low temperature side and the high temperature side.
According to a fourth aspect of the present invention, the clip voltage generation means can arbitrarily set a voltage value of the clip voltage generation source.
As an example of clip voltage generation means, a clip voltage generation source is connected to a voltage follower type amplifier, its output terminal is connected to the anode of a diode, and its cathode side is connected to a low temperature control voltage generator and a high temperature control voltage generator. Connect to each output. 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 the first aspect of the present invention, the temperature compensation circuit is further provided with the clipping voltage generation means, and the output of the temperature compensation voltage generation unit that changes linearly with the temperature is clipped near the normal temperature. Thus, it is possible to further improve the frequency stability on the high temperature side.
In addition, since the output terminal and the negative input terminal of the amplifier are connected to form a voltage follower configuration, and the clip voltage generation source is connected to the positive side of the amplifier, a voltage that cancels the temperature characteristic of the diode is superimposed on the clip voltage. Therefore, a clip voltage that compensates for the temperature characteristics of the diode can be generated.
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 the third aspect of the present invention , since the clip voltage generation means includes a plurality of amplifiers and clip voltage generation sources, different clip voltages can be separately supplied to the low temperature side and the high temperature side.
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 .

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. 6 and FIG. FIG. 6A is a diagram illustrating the CV characteristics of the MOS capacitance element. The principle of temperature compensation is schematically explained from this figure. The rise (B region) and the fall (A region) of the CV characteristic 50 of the MOS capacitor element are used with reference to the case where the voltage difference is zero. Thus, it is configured to compensate for low and high temperatures, respectively. FIG. 6B is a graph showing the relationship between the load capacity and the temperature when the MOS capacitor having the characteristics shown in FIG. 6A is used. For example, the region C is generated by a MOS capacitor element ML described later, and the region D is generated by a MOS capacitor element MH described later. As a result, the characteristics of the curve 51 can be obtained. That is, MOS capacitor elements are required for low temperature and high temperature, respectively.
FIG. 7A is a diagram showing the relationship between the high temperature compensation voltage and the temperature. That is, the high temperature compensation uses the interval between the negative potential and the potential difference 0 in the CV characteristic curve 31 of FIG. 7B, so that Vref32 and VH33 are equal (potential difference = 0), and the point P becomes the high temperature portion. Like that. The conventional compensation voltage 34 is a straight line as shown by a broken line. In this case, since the capacitance of the MOS capacitor element is variably controlled even in the temperature range, the region 29 in FIG. 7B including the Cmin portion of the CV characteristic is used, which causes the above-described problem. It was. Therefore, in order to use only the region 30 in FIG. 7B, it can be seen that it is useful to provide a voltage limit function so that the voltage is constant up to the point Q in FIG. 7A.

FIG. 1 is a block diagram showing a partial configuration of a temperature compensated piezoelectric oscillator according to a first embodiment of 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 depending on the ambient temperature, and a temperature compensation voltage generation circuit (temperature compensation voltage generation unit) that generates a voltage based on the changed parameters of 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) output from the temperature compensation voltage generation circuit 2 and the reference voltage (Vref), and temperature compensation A clip voltage generation circuit (clip voltage generation means) 5 that clips a voltage to a predetermined voltage, capacitors 7 and 9, and resistors 6, 8, and 13 are configured.
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. 5 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 opposing electrodes of ML11 and MH10 are connected is connected to a piezoelectric vibrator (quartz crystal) X and is connected to Vref via a resistor 13. In the clip voltage generation circuit 5 of this embodiment, the clip power supply Vcl2 is connected to the non-inverting input terminal of the differential amplifier 5b, the inverting input terminal and the output terminal are connected, and the anodes of the diodes 5a and 5c are connected to the output terminal. Is connected. The cathodes of the diodes 5a and 5c are connected to VH and VL, respectively. Further, the voltage of 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. Next, the operation will be described. First, the operation of circuit control based on VL20 will be described on the assumption that the temperature has continuously changed from −40 ° C. to + 90 ° C. VL20 is at the intersection R with Vref at -40 ° C., and the ML11 terminal voltage at that time is 0 V, so ML11 has a predetermined capacity within the rising range of the CV characteristics (FIG. 6A). Capacitance with zero potential difference). When the temperature rises, VL20 decreases linearly, and accordingly, the potential difference between the terminals of ML11 increases and the capacity of ML11 increases. When the voltage is near + 25 ° C., the circuit is set so that VL is lower than the clip voltage Vcl 2 of the clip voltage generation circuit 5, so that the diode 5 c of the clip voltage generation circuit 5 near + 25 ° C. becomes forward biased, It becomes the voltage of the clip voltage Vcl2. Thereafter, when the temperature rises, the output voltage VL from the compensation voltage generation circuit further decreases, but since it is clipped by the clip voltage Vcl2, VL20 at the connection point P becomes constant as shown in FIG. In the figure, the clip voltage Vcl1 and the clip voltage Vcl2 are shown as different voltages. In this example, Vcl1 = Vcl2.

Next, the operation of 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 voltage between the terminals of MH10 at that time is 0 V, so MH10 has a predetermined capacity within the rising range of the CV characteristics (FIG. 6 (a) potential difference). 0 capacity). When the temperature decreases, VH22 decreases linearly, and accordingly, the forward bias potential difference of MH10 increases and the capacitance decreases. At around + 25 ° C., by setting the circuit so that VH22 is lower than the clip voltage Vcl2 of the clip voltage generation circuit 5, the diode 5a of the clip voltage generation circuit 5 becomes forward biased and the connection point Q is equal to the voltage of the clip voltage Vcl2. Become. Thereafter, when the temperature decreases, the output voltage VH from the compensation voltage generation circuit further decreases, but since it is clipped by the clipping voltage Vcl2, VH22 at the connection point Q becomes constant as shown in FIG.
Strictly speaking, since the forward voltage of the diodes 5a and 5c has a temperature characteristic of about −2 mV / ° C., the voltage after VH · VL clipping is about 2 mV / ° C. as described in FIG. It will have temperature characteristics. Therefore, in this embodiment, an amplifier in which the diode DO is connected to the negative terminal as shown in FIG. 3 is used, the inverting input terminal and the output terminal are connected to form a voltage follower configuration, and the clip voltage Vcl2 is connected to the non-inverting input terminal. Thus, a voltage (Vcl2 + VBE) obtained by adding the forward voltage VBE (temperature characteristic) of the diode DO is generated in the output. When this voltage is applied to the diodes 5a and 5c, the diodes 5a and 5c have a temperature characteristic of (−VBE). As a result, only (Vcl2 + VBE) + (− VBE) = Vcl2 is present at the anodes of the diodes 5a and 5c. Is applied, and the temperature characteristic of the voltage across the diode D0 can cancel the temperature characteristic of the diodes 5a and 5c.

As for low temperature compensation, since the Cmax side of the MOS capacitor element is used (see FIG. 9), no major problem occurs compared to high temperature compensation using an unstable region (Cmin) of the CV characteristic. By clipping the VL as in the embodiment, the voltage near the normal temperature can be made unchanged. That is, conventionally, since the CV characteristics of the MOS capacitor itself are used (designed) to reach the saturation region near room temperature, the capacitance does not change even if VH and VL change (= stable frequency). Therefore, the voltage as shown by the broken line in FIG. 2 was used. However, in actuality, it was not a complete saturation region, or there was a case where the capacitance change (has sensitivity) occurred even near room temperature due to characteristic variations. As a result, when temperature compensation is performed as TCXO, the voltage offset adjustment as shown in FIG. 4A and the gain adjustment as shown in FIG. ) Voltage 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 circuit 5, the voltage near room temperature is clipped to a constant value, so that the capacitance (frequency) is stabilized.
FIG. 5 is a block diagram showing a partial configuration of a temperature compensated piezoelectric oscillator 110 according to the second embodiment of the present invention. The same reference numerals are assigned to the same components, and duplicate descriptions are omitted. FIG. 5 differs from FIG. 1 in that a clip voltage generation circuit 4 is added and VH and VL are individually clipped. The VH is clipped by the clip voltage generation circuit 5 as in FIG. In the clip voltage generation circuit 4 of FIG. 5, the clip power supply Vcl1 is connected in series to the plus terminal of the differential amplifier 4b, the minus terminal and the output terminal are connected, and the anode of the diode 5c is connected from the output terminal. The cathode of the diode 5c is connected to VL. Further, the voltage of the clip power source Vcl1 can be adjusted.

1 is a block diagram showing a partial configuration of a temperature compensated piezoelectric oscillator according to a first embodiment of the present invention. The figure showing the temperature characteristic of the compensation voltage of this invention. The figure which shows an example of the amplifier which incorporated the diode. The figure showing a mode that the voltage near normal temperature will change in order to perform voltage offset adjustment and Gain adjustment regarding VH and VL voltage when temperature compensation is carried out as TCXO. The block diagram which shows the partial structure of the temperature compensation type | mold piezoelectric oscillator which concerns on the 2nd Example form of this invention. 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 capacitance element. The figure showing the relation between the potential difference applied to the MOS capacitor and the capacitance. The figure explaining a mode that a characteristic changes with the temperature characteristics of a diode, when using a clip voltage generating circuit.

Explanation of symbols

1 frequency temperature compensation circuit, 2 temperature compensation voltage generation circuit, 3 temperature detection unit, 5 clip voltage generation circuit, 5a, 5c diode, 5b differential amplifier, Vcl2 clip power supply, 6, 8, 13 resistance, 7, 9 DC Capacitor for blocking, 10, 11 MOS capacitor element, X crystal resonator

Claims (4)

A piezoelectric oscillator comprising a piezoelectric vibrator excited at a predetermined frequency, an oscillation circuit, and a frequency temperature compensation circuit that compensates for a change in oscillation frequency due to a temperature change,
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 MOS capacitance element whose capacitance changes based on the potential difference between the generated temperature compensation voltage and a reference voltage, and the temperature compensation voltage within a desired temperature range, the low capacitance value region in the CV characteristic of the MOS capacitance element and a clip voltage generating means for clipping to avoid the potential difference below,
The clip voltage generation means includes a differential amplifier, a clip voltage generation source for generating a clip voltage, and a first diode provided between the output terminal of the differential amplifier and the output terminal of the frequency temperature compensation circuit, The differential amplifier includes a second diode so as to be forward-connected to the emitter of the transistor on the inverting input terminal side among the plurality of transistors constituting the differential amplifier, and the output terminal of the differential amplifier And a inverting input terminal, and the clip voltage generation source is connected to a non-inverting input terminal of the differential amplifier . The temperature compensation voltage generator includes a reference control voltage generator that generates a reference voltage having a predetermined potential, and a low-temperature control that generates a voltage that compensates for the temperature characteristics of the piezoelectric vibrator on a low temperature side centered on a normal temperature. are those having a voltage generating unit, and high-temperature control voltage generation unit for generating a voltage that compensates the temperature characteristic of the piezoelectric vibrator on the high temperature side around the room temperature, the,
The MOS capacitance element includes a low temperature portion compensation MOS capacitance element to which the output voltage of the low temperature control voltage generation portion is supplied, a high temperature portion compensation MOS capacitance element to which the output voltage of the high temperature control voltage generation portion is supplied, With
The clip voltage generating means, the output voltage and the output voltage of the high-temperature control voltage generation section of the cold control voltage generation unit, the following potential difference of the low capacitance region in C-V characteristic of the high-temperature portion compensation MOS capacitor element The temperature-compensated piezoelectric oscillator according to claim 1 , wherein the temperature-compensated piezoelectric oscillator is clipped so as not to occur. The temperature compensation voltage generator includes a reference control voltage generator that generates a reference voltage having a predetermined potential, and a low-temperature control that generates a voltage that compensates for the temperature characteristics of the piezoelectric vibrator on a low temperature side centered on a normal temperature. A voltage generator, and a high-temperature control voltage generator that generates a voltage that compensates for the temperature characteristics of the piezoelectric vibrator on the high temperature side centered on normal temperature,
The MOS capacitance element includes a low temperature portion compensation MOS capacitance element to which the output voltage of the low temperature control voltage generation portion is supplied, a high temperature portion compensation MOS capacitance element to which the output voltage of the high temperature control voltage generation portion is supplied, With
The clip voltage generating means includes: a first clip voltage generating means for clipping the output voltage of the low temperature control voltage generating section; and a second clip voltage generating means for clipping the output voltage of the high temperature control voltage generating section. It is equipped with
The second clip voltage generation means clips the output voltage of the high temperature control voltage generation unit 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 high temperature part compensation MOS capacitor. The temperature compensated piezoelectric oscillator according to claim 1 . The temperature-compensated piezoelectric oscillator according to claim 1 , wherein the clip voltage generation means can arbitrarily set a voltage value of the clip voltage generation source.

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