WO2020066672A1

WO2020066672A1 - Temperature compensation circuit and temperature compensated crystal oscillator

Info

Publication number: WO2020066672A1
Application number: PCT/JP2019/035978
Authority: WO
Inventors: 有継矢島
Original assignee: 株式会社村田製作所
Priority date: 2018-09-28
Filing date: 2019-09-12
Publication date: 2020-04-02

Abstract

A temperature compensation circuit, including: a compensation circuit for generating, on the basis of a temperature signal sensed by a temperature sensor, a compensation signal, which is minimum at a first temperature and maximum at a second temperature higher than the first temperature; a correction circuit for generating a correction signal for correcting the compensation signal at a first temperature range and/or a second temperature range, the first temperature range being between the first temperature and a third temperature inclusive, the third temperature being between the first temperature and the second temperature, the second temperature range being between a fourth temperature and the second temperature inclusive, the fourth temperature being between the first temperature and the second temperature; and a temperature compensation signal circuit for applying a control signal to a frequency-variable-type crystal oscillator, the control signal being applied on the basis of a corrected compensation signal, which is the compensation signal after being corrected by the correction signal.

Description

Temperature compensation circuit and temperature compensated crystal oscillator

The present invention relates to a temperature compensation circuit and a temperature compensated crystal oscillator.

The quartz crystal oscillator (Crystal Resonator) included in the crystal oscillator (Crystal Oscillator) changes its resonance frequency according to the temperature. A temperature-compensated crystal oscillator (Temperature Compensated crystal Oscillator, hereinafter sometimes referred to as “TCXO”) may be a voltage-controlled crystal oscillator (Voltage Control Crystal Oscillator, hereinafter referred to as “VCXO”) depending on the temperature. Has a temperature compensation circuit for generating a voltage to be applied to. This temperature compensation circuit can control the oscillation frequency of the temperature compensated crystal oscillator to be constant even if the temperature changes.

The following Patent Document 1 describes a temperature-compensated piezoelectric oscillator of an analog circuit type.

JP-A-11-261336

A temperature-compensated crystal oscillator including a crystal vibrating element having a frequency temperature characteristic similar to a cubic curve, having a local maximum value at a first temperature and a local minimum value at a second temperature higher than the first temperature. A signal for canceling an ideal waveform (hereinafter, sometimes referred to as a “model waveform”) of the frequency temperature characteristic of the vibrating element is applied to a variable frequency crystal oscillator. As a result, the oscillation frequency is controlled to be constant.

In order to increase the degree of approximation of the waveform of the frequency temperature characteristic of the actual crystal vibrating element to the model waveform, approximation using a higher-order mathematical expression may be considered. If the order of the approximate expression is increased, the waveform can be approximated in principle. However, in the analog circuit system, in order to realize a higher-order expression, more circuit configurations are required. If the number of circuit configurations increases, errors in each circuit may accumulate, and errors in the entire analog circuit may increase.

The present invention has been made in view of the above problems, and an object of the present invention is to appropriately suppress a temperature change of an oscillation frequency.

The temperature compensation circuit according to one aspect of the present invention includes a crystal vibrating element having a frequency temperature characteristic in which a resonance frequency becomes a maximum at a first temperature and a resonance frequency becomes a minimum at a second temperature higher than the first temperature. A low-temperature compensation circuit that outputs a current that substantially changes in a temperature range lower than the first temperature as a first compensation signal, and a second temperature equal to or higher than the first temperature. An intermediate temperature compensation circuit that outputs a current that changes substantially as a second compensation signal, and a high temperature compensation circuit that outputs a current that changes substantially in a temperature range higher than the second temperature as a third compensation signal And a compensation circuit that generates a compensation signal that is minimum at a first temperature and maximum at a second temperature, based on a temperature signal of the temperature sensor, and a first temperature or more, and a first temperature and a reference. Warm A first correction circuit that outputs a first correction signal that corrects the first compensation signal in a first temperature range that is equal to or lower than a third temperature, and a fourth temperature that is equal to or higher than a fourth temperature between a reference temperature and a second temperature. In addition, a correction circuit including only a second correction circuit that outputs a second correction signal for correcting the third compensation signal in a second temperature range equal to or lower than the second temperature, and a first correction signal corrected by the first correction signal. A frequency-variable type based on a first corrected compensation signal that is a compensation signal, a second compensation signal, and a second compensated compensation signal that is a third compensation signal corrected by the second compensation signal. A temperature compensation signal circuit for applying a control signal to the crystal oscillator.

According to the present invention, it is possible to preferably suppress the temperature change of the oscillation frequency.

FIG. 2 is a diagram illustrating a configuration of a temperature-compensated crystal oscillator according to an embodiment. FIG. 4 is a diagram showing a relationship between temperature and frequency deviation of AT-cut quartz. FIG. 3 is a diagram illustrating a configuration of a current-voltage conversion circuit of the temperature compensated crystal oscillator according to the embodiment. FIG. 3 is a diagram illustrating a configuration of a compensation circuit and a correction circuit of the temperature-compensated crystal oscillator according to the embodiment. FIG. 4 is a diagram illustrating characteristics of a low-temperature compensation circuit of the temperature-compensated crystal oscillator according to the embodiment. FIG. 4 is a diagram illustrating characteristics of a medium temperature compensation circuit of the temperature compensated crystal oscillator according to the embodiment. FIG. 4 is a diagram illustrating characteristics of a high-temperature compensation circuit of the temperature-compensated crystal oscillator according to the embodiment. FIG. 3 is a diagram illustrating characteristics of a compensation circuit of the temperature compensated crystal oscillator according to the embodiment. FIG. 4 is a diagram illustrating characteristics of a compensation circuit and a correction circuit of the temperature-compensated crystal oscillator according to the embodiment. FIG. 3 is a diagram illustrating a correction principle of the temperature compensated crystal oscillator according to the embodiment. FIG. 3 is a diagram illustrating a correction principle of the temperature compensated crystal oscillator according to the embodiment. FIG. 3 is a diagram illustrating a correction principle of the temperature compensated crystal oscillator according to the embodiment. FIG. 3 is a diagram illustrating a correction principle of the temperature compensated crystal oscillator according to the embodiment.

Hereinafter, embodiments of the temperature compensation circuit and the temperature compensation crystal oscillator of the present invention will be described in detail with reference to the drawings. The present invention is not limited by the embodiment. Each embodiment is an exemplification, and it goes without saying that the configurations shown in the different embodiments can be partially replaced or combined. From the second embodiment onward, description of matters common to the first embodiment will be omitted, and only different points will be described. In particular, the same operation and effect of the same configuration will not be sequentially described for each embodiment.

FIG. 1 is a diagram showing a configuration of a temperature-compensated crystal oscillator (TCXO) 1 according to an embodiment. The TCXO 1 includes a frequency variable crystal oscillator 2, a temperature sensor 3, and a temperature compensation circuit 4. The variable frequency crystal oscillator 2 is a voltage controlled crystal oscillator (VCXO) 2.

The VCXO 2 includes a crystal resonator 11, a resistor 12 as a feedback resistor, an inverter (inverting) circuit 13 as an amplifier, a variable capacitance circuit 14, and a capacitor 15. The crystal resonator element 11 includes an AT-cut crystal blank and excitation electrodes provided on both main surfaces of the crystal blank. The variable capacitance circuit 14 is a variable capacitance diode (varicap). The present disclosure is not limited to variable capacitance diodes. Specifically, the variable capacitance circuit 14 is composed of a plurality of capacitors, the connection state of one or more capacitors on the basis of a control voltage V ₂ to be described later may be selected.

(4) The crystal resonator 11, the resistor 12, and the inverter circuit 13 are connected in parallel. The variable capacitance circuit 14 is connected between one end of the crystal resonator 11 and a reference potential. The reference potential is exemplified by a ground potential, but the present disclosure is not limited to this. The capacitor 15 is connected between the other end of the crystal resonator 11 and a reference potential. Note that the capacitor 15 may be replaced with a variable capacitance circuit. In this case, the replaced variable capacitance circuit is connected to the temperature compensation circuit 4.

The crystal vibrating element 11 has a characteristic that the resonance frequency changes according to the temperature. Hereinafter, the ideal waveform 100 represented by the frequency temperature characteristic may be referred to as a “model waveform”. The frequency temperature characteristic of the crystal resonator element 11 used in the VCXO 2, specifically, as shown in FIG. 2, the waveform indicating the change in the resonance frequency deviation with respect to the temperature change of the AT-cut crystal resonator element 11 has a maximum temperature T. _1, the temperature T ₅ showing a higher minimum than the temperature T _1, which is similar to waveform tertiary curve exists.

Therefore, the temperature compensation circuit 4, to offset the change in the frequency-temperature characteristics of the crystal resonator element 11, applying a control voltage V ₂ to stabilize the frequency-temperature characteristic VCXO2. Control voltage V ₂ has a temperature T ₁ of which shows the minimum, and the temperature T ₅ showing the maximum, the output waveform similar to the tertiary curve exists. In order to control the frequency temperature characteristic constant in the temperature compensation circuit 4, thereby reducing the control voltage V ₂ applied to VCXO2 with an increase in the resonant frequency. Control waveform of the control voltage V ₂ is compared with the model waveform shown in FIG. 2, it is shown in the vertical axis direction by inverting the waveform. Temperature T ₁ is, corresponds to the "first temperature" in the present disclosure, the temperature T ₅ corresponds to the "second temperature" in the present disclosure. The temperature T ₁ is, for example, a temperature of −20 ° C. or more and −10 ° C. or less, for example, −15 ° C., but the present disclosure is not limited thereto. Temperature T ₅ are, 65 ° C. or higher 75 ° C. below the temperature, for example 70 ° C. is exemplified, the present disclosure is not limited thereto.

(4) The capacitance of the variable capacitance circuit 14 changes. When the capacitance of the variable capacitance circuit 14 changes, the time constant of the VCXO2 changes, so that the oscillation frequency of the VCXO2 changes. The temperature compensating circuit 4 cancels the temperature change of the oscillation frequency of the VCXO2 by the change of the time constant of the VCXO2. The temperature compensating circuit 4 includes an analog circuit that reproduces an ideal waveform of a change in resonance frequency with respect to a change in temperature in the crystal resonator element 11, and generates a signal that suppresses a temperature change in the oscillation frequency of the VCXO2 based on the ideal waveform. The temperature compensation circuit 4 can control the oscillation frequency of the VCXO2 to be constant.

(4) The temperature sensor 3 is disposed near the crystal vibrating element 11 to detect a temperature, and outputs a voltage Vtemp representing a temperature state to the temperature compensation circuit 4. The voltage Vtemp corresponds to the “temperature signal” of the present disclosure.

The temperature compensation circuit 4 includes a compensation circuit 5, a correction circuit 6, and a temperature compensation signal circuit 7. Note that the temperature compensation circuit 4 is configured by an analog element.

The compensation circuit 5 includes a low temperature compensation circuit 21, a medium temperature compensation circuit 22, and a high temperature compensation circuit 23. In the present disclosure, a low temperature, a lower temperature range than the temperature T _1. The medium temperature, and the temperature above T ₁ and the temperature T ₅ less temperature range is intended to include a reference temperature T _3. Reference temperature T ₃ is a temperature serving as a reference for the oscillation frequency of VCXO2, the temperature of 25 ° C. or higher 30 ° C. or less is exemplified, the present disclosure is not limited thereto. For example, the reference temperature _{T 3} may be 27 ° C. (300 Kelvin). Reference temperature T ₃ may be a center temperature of the temperature above T ₁ and the temperature T ₅ less temperature range. In the present disclosure, a high temperature, a higher temperature range than the temperature T _5.

Cold compensation circuit 21 outputs a current _{I 1} is a signal for temperature compensation of VCXO2 at low temperatures. Current I ₁ corresponds to the "first compensation signal" of the present disclosure.

Medium temperature compensation circuit 22 outputs a current _{I 2} is a signal for temperature compensation of VCXO2 at moderate temperatures. Current I ₂ corresponds to the "second compensation signal" of the present disclosure.

Hot compensation circuit 23 outputs a current _{I 3} is a signal for temperature compensation of VCXO2 at high temperatures. Current I _3, corresponding to the "third compensation signal" of the present disclosure.

Output terminals of the low-temperature compensation circuit 21, the medium-temperature compensation circuit 22, and the high-temperature compensation circuit 23 are connected by wiring. Therefore, the current I ₁ , the current I _2, and the current I ₃ are added to become the current I _SUM1 . The current I _SUM1 corresponds to the “compensation signal” of the present disclosure.

The correction circuit 6 includes a first correction circuit 31 and a second correction circuit 32.

The first correction circuit 31, the range of temperature above _{T 1} and temperature _{T 2} below the temperature, and outputs a current _{I 4} is a signal for correcting the current _{I SUM1.} Here, temperature _{T 2} is a temperature lower than the high and the reference temperature _{T 3} than the temperature _{T 1.} For temperature _{T 2} will be described later. Temperature T ₂ corresponds to the "third temperature" of the present disclosure. Current I ₄ corresponds to the "first correction signal" of the present disclosure.

The second correction circuit 32, a range of temperature _{T 4} or more and a temperature _{T 5} temperature below, and outputs a current _{I 5} is a signal for correcting the current _{I SUM1.} Here, the temperature _{T 4} is high and lower than the temperature _{T 5} temperature than the reference temperature _{T 3.} Temperature _{T 4} will be described later. Temperature T ₄ corresponds to a "fourth temperature" of the present disclosure. Current I ₅ corresponds to the "second correction signal" of the present disclosure.

Output terminals of the first correction circuit 31 and the second correction circuit 32 are connected by wiring. Therefore, the current I ₄ and the current I ₅ are added to become the current I _SUM2 . The current I _SUM2 corresponds to the “correction signal” of the present disclosure. The current I _SUM1 and the current I _SUM2 are added by the wiring connection, and become the current I _SUM3 . The current _ISUM3 is input to the temperature compensation signal circuit 7. The current I _SUM3 corresponds to the “compensation signal after correction” of the present disclosure.

In the embodiment, for the sake of easy understanding, the current I ₁ , the current I _2, and the current I ₃ are added to form a current I _SUM1 , and the current I ₄ and the current I ₅ are added to form a current I _SUM2 , Although the current I _SUM1 and the current I _SUM2 are added to obtain the current I _SUM3 , the present disclosure is not limited to this. For example, the output terminals of the low temperature compensation circuit 21, the medium temperature compensation circuit 22, the high temperature compensation circuit 23, the first correction circuit 31, and the second correction circuit 32 may be connected by wiring. That is, the current I ₁ , the current I ₂ , the current I ₃ , the current I _4, and the current I ₅ may be added at one time to obtain the current I _SUM3 .

The temperature compensation signal circuit 7 includes a current-voltage conversion circuit 41 and an adjustment circuit 42.

FIG. 3 is a diagram showing a configuration of a current-voltage conversion circuit of the temperature compensated crystal oscillator according to the embodiment. The current-voltage conversion circuit 41 includes an operational amplifier 41a, a constant voltage source 41b, and

resistors

41c and 41d.

A constant voltage is input to the non-inverting input terminal of the operational amplifier 41a from the constant voltage source 41b. One end of the resistor 41c is connected to the inverting input terminal of the operational amplifier 41a. The current _ISUM3 is input to the other end of the resistor 41c. The resistor 41d is connected between the inverting input terminal and the output terminal of the operational amplifier 41a. That is, the current-voltage conversion circuit 41 is an inverting amplifier circuit. From the output terminal of the operational amplifier 41a, a current - voltage V ₁ of the post-voltage conversion, and output to the adjustment circuit 42.

Adjusting circuit 42 outputs the control voltage V ₂ obtained by multiplying the gain K set in advance in the voltages V ₁ to the variable capacitance circuit 14, an amplification circuit. The gain K will be described later. Note that the adjustment circuit 42 is not limited to an amplifier circuit. Adjusting circuit 42, in addition to multiplying the gain K to voltages V _1, the voltages V ₁ may perform other processing.

For example, the adjustment circuit 42, as the center values of the voltages V ₁ at the reference temperature T _3, may be rotated waveforms of voltages V _1. This adjustment circuit 42, by multiplying the large gain in voltages _{V 1} as the temperature of VCXO2 away from the reference temperature _{T 3,} can be realized. Further, for example, the adjustment circuit 42, or by offsetting the waveform of the voltages V ₁ in the frequency direction may be or is offset a waveform of voltages V ₁ to a temperature direction. Adjusting circuit 42, at least, it is sufficient that multiplying the gain K to the voltage V _1. By performing these processes, the adjustment circuit 42 can appropriately control the fluctuation of the resonance frequency even if the VCXO2 has an individual difference (for example, manufacturing variation of the cut angle of the AT cut).

FIG. 4 is a diagram illustrating a configuration of a compensation circuit and a correction circuit of the temperature-compensated crystal oscillator according to the embodiment. The low-temperature compensation circuit 21 includes N-channel transistors Tr1 and Tr2, and a circuit 51.

The collector of the transistor Tr1 is connected to the power supply potential VDD. The base of the transistor Tr1, the threshold voltage Vth ₁ is input. The emitter of the transistor Tr1 is connected to the emitter of the transistor Tr2.

The collector of the transistor Tr2 outputs a current _{I 1.} Note that the actual collector current of the transistor Tr2 flows in the collector. However, as described above, the current-voltage conversion circuit 41 is an inverting amplification circuit. Accordingly, for easy understanding, the direction of the current I ₁ is set to a direction flowing out from the collector of the transistor Tr2. When the direction of flow out the direction of the current I ₁ from the collector of the transistor Tr2, a current - voltage converting circuit 41 can be considered replaced with a non-inverting amplifier circuit.

電圧 A voltage Vtemp representing the temperature of VCXO2 is input to the base of the transistor Tr2. The emitter of the transistor Tr2 is connected to the emitter of the transistor Tr1.

In the present disclosure, each transistor is a bipolar transistor, but the present disclosure is not limited to this. Each transistor may be a field effect transistor (Field Effect Transistor: FET). However, the FET has more phase noise than the bipolar transistor. Therefore, from the viewpoint of suppressing phase noise, a bipolar transistor is preferable. However, from the viewpoints of suppressing cost, mounting area, and low power consumption, FETs are preferable.

The circuit 51 includes an N-channel transistor 51a, a resistor 51b, and a constant voltage source 51c.

(4) The collector of the transistor 51a is connected to the emitters of the transistors Tr1 and Tr2. A constant voltage is input to the base of the transistor 51a from a constant voltage source 51c. The resistor 51b is connected between the emitter of the transistor 51a and a reference potential. That is, the circuit 51 is a constant current circuit for flowing a constant current. Therefore, the circuit 51 keeps the sum of the emitter current of the transistor Tr1 and the emitter current of the transistor Tr2 constant.

{That is, the low-temperature compensation circuit 21 is an emitter-coupled amplifier (source-coupled amplifier).

Cold compensating circuit 21 are the emitter-coupled amplifying circuit (source-coupled amplifier circuit), a current I ₁ is expressed by the following equation (1). In the formula (1), α _F is the current gain of the transistors Tr1 and Tr2 (base grounded). I _EE is the sum of the emitter current of the transistor Tr1 and the emitter current of the transistor Tr2. _VT is the thermal voltage. In the low-temperature compensation circuit 21, Vid = Vth ₁ -Vtemp.

The current I ₁ substantially changes around the threshold voltage Vth ₁ when the Vid is approximately in the range of −4 V _T to 4 V _T. The current I ₁ is substantially constant when Vid is approximately −4 V _T or less. Current _{I 1} is in a range Vid is more than 4V _T generally is substantially zero.

FIG. 5 is a diagram illustrating characteristics of the low-temperature compensation circuit of the temperature-compensated crystal oscillator according to the embodiment. Waveform 101 represents the current _{I 1.} Current I ₁ shows normalized. The threshold voltage Vth _1, as in the current I ₁ becomes substantially zero at a temperature above T _1, are set. That is, the current I ₁ is substantially varied at a low temperature, no change in the medium temperature and high temperature.

Referring again to FIG. 4, the intermediate temperature compensation circuit 22 includes N-channel transistors Tr3 and Tr4 and a circuit 51.

The collector of the transistor Tr3 is connected to the power supply potential VDD. The base of the transistor Tr3, the threshold voltage Vth ₂ is input. The emitter of the transistor Tr3 is connected to the emitter of the transistor Tr4.

The collector of the transistor Tr4 outputs a current _{I 2.} The direction of the current I _2, similar to the current I _1, and the direction flowing out from the collector of the transistor Tr4.

(4) A voltage Vtemp representing the temperature of VCXO2 is input to the base of the transistor Tr4. The emitter of the transistor Tr4 is connected to the emitter of the transistor Tr3.

That is, the intermediate temperature compensation circuit 22 is an emitter-coupled amplifier (source-coupled amplifier).

Medium temperature compensating circuit 22 are the emitter-coupled amplifying circuit (source-coupled amplifier circuit), the current I ₂ is expressed by the following equation (2). In the intermediate temperature compensation circuit 22, Vid = Vth ₂ −Vtemp.

The current I ₂ substantially changes around the threshold voltage Vth ₂ when the Vid is approximately in the range of −4 V _T to 4 V _T. The current I ₂ becomes substantially zero when the Vid is approximately −4 V _T or less. Current _{I 2} is in the range Vid is more than 4V _T generally substantially constant.

FIG. 6 is a diagram illustrating characteristics of the intermediate temperature compensation circuit of the temperature compensation crystal oscillator according to the embodiment. Waveform 102 represents the current _{I 2.} Current I ₂ illustrates normalized. Waveform 102 of the current _{I 2} (soaring), compared with the waveform 101 of the current _{I 1} (downward-sloping), it is inverted. Threshold voltage Vth _2, together with the current I ₂ is substantially zero at temperatures T ₁ or less, so that the current I ₂ is substantially constant at a temperature T ₅ or more, are set. That is, the current I ₂ is substantially varied at moderate temperatures and does not change at low and high temperatures. Temperature represented by the threshold voltage Vth _2, for example, may be a reference temperature _{T 3.}

Referring again to FIG. 4, the high-temperature compensation circuit 23 includes N-channel transistors Tr5 and Tr6, and a circuit 51.

The collector of the transistor Tr5 is connected to the power supply potential VDD. The base of the transistor Tr5, the threshold voltage Vth ₃ is input. The emitter of the transistor Tr5 is connected to the emitter of the transistor Tr6.

The collector of the transistor Tr6 outputs a current _{I 3.} The direction of the current I _3, similar to the current I _1, and the direction flowing out from the collector of the transistor Tr6.

電圧 A voltage Vtemp representing the temperature of VCXO2 is input to the base of the transistor Tr6. The emitter of the transistor Tr6 is connected to the emitter of the transistor Tr5.

{That is, the high-temperature compensation circuit 23 is an emitter-coupled amplifier (source-coupled amplifier).

Hot compensating circuit 23 are the emitter-coupled amplifying circuit (source-coupled amplifier circuit), a current I ₃ is represented by the formula (1) described above. In the high temperature compensation circuit 23, Vid = Vth ₃ -Vtemp. The current I ₃ substantially changes with the Vid about the threshold voltage Vth ₃ within a range of approximately −4 V _T to 4 V _T. Current _{I 3,} in the following ranges Vid is almost -4 V _T, is substantially constant. Current _{I 3,} in the range Vid is more than 4V _T generally is substantially zero.

In the embodiment, each of the low-temperature compensation circuit 21, the medium-temperature compensation circuit 22, and the high-temperature compensation circuit 23 is an emitter-coupled amplifier (source-coupled amplifier), but the present disclosure is not limited to this. Each of the low-temperature compensation circuit 21, the medium-temperature compensation circuit 22, and the high-temperature compensation circuit 23 may be another amplification circuit or a circuit other than the amplification circuit.

FIG. 7 is a diagram illustrating characteristics of the high-temperature compensation circuit of the temperature-compensated crystal oscillator according to the embodiment. Waveform 103 represents the current _{I 3.} Current I ₃ shows normalized. Threshold voltage Vth _3, like current I ₃ is substantially constant at a temperature T ₅ less, and is set. That is, the current I ₃ is substantially varied at a high temperature, it does not change at low and moderate temperatures.

FIG. 8 is a diagram illustrating characteristics of a compensation circuit of the temperature compensated crystal oscillator according to the embodiment. Waveform 104 represents current I _SUM1 .

Cold In (a temperature range lower than the temperature _{T 1),} the current _{I 2} (waveform 102) is substantially zero, the current _{I 3} (waveform 103) is substantially "1". Therefore, current _{I SUM1} (waveform 104) is such as to shift by "1" current _{I 1} (waveform 101) in the positive direction.

In medium temperature (temperature above _{T 1} and the temperature _{T 5} less temperature range), the current _{I 1} (waveform 101) is substantially zero, the current _{I 3} (waveform 103) is substantially in the "1" . Therefore, current _{I SUM1} (waveform 104) is such as to shift by "1" current _{I 2} (waveform 102) in the positive direction.

High temperature in (a temperature range higher than the temperature _{T 5),} the current _{I 1} (waveform 101) is substantially zero, the current _{I 2} (waveform 102) is substantially "1". Therefore, current _{I SUM1} (waveform 104) is such as to shift by "1" current _{I 3} (waveform 103) in the positive direction.

That is, the current _{I SUM1} (waveform 104) becomes a minimum at a temperature _{T 1,} the maximum temperature _{T 5.}

Note that the temperature compensation range of the TCXO1 is a range of the temperature T ₀ or more and the temperature T ₆ or less. The temperature T ₀ is exemplified to be lower than the temperature T ₁ and in a range in which the current I ₁ (waveform 101) changes, but the present disclosure is not limited to this. The temperature T ₆ is exemplified to be higher than the temperature T ₅ and in a range where the current I ₃ (waveform 103) changes, but the present disclosure is not limited to this.

By the temperature compensation range TCXO1 a temperature T ₀ or more and the temperature T ₆ the range, it is possible below. Cold compensation circuit 21, since it is not necessary to consider the temperature lower than the temperature T _0, the various values (parameter, e.g., gain, etc. of the transistors Tr1 and Tr2) by adjusting the, at low temperatures, the waveform 104 model It can be adjusted to the waveform with high accuracy. Similarly, the high-temperature compensation circuit 23, since it is not necessary to consider the temperature higher than the temperature T _6, by adjusting the various values, at high temperatures, can be aligned with high precision waveform 104 in model waveform.

However, it has been found that when the waveform 104 is accurately matched to the model waveform at low and high temperatures, a difference (error) occurs between the waveform 104 and the model waveform at medium temperatures. Specifically, the cold end of the range of medium temperature, i.e., at a temperature above T ₁ and temperature T ₂ below the first temperature range 111, the difference (error) is generated between the waveform and the model waveform of the current I _SUM1 Was found. Similarly, the high temperature end of the range of medium temperature, i.e., at a second temperature range 112 of the temperature T ₄ or more and a temperature T ₅ less, the difference (error) between the waveform and the model waveform of the current I _SUM1 occur Was found.

Therefore, the first correction circuit 31 is provided to correct the current I _SUM1 in the first temperature range 111. Similarly, the second correction circuit 32 is provided to correct the current I _SUM1 in the second temperature range 112. Temperature _{T 2,} by comparing the waveform and model waveform of the current _{I SUM1,} is predetermined. Also, the magnitude of the current I ₄ is at the first temperature range 111, depending on the magnitude of the difference (error) between the waveform and the model waveform of the current I _SUM1, is predetermined.

Similarly, the temperature _{T 4,} by comparing the waveform and model waveform of the current _{I SUM1,} is predetermined. Also, the magnitude of the current _{I 5,} i.e., the size of the transistors Tr9 and Tr10 are in the second temperature range 112, depending on the magnitude of the difference (error) between the waveform and the model waveform of the current _{I SUM1,} predetermined Can be

In the embodiment, the correction circuit 6 includes both the first correction circuit 31 and the second correction circuit 32, but the present disclosure is not limited to this. For example, if the upper limit of the temperature compensation range TCXO1 is lower than the temperature _{T 4,} there is no need to correct the current _{I SUM1} by the second temperature range 112, the second correction circuit 32 is not required. For example, when the lower limit of the temperature compensation range TCXO1 is higher than the temperature _{T 2,} it is not necessary to correct the current _{I SUM1} at a first temperature range 111, the first correction circuit 31 is not required. That is, the correction circuit 6 only needs to include at least one of the first correction circuit 31 and the second correction circuit 32.

Referring again to FIG. 4, the first correction circuit 31 includes N-channel transistors Tr7 and Tr8 and a circuit 51.

The collector of the transistor Tr7 is connected to the power supply potential VDD. The base of the transistor Tr7, the threshold voltage Vth ₄ is input. The emitter of the transistor Tr7 is connected to the emitter of the transistor Tr8.

The collector of the transistor Tr8 outputs a current _{I 4.} The direction of the current I _4, similar to the current I _1, and the direction flowing out from the collector of the transistor Tr8.

電圧 A voltage Vtemp representing the temperature of VCXO2 is input to the base of the transistor Tr8. The emitter of the transistor Tr8 is connected to the emitter of the transistor Tr7.

That is, the first correction circuit 31 is an emitter-coupled amplifier (source-coupled amplifier).

The transistor Tr7 corresponds to the “first transistor” of the present disclosure. The transistor Tr8 corresponds to the “second transistor” of the present disclosure. The threshold voltage Vth ₄ corresponds to the “first threshold voltage” of the present disclosure.

The first correction circuit 31 are the emitter-coupled amplifying circuit (source-coupled amplifier circuit), the current I ₄ is represented by the equation (2). In the first correction circuit 31, Vid = Vth ₄ −Vtemp. The current I ₄ substantially changes around the threshold voltage Vth ₄ when the Vid is approximately in the range of −4 V _T to 4 V _T. Current _{I 4} is in the following range Vid is almost -4 V _T, becomes substantially zero. Current _{I 4} is in the range Vid is more than 4V _T generally substantially constant.

The second correction circuit 32 includes N-channel transistors Tr9 and Tr10 and a circuit 51.

The collector of the transistor Tr9 is connected to the power supply potential VDD. The base of the transistor Tr9, the threshold voltage Vth ₅ is input. The emitter of the transistor Tr9 is connected to the emitter of the transistor Tr10.

The collector of the transistor Tr10 outputs a current _{I 5.} The direction of the current _{I 5,} as in the current _{I 1,} and the direction flowing out from the collector of the transistor Tr10.

電圧 A voltage Vtemp representing the temperature of VCXO2 is input to the base of the transistor Tr10. The emitter of the transistor Tr10 is connected to the emitter of the transistor Tr9.

{That is, the second correction circuit 32 is an emitter-coupled amplifier (source-coupled amplifier).

The transistor Tr9 corresponds to the “third transistor” of the present disclosure. The transistor Tr10 corresponds to a “fourth transistor” of the present disclosure. Threshold voltage Vth ₅ corresponds to the "second threshold voltage" of the present disclosure.

The second correction circuit 32 are the emitter-coupled amplifying circuit (source-coupled amplifier circuit), a current I ₅ is represented by the formula (1) described above. In the second correction circuit 32, Vid = Vth ₅ -Vtemp. The current I ₅ substantially changes with the Vid approximately in the range of −4 V _T to 4 V _T around the threshold voltage Vth ₅ . Current _{I 5} is in the range Vid is generally less -4 V _T, is substantially constant. Current _{I 5} is in the range Vid is more than 4V _T generally is substantially zero.

Note that the transistors Tr7 to Tr10 are smaller in size than the transistors Tr1 to Tr6. That is, each of the currents I ₄ and I ₅ is smaller than each of the currents I ₁ to I ₃ . The size of each transistor can be adjusted, for example, by changing the number of fingers.

The size of the transistors Tr7 and Tr8, i.e., the magnitude of the current _{I 4} is at the first temperature range 111, depending on the magnitude of the difference (error) between the waveform and the model waveform of the current _{I SUM1,} is predetermined.

The size of the transistors Tr9 and Tr10, i.e., the magnitude of the current _{I 5} is in the second temperature range 112, depending on the magnitude of the difference (error) between the waveform and the model waveform of the current _{I SUM1,} is predetermined.

In the embodiment, each of the first correction circuit 31 and the second correction circuit 32 is an emitter-coupled amplifier (source-coupled amplifier), but the present disclosure is not limited to this. Each of the first correction circuit 31 and the second correction circuit 32 may be another amplifier circuit or a circuit other than the amplifier circuit.

Hereinafter, a case where the first correction circuit 31 corrects the current I _SUM1 in the first temperature range 111 will be described. The case where the second correction circuit 32 corrects the current I _SUM1 in the second temperature range 112 is the _same as the case where the first correction circuit 31 corrects the current I _SUM1 in the first temperature range 111. Description is omitted.

FIG. 9 is a diagram illustrating characteristics of a compensation circuit and a correction circuit of the temperature-compensated crystal oscillator according to the embodiment. Waveform 105 represents the current _{I 4.} Waveform 108 represents current I _SUM3 . As described above, the first correction circuit 31 are the emitter-coupled amplifying circuit (source-coupled amplifier circuit), a waveform 105 of the current I ₄ is a soaring.

Current I ₄ is the lower temperature range than the temperature T ₁ (low temperature), it becomes substantially zero. Current I ₄ is a temperature range higher than the temperature T ₂ is substantially constant. That is, the threshold voltage Vth ₄ is set at the center of the first temperature range 111.

Current I ₄ is the lower temperature range than the temperature T ₁ (low temperature), since substantially be zero, it does not affect the shape of the waveform of the current I _SUM1. That is, at low temperatures, waveform 108 (current I _SUM3 ) matches waveform 104 (current I _SUM1 ).

Current _{I 4} is the temperature above _{T 1} and temperature _{T 2} below the first temperature range 111, so varies substantially, affects the shape of the waveform of the current _{I SUM1.} That is, in the first temperature range 111, the shape of the waveform 108 (current I _SUM3 ) is different from the shape of the waveform 104 (current I _SUM1 ).

Current I ₄ is a temperature T ₂ above temperature range is substantially constant. That is, at temperature _{T 2} above temperature range, the shape of the waveform 108 (current _{I SUM3)} is the same as the shape of the waveform 104 (current _{I SUM1).} However, the waveform 108 is obtained by offsetting the waveform 104 by the offset amount 121 in the positive direction. Offset 121 is the same as the current _{I 4.}

Incidentally, for easy understanding, the current I ₄ is stressed, are largely shown. The actual value of the current I ₄ is less than the value shown.

In temperature _{T 2} above temperature range, the waveform 108 (current _{I SUM3)} is offset amount 121 waveform 104 (current _{I SUM1)} in the positive direction, becomes offset. The inventor has found that the effect of the offset amount 121 can be suppressed by multiplying the voltage V ₁ (current I _SUM3 ) by the gain K in the adjustment circuit 42.

Hereinafter, the principle that the influence of the offset amount 121 can be suppressed by multiplying the gain V by the voltage V ₁ (current I _SUM3 ) will be described.

FIG. 10 to FIG. 13 are diagrams for simplifying and explaining the correction principle of the temperature compensated crystal oscillator according to the embodiment. In FIG. 10, a model waveform 131 is an example of a waveform obtained by simplifying the frequency temperature characteristics of the crystal resonator 11. The compensation waveform 132 is an example of the waveform of the compensation circuit. In FIG. 10, _{x 0} corresponds to the temperature _{T 1,} _{x 2} corresponds to the temperature _{T 2.}

The function of the model waveform 131 is represented by the following equation (3).
y = f (x) [x ₀ ≦ x ≦ x ₂ ] (3)
The function of the compensation waveform 132 is represented by the following equation (4) as a linear function for simplification.
y = g (x) = x [x ₀ ≦ x ≦ x ₂ ] (4)
The difference between the model waveform 131 and the compensation waveform 132 is defined as Δy.

y ₀ = g (x ₀ ) = x ₀ , y ₁ = g (x ₁ ) = x ₁ , and y ₂ = g (x ₂ ) = x ₂ .

11, a difference waveform 133 is a difference Δy between the model waveform 131 and the compensation waveform 132. Δy, at _{x 0,} 0, in the vicinity of _{x 1} (slightly positive than _{x 1),} a maximum, in _{x 2,} 0.

In FIG. 11, a correction waveform 134 is an example of a correction circuit waveform. The function of the correction waveform 134 is represented by the following equation (5).
y = Δg (x) [x ₀ ≦ x ≦ x ₂ ] (5)
Here, Δg (x) is simplified by the following equations (6) and (7).
y = Δg (x) = x [x ₀ ≦ x <x ₁ ] (6)
y = Δg (x) = x ₁ [x ₁ ≦ x ≦ x ₂ ] (7)

In FIG. 12, a composite waveform 135 is an example of a composite waveform obtained by adding the correction waveform 134 to the compensation waveform 132.
The function of the composite waveform 135 is represented by the following equation (8).
y = g (x) + Δg (x) [x ₀ ≦ x ≦ x ₂ ] (8)

y = g (x) + Δg (x) is expressed by the following equations (9) and (10).
y = g (x) + Δg (x) = 2x [x ₀ ≦ x <x ₁ ] (9)
y = g (x) + Δg (x) = x + x ₁ [x ₁ ≦ x ≦ x ₂ ] (10)

Here, in order to eliminate the deviations in _{x 2} in the synthesized waveform 135 and the model waveform 131, the composite waveform 135, it is multiplied by a gain K, to obtain a control signal Ref. That is, the control signal Ref is represented by the following equation (11).
Ref = K (g (x) + Δg (x)) (11)

Here, at an arbitrary coordinate x ₃ (x ₃ ≧ x ₂ ), the gain K is predetermined so that f (x ₃ ) = K (g (x ₃ ) + Δg (x ₃ )). That is, the gain K is predetermined by the following equation (12).
K = f (x ₃ ) / (g (x ₃ ) + Δg (x ₃ )) (12)

For example, f (x ₃ ) = x ₃ . Also, g (x ₃ ) + Δg (x ₃ ) = x ₃ + x ₁ . Therefore, the gain K has the value of the following equation (13).
K = x ₃ / (x ₃ + x ₁ ) (13)

For _example, it is _{f (x1) = 2x 1 ·} K = 2x 3 x 1 / (x 3 + x 1).

In FIG. 13, the control waveform 136 is an example of a waveform for explaining the principle of the waveform of the control signal Ref. That is, the control waveform 136 is an example of a waveform for explaining the principle of generating a waveform of the control signal Ref after multiplying the composite waveform 135 by the gain K. That is, a control waveform 136 obtained by multiplying the composite waveform 135 obtained by adding the correction waveform 134 to the compensation waveform 132 and the gain K is obtained. As shown in FIG. 13, the difference between the control waveform 136 and the model waveform 131 is smaller than the difference between the compensation waveform 132 and the model waveform 131. That is, it can be seen that the shape of the control waveform 136 is closer to the model waveform 131 than the shape of the compensation waveform 132.

If the above-described simplified principle of generating the control signal used for the temperature compensation is applied, the first correction circuit 31 outputs the current I ₄ (the principle is described with the correction waveform 134 in FIG. 11), and the adjustment circuit 42 , _Multiply the value of the current I _SUM3 after the current-voltage conversion by the gain K. As a result, as shown in FIG. 13, the temperature compensating circuit 4 controls the control waveform 136, which is an example of the simplified waveform of the control voltage V ₂ , in the first temperature range 111 and the frequency in the crystal vibrating element 11. The difference (error) from the model waveform 131 which is an example of the waveform whose temperature characteristic is simplified can be suitably reduced, and the change in the resonance frequency of the crystal resonator element 11 can be suitably suppressed. The first correction circuit 31, a simple circuit configuration that emitter-coupled amplifying circuit (see FIG. 4), it is possible to output a current I _4.

In the above, the case where the first correction circuit 31 corrects the current I _SUM1 in the first temperature range 111 by outputting the current I ₄ has been described. Similarly, the second correction circuit 32, by outputting the current _{I 5,} corrects the current _{I SUM1} in a second temperature range 112. Current I ₅ is substantially changed in the second temperature range 112, substantially unchanged in other temperature ranges. That is, the threshold voltage Vth ₅ is in the middle of the second temperature range 112 is set. Then, similarly to the above, the adjustment circuit 42 multiplies the value of the current I _SUM3 after the current-voltage conversion by the gain K. Thus, the temperature compensating circuit 4, in the second temperature range 112, and suitably suppressed the difference (error) between the waveform and the model waveform of the control voltage V _2, suitably suppresses the change in the oscillation frequency of VCXO2 be able to. The second correction circuit 32, a simple circuit configuration that emitter-coupled amplifying circuit (see FIG. 4), it is possible to output the current I _5.

Further, each of the low-temperature compensation circuit 21, the medium-temperature compensation circuit 22, the high-temperature compensation circuit 23, the first correction circuit 31, and the second correction circuit 32 has the same circuit configuration (in the embodiment, the emitter-coupled amplifier (source-coupled amplifier)). ), It is easy to realize the temperature compensation circuit 4 on a semiconductor integrated circuit device with an analog circuit configuration.

Note that the above-described embodiments are intended to facilitate understanding of the present invention, and are not intended to limit the present invention. The present invention may be changed / improved without departing from the spirit thereof, and the present invention also includes equivalents thereof.

DESCRIPTION OF SYMBOLS 1 Temperature-compensated crystal oscillator 2 Variable-frequency crystal oscillator 3 Temperature sensor 4 Temperature-compensation circuit 5 Compensation circuit 6 Correction circuit 7 Temperature-compensation signal circuit 11 Quartz-

vibration element

12, 41c, 41d, 51b Resistance 13 Inverter circuit 14 Variable capacitance circuit 15 Capacitor 21 Low temperature compensation circuit 22 Medium temperature compensation circuit 23 High temperature compensation circuit 31 First correction circuit 32 Second correction circuit 41 Current-voltage conversion circuit 41a

Operational amplifier

41b, 51c Constant voltage source 42 Adjustment circuit 51a, Tr1, Tr2, Tr3, Tr4, Tr5, Tr6, Tr7, Tr8, Tr9, Tr10 Transistor

Claims

A circuit for performing temperature compensation of a variable-frequency crystal oscillator including a crystal resonator having a frequency temperature characteristic in which a resonance frequency becomes maximum at a first temperature and a resonance frequency becomes minimum at a second temperature higher than the first temperature. So,
A low-temperature compensation circuit that outputs a current that substantially changes in a temperature range lower than the first temperature as a first compensation signal; and a current that substantially changes in a temperature range between the first temperature and the second temperature. A medium temperature compensation circuit that outputs a second compensation signal; and a high temperature compensation circuit that outputs a current that changes substantially in a temperature range higher than the second temperature as a third compensation signal. A compensating circuit that generates a compensation signal that is minimum at the first temperature and maximum at the second temperature based on the signal.
A first correction circuit that outputs a first correction signal for correcting the first compensation signal in a first temperature range equal to or higher than the first temperature and equal to or lower than a third temperature between the first temperature and the reference temperature; A second correction circuit that outputs a second correction signal for correcting the third compensation signal in a second temperature range between a fourth temperature between the reference temperature and the second temperature and equal to or lower than the second temperature. A correction circuit consisting of
A first compensation signal, which is the first compensation signal compensated by the first compensation signal, a second compensation signal, and the third compensation signal compensated by the second compensation signal; A temperature-compensated signal circuit for applying a control signal to the variable-frequency crystal oscillator based on a certain second corrected compensation signal;
Comprising,
Temperature compensation circuit.
The temperature compensation circuit according to claim 1,
The first correction circuit includes:
A first transistor having a first threshold voltage input to the base and a collector electrically connected to a power supply potential;
A second transistor having a base to which the temperature signal is input, an emitter electrically connected to an emitter of the first transistor, and outputting the first correction signal from a collector;
A constant current circuit for making a sum of an emitter current of the first transistor and an emitter current of the second transistor constant;
including,
Temperature compensation circuit.
The temperature compensation circuit according to claim 1,
The second correction circuit includes:
A third transistor having a second threshold voltage input to the base and a collector electrically connected to a power supply potential;
A fourth transistor having the base inputted with the temperature signal, an emitter electrically connected to the emitter of the third transistor, and outputting the second correction signal from a collector;
A constant current circuit for making the sum of the emitter current of the third transistor and the emitter current of the fourth transistor constant;
including,
Temperature compensation circuit.
The temperature compensation circuit according to claim 1, wherein:
The first correction circuit includes:
Outputting a current that substantially changes in the first temperature range and does not substantially change outside the first temperature range as the first correction signal;
Temperature compensation circuit.
The temperature compensation circuit according to claim 4,
The first correction circuit includes:
Amplifier circuit,
Temperature compensation circuit.
The temperature compensation circuit according to claim 5,
The first correction circuit includes:
An emitter-coupled amplifier circuit,
Temperature compensation circuit.
The temperature compensation circuit according to claim 1, wherein:
The second correction circuit includes:
Outputting, as the second correction signal, a current that substantially changes in the second temperature range and does not substantially change outside the second temperature range;
Temperature compensation circuit.
The temperature compensation circuit according to claim 7, wherein
The second correction circuit includes:
Amplifier circuit,
Temperature compensation circuit.
The temperature compensation circuit according to claim 8, wherein
The second correction circuit includes:
An emitter-coupled amplifier circuit,
Temperature compensation circuit.
The temperature compensation circuit according to claim 1, wherein:
Each of the low temperature compensation circuit, the medium temperature compensation circuit and the high temperature compensation circuit,
A fifth transistor having each base input with a threshold voltage, and a collector electrically connected to a power supply potential;
A sixth transistor having the base inputted with the temperature signal, an emitter electrically connected to an emitter of the fifth transistor, and outputting a compensation signal from a collector;
A constant current circuit for making the sum of the emitter current of the fifth transistor and the emitter current of the sixth transistor constant;
including,
Temperature compensation circuit.
The temperature compensation circuit according to claim 10, wherein
Each of the low temperature compensation circuit, the medium temperature compensation circuit and the high temperature compensation circuit is an amplifier circuit,
Temperature compensation circuit.
The temperature compensation circuit according to claim 11, wherein
Each of the low temperature compensation circuit, the medium temperature compensation circuit and the high temperature compensation circuit is an emitter-coupled amplifier circuit.
Temperature compensation circuit.
The temperature compensation circuit according to claim 1, wherein:
The temperature compensation signal circuit,
An adjustment circuit that outputs the control signal by multiplying at least a predetermined gain by the first corrected compensation signal, the second compensation signal, and the second corrected compensation signal,
Temperature compensation circuit.
The temperature compensation is performed on a frequency-variable type crystal oscillator including an AT-cut crystal vibrating element having a frequency temperature characteristic in which the resonance frequency becomes maximum at the first temperature and becomes minimum at the second temperature higher than the first temperature. A circuit,
A low-temperature compensation circuit that outputs a current that substantially changes in a temperature range lower than the first temperature as a first compensation signal; and a current that substantially changes in a temperature range between the first temperature and the second temperature. A medium temperature compensation circuit that outputs a second compensation signal; and a high temperature compensation circuit that outputs a current that changes substantially in a temperature range higher than the second temperature as a third compensation signal. A compensating circuit that generates a compensation signal that is minimum at the first temperature and maximum at the second temperature based on the signal.
A first correction circuit that outputs a first correction signal for correcting the first compensation signal in a first temperature range equal to or higher than the first temperature and equal to or lower than a third temperature between the first temperature and the reference temperature; A second correction circuit that outputs a second correction signal for correcting the third compensation signal in a second temperature range between a fourth temperature between the reference temperature and the second temperature and equal to or lower than the second temperature. A correction circuit consisting of
The first compensation signal, which is the first compensation signal after being compensated by the first compensation signal, is the first compensation signal, the second compensation signal, and the third compensation signal, which is compensated by the second compensation signal. A temperature-compensated signal circuit for applying a control signal to the variable-frequency crystal oscillator based on a certain second corrected compensation signal;
Comprising,
Temperature compensation circuit.
A frequency variable type crystal oscillator including a crystal vibrating element having a frequency temperature characteristic in which a resonance frequency becomes maximum at a first temperature and a resonance frequency becomes minimum at a second temperature higher than the first temperature;
A temperature sensor that outputs a temperature signal,
A low-temperature compensation circuit that outputs a current that substantially changes in a temperature range lower than the first temperature as a first compensation signal; and a current that substantially changes in a temperature range between the first temperature and the second temperature. A medium-temperature compensation circuit that outputs a second compensation signal; and a high-temperature compensation circuit that outputs a current that substantially changes in a temperature range higher than the second temperature as a third compensation signal. A compensation circuit that generates a compensation signal that is minimum at the first temperature and maximum at the second temperature,
A first correction circuit that outputs a first correction signal for correcting the first compensation signal in a first temperature range equal to or higher than the first temperature and equal to or lower than a third temperature between the first temperature and the reference temperature; A second correction circuit that outputs a second correction signal for correcting the third compensation signal in a second temperature range between a fourth temperature between the reference temperature and the second temperature and equal to or lower than the second temperature. A correction circuit consisting of
A first compensation signal, which is the first compensation signal compensated by the first compensation signal, a second compensation signal, and the third compensation signal compensated by the second compensation signal; A temperature-compensated signal circuit for applying a control signal to the variable-frequency crystal oscillator based on a certain second corrected compensation signal;
Comprising,
Temperature compensated crystal oscillator.
A frequency-variable crystal oscillator including an AT-cut crystal vibrating element having a frequency temperature characteristic in which a resonance frequency becomes maximum at a first temperature and a resonance frequency becomes minimum at a second temperature higher than the first temperature;
A temperature sensor that outputs a temperature signal,
A low-temperature compensation circuit that outputs a current that substantially changes in a temperature range lower than the first temperature as a first compensation signal; and a current that substantially changes in a temperature range between the first temperature and the second temperature. A medium-temperature compensation circuit that outputs a second compensation signal; and a high-temperature compensation circuit that outputs a current that substantially changes in a temperature range higher than the second temperature as a third compensation signal. A compensation circuit that outputs a compensation signal that is minimum at the first temperature and maximum at the second temperature,
A first correction circuit that outputs a first correction signal for correcting the first compensation signal in a first temperature range equal to or higher than the first temperature and equal to or lower than a third temperature between the first temperature and the reference temperature; A second correction circuit that outputs a second correction signal for correcting the third compensation signal in a second temperature range between a fourth temperature between the reference temperature and the second temperature and equal to or lower than the second temperature. A correction circuit consisting of
A first compensation signal, which is the first compensation signal compensated by the first compensation signal, a second compensation signal, and the third compensation signal compensated by the second compensation signal; A temperature-compensated signal circuit for applying a control signal to the variable-frequency crystal oscillator based on a certain second corrected compensation signal;
Comprising,
Temperature compensated crystal oscillator.