JP3433720B2 - Oscillation circuit - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oscillator circuit, and more particularly to a surface acoustic wave (SAW), SAW.
Abbreviated) as an oscillator.

[0002]

2. Description of the Related Art When designing an oscillator circuit, it is important to select a resonator. This is because the oscillation frequency and its temperature characteristics differ depending on the type of resonator, and the method of temperature control also differs. The resonator is a tuning fork type resonator having an oscillation frequency of several tens of KHz, and an A having an oscillation frequency of several tens of MHz.
There are a resonator made of T-cut type crystal, a resonator made of SAW having an oscillation frequency of several hundred MHz to several GHz, and the like.

When a known AT-cut resonator is used,
The oscillation frequency changes in a cubic curve with respect to the temperature change. Therefore, a stable oscillation frequency can be obtained by using a portion close to the straight line of the cubic curve.

On the other hand, SAW resonators (hereinafter,
When a SAW resonator is used), the oscillation frequency changes in a quadratic curve with respect to temperature changes. For example, as shown in FIG. 16, the oscillation frequency f _out changes in a quadratic curve with respect to the change in the temperature T. In this case, the quadratic curve in the figure changes with the temperature θ as the apex temperature. It should be noted that in reality, the curve does not become an accurate quadratic curve as shown in the figure, but the curve approximates the quadratic curve.

That is, the oscillation frequency of the oscillation circuit constructed by using the SAW resonator changes in proportion to almost the square of the temperature. That is, the frequency change rate Δf / f0 is
It can be expressed by the following equation (1).

Δf / f0 [ppm] = α (T−θ) ² (1) In the formula (1), f0 is a peak frequency, α is a frequency temperature coefficient, T is temperature, and θ is a frequency peak temperature. is there.

By the way, for the SAW oscillation circuit, there is known a technique for temperature compensation using a well-known thermistor. For example, a conventional technique for compensating for temperature characteristics is disclosed in Japanese Patent Laid-Open No. 59-59.
It is disclosed in Japanese Patent No. 74709. In this publication, the ambient temperature is detected by a thermistor, and the oscillation frequency of the oscillation circuit is controlled according to the detection result.

Further, the temperature compensation system includes an analog system and a digital system. The analog method is a method of feeding back an analog output of a temperature sensor such as a thermistor to control the temperature. On the other hand, the digital method is a method in which the feedback signal is a digital signal such as a step waveform. In this digital method, a stepped portion appears in the controlled waveform. Therefore, since there is a portion where the waveform changes abruptly, noise is generated in this portion and the noise characteristic deteriorates.

From the above, when an excellent noise characteristic is expected, the analog method is generally used.

[0010]

When temperature compensation is performed using a thermistor as described in the above-mentioned patent publications, it is not possible to reduce the size of the entire oscillator circuit, and a large mounting space is required to some extent. . As a result, there is a strong demand for downsizing, and it is difficult to compensate the temperature of the oscillation circuit mounted on a mobile terminal or the like.

The present invention has been made to solve the above-mentioned drawbacks of the prior art, and an object thereof is to provide an oscillator circuit which can improve the temperature characteristics and can be further downsized.

[0012]

An oscillation circuit according to the present invention is an oscillation circuit having a resonator whose oscillation frequency changes in a substantially quadratic curve with respect to temperature change, and whose output is It includes a temperature sensor that changes in a substantially straight line and a conversion circuit that converts the output of the sensor according to another curve whose convex direction is opposite to that of the quadratic curve, and controls the oscillation frequency according to this conversion output. It is characterized by doing so. The resonator is, for example, a surface acoustic wave element.

The conversion circuit includes an absolute value circuit for converting the output of the sensor so that the output is folded back at the predetermined temperature, and a quadratic curve circuit for converting the converted output into a quadratic curve. To do. The other curve may be a V-shaped curve that changes so that the value of the oscillation frequency turns back at a predetermined temperature, and the conversion circuit may convert the output of the sensor according to the V-shaped curve.

The quadratic curve circuit is characterized by including an inverting adder having an operational amplifier and a feedback resistor for adding the converted outputs, and a MOS transistor for controlling a current flowing through the feedback resistor.

The absolute value circuit has adjustment terminals for individually adjusting the converted output obtained by converting the output of the sensor in the frequency direction and the temperature direction. The absolute value circuit includes an inverting idealization diode circuit that receives the output of the sensor and an inverting adder that receives the output of this circuit, and the reference voltage level of the operational amplifier that constitutes them is Change it with the adjustment terminal.

Further, a predetermined power source is applied to the adjustment terminal via a resistor, and the resistor is realized by a resistor formed so as to be freely trimmed. The inverting adder has a feedback resistor, and the feedback resistor is realized by a resistor formed so as to be freely trimmed.

A plurality of resistors and a plurality of switches provided corresponding to these resistors and for controlling on / off of the electrical connection state of the corresponding resistors are provided instead of the above-mentioned trimmer formed resistors. The total resistance value may be adjusted by turning on / off these switches.
Further, in place of the trimmer-formed resistors, a plurality of resistors and a plurality of freely-cuttable wirings provided corresponding to these resistors for controlling the electrical connection state of the corresponding resistors are provided. And the total resistance value may be adjusted by cutting these wiring patterns.

The temperature sensor is characterized by being constituted by N (N is a natural number) transistors connected so that a change in output with respect to a temperature change has a linear characteristic.

In short, in this circuit, when a resonator having a temperature characteristic of a substantially quadratic curve is used, the output of the temperature sensor is converted according to another curve having a convex direction opposite to that of the above curve, and this converted output The oscillation frequency is controlled according to. By doing so, the obtained oscillation output frequency can be made almost constant regardless of the temperature change. The output of the temperature sensor may be converted according to the V-shaped curve depending on the temperature characteristics of the resonator.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. In each drawing referred to in the following description, the same parts as those in the other drawings are denoted by the same reference numerals.

FIG. 1 is a block diagram showing an embodiment of an oscillator circuit according to the present invention. As shown in the figure, the oscillation circuit according to the present embodiment has a temperature sensor 1 for detecting the ambient temperature, a conversion circuit 2 for converting the output V _T as described later, and a SAW resonator. In addition, the voltage control SAW oscillation circuit 3 whose oscillation frequency is controlled according to the compensation output V _C of the conversion circuit 2 is included. These sensors and circuits are generally configured as one module. The temperature sensor 1 is preferably arranged near the SAW resonator.

Next, the operation of the oscillation circuit will be described with reference to FIGS. In each of these figures, figure (a)
Conversion circuit the output V _T of the temperature sensor for the ambient temperature T, (b) shows an input of the output V _T of the temperature sensor 2
The output V _C of FIG. (C) the oscillation output of the SAW oscillator 3 for compensating the output V _C (hereinafter, referred to as variable characteristic), and a diagram respectively. This oscillation output may change linearly with respect to the compensation output V _C , or may change in a curve. Further, FIG. 7D is a diagram showing the temperature characteristics of the SAW oscillation circuit 3 by a broken line and the oscillation frequency finally obtained by a solid line.

First, in FIG. 2, it is assumed that the output V _T of the temperature sensor 1 changes linearly with respect to the change of the temperature T, as shown in FIG. The output having the linear characteristic is converted into a quadratic curve in the conversion circuit 2 as shown in FIG. Here, if the variable characteristic of the voltage controlled SAW oscillation circuit 3 changes linearly as shown in FIG.
When the temperature characteristic of the oscillator circuit 3 changes along the quadratic curve (broken line) in the same figure (d), the finally obtained oscillation frequency is as shown by the solid line in the same figure (d). Moreover, the value is almost constant with respect to the temperature change.

Further, in FIG. 3, it is assumed that the output V _T of the temperature sensor 1 changes linearly with respect to the change of the temperature T, as shown in FIG. The output having this linear characteristic is converted into a V-shaped curve in the conversion circuit 2 as shown in FIG. Here, if the variable characteristic of the voltage controlled SAW oscillator circuit 3 changes along a gentle curve as shown in FIG. 7C, the temperature characteristic of the SAW oscillator circuit 3 is shown in FIG. When changing along the quadratic curve (dashed line) in (d), the fluctuation amount of the oscillation frequency finally obtained is as shown by the solid line in (d) of FIG. It becomes very small.

Further, in FIG. 4, the temperature sensor 1 is
It is assumed that the output V _T changes linearly with respect to the change in the temperature T, as shown in FIG. The output having this linear characteristic is converted into a V-shaped curve in the conversion circuit 2 as shown in FIG. Here, if the variable characteristic of the voltage controlled SAW oscillation circuit 3 changes linearly as shown in FIG.
When the temperature characteristic of the oscillator circuit 3 changes along the quadratic curve (broken line) in FIG. 7D, the finally obtained fluctuation amount of the oscillation frequency is shown by the solid line in FIG. As shown above, it becomes slight with respect to the temperature change.

Referring to FIG. 2 above, the curve of the temperature characteristic of the SAW oscillation circuit 3 shown by the broken line in FIG. 2 (d) is upwardly convex, and the curve of FIG. Is a downwardly convex shape. In this way, the oscillator circuit is controlled according to the curve whose convex direction is opposite. At this time, the formulas corresponding to the curves of the temperature characteristics of the SAW oscillation circuit 3 shown by the broken line in FIG. 7D and the formulas corresponding to the output of the conversion circuit shown by the solid line have mutually different signs. It will be different. That is, in the conversion circuit, the sign of the corresponding mathematical expression is S
The output of the temperature sensor is converted according to the curve of FIG. 6B which is different from the quadratic curve which is the characteristic of the AW oscillation circuit 3. Then, temperature compensation is performed by the output V _C of this conversion circuit.

Further, referring to FIGS. 3 and 4, the curve of the temperature characteristic of the SAW oscillation circuit 3 shown by the broken line in each figure (d) has a convex shape in the upward direction. ) V
The curve is a convex shape in the downward direction. In this way, the oscillator circuit is controlled according to the curve whose convex direction is opposite. At this time, in the conversion circuit, the output of the temperature sensor is converted according to the V-shaped curve as shown in FIG. That is, the conversion circuit converts the output of the temperature sensor 1 according to the V-shaped curve that turns back at a predetermined temperature. Then, using this converted output, temperature compensation is performed for the temperature characteristic of the SAW oscillation circuit 3 shown by the broken line in each figure (d).

As the temperature sensor 1, a sensor that derives a linear output with respect to a temperature change is used. In this case, if the temperature sensor is configured by combining the transistors, the temperature sensor can be integrated on one chip.

In this case, for example, a transistor is shown in FIG.
The combination may be as shown in FIG. First, the figure
5 is a negative 1 constructed by using a MOS transistor.
A temperature sensor with a second order coefficient is shown. The same figure (a)
Power supply V as shown in _CCBetween the ground and the ground
Anti-R_a, And the gate and drain in common
And a connected MOS transistor M1. MOS
Transistor threshold voltage and channel resistance
By using the temperature characteristics of_TIs obtained
It In addition, the number of connected MOS transistors has been increased.
Two-stage MOS transistor as shown in (b)
M1 and M2 are provided or shown in FIG.
Providing three-stage MOS transistors M1 to M3
Output V due to temperature change_TLarge voltage change rate
You can do it.

Further, as shown in FIG. 6, a P-type M
The temperature sensor may be configured by combining the OS transistor M2 and the N-type MOS transistor M1. In the figure, the drain current of both transistors are the same, if the threshold voltage of the N-type MOS transistor M1 V _THN, the threshold voltage of the P-type MOS transistor M2 and _{V THP, β 1/2 (} V T - _{V SS -V THN) = β 2} /2 (V CC -V T -V THP) ... a (2). Solving for the output V _T of the equation (2), the output V _T is as shown in equation (3). V _T = {V _CC −V _THP + (β ₁ / β ₂ ) ^1/2 (V _SS −V _THN ) ² } / {(β ₁ / β ₂ ) ^1/2 +1} (3) For temperature change The sensitivity TC (V _T ) of the output V _T is as follows: TC (V _T ) = (1 / V _T ) · 1 / (β ₁ / β ₂ ) ^1/2 · [{d (−V _THP ) / dT} + (Β ₁ / β ₂ ) ^1/2 · {d (−V _THN ) / dT}] (4) In addition, in Formula (4), "d" shall show that it is a partial differential.

The sensitivity TC (V _THN ) for the N-type MOS transistor M1 has a negative temperature characteristic, and the sensitivity TC (V _THP ) for the P-type MOS transistor M2 has a positive temperature characteristic. For example, d (V _THN ) / dT = TCV _THN · V _THN = (− 0.003 ° C. ⁻¹ ) (0.8 V) = − 2.4 mV / ° C. d (V _THP ) / dT = −TCV _THP · V _THP = (− 0.003 ° C. ⁻¹ ) (0.9V) = 2.7 mV / ° C. At this time, from β = KP · W / L, β ₁ / β ₂ = KP _n W ₁ L ₂ / KP _p W ₂ L ₁ . Therefore, by appropriately setting the channel widths W ₁ and W ₂ and the lengths L ₁ and L ₂ of the transistors M1 and M2, a temperature sensor having a desired temperature characteristic can be obtained.

Further, as shown in FIG.
A temperature sensor may be constructed using polar transistors.
Yes. In general, bipolar transistor emitter-base
Forward voltage V_BEIs a negative first order with increasing temperature
It is represented by a straight line with a coefficient. Therefore, as shown in FIG.
Power supply voltage V_CCResistor R in series with _a
Transistor Q diode-connected to₁Can be connected to
And constitute a temperature sensor. Also, FIG.
As shown in FIG.₂
And Q₃To add a diode-connected transistor.
Output V for temperature change by connecting several_Tof
The rate of voltage change can be increased.

As shown in FIG. 8, the operational amplifier OP
May be used to configure the temperature sensor. When the circuit shown in the figure is assumed to have a stable operating point, the same as the voltage drop caused a voltage drop caused by the resistor R _a by a resistor R _b. Therefore, the current I ₁ and the current I ₂ are
It is determined by the ratio of the value of the resistance R _{a to} the value of the resistance R _b . Ignoring the base current, ΔV _BE = V _t ln (I ₁ / I ₂ ) · (I _S2 / I _S1 ) = V _t ln (R _b / R _a ) · (I _S2 / I _S1 ) ... (5) Becomes However, in the equation (5), V _t is a thermal voltage, I
_S1 and I _S2 are saturation currents. This voltage will be applied across the resistor R _c. Since the current flowing through the resistor R _c is equal to the current flowing through the resistor R _b, the voltage drop across the resistor R _b V
_Rb is given by equation (6). V _Rb = R _b / R _c · ΔV _BE = R _b / R _c · V _t ln (R _b / R _a ) · (I _S2 / I _S1 ) ... (6) The output V _T is applied to the resistance R _a It is the sum of the voltage and the voltage applied to the transistor Q ₁ . Since the voltage applied to the resistor R _a is equal to the voltage applied to the resistor R _b , the output V _T is given by the equation (7). V _T = V _BE1 + (R _b / R _c ) V _t · ln (R _b / R _a ) · (I _S2 / I _S1 ) = V _BE1 + KV _t (7) Generally, between the base and emitter of the transistor. Voltage V
_BE1 is represented by a straight line with a negative linear coefficient with increasing temperature. The thermal voltage V _t has a positive temperature coefficient, and the value of K in the equation (7) depends on the ratio of (R _b / R _a ), (R _b / R _c ), and (I _S2 / I _S1 ). Decided. Normally, the value of K is set so that the temperature characteristic is erased and used as a bias circuit. By properly setting the value of K, it operates as a voltage output temperature sensor.

As described above, the temperature sensor may be constructed by combining N (N is a natural number) transistors connected so that the change of the output with respect to the temperature change has a linear characteristic.

Not limited to the temperature sensors having the various configurations described above, various other temperature sensors that can be integrated may be used. If the output of the temperature sensor 1 is a current output, it may be changed to a voltage value with the configuration shown in FIG. 9, for example. That is, assuming that the current source TS in the figure is the output of the temperature sensor 1, a resistor R for flowing the current is prepared, and an output V _T as a voltage output is derived from both ends of the resistor R. good.

If necessary, an amplifier for amplifying the output of the temperature sensor 1 or an amplifier for inverting and amplifying it may be provided and the amplified output may be inputted to the conversion circuit 2.

In the voltage controlled SAW oscillator circuit 3, S
A varicap (variable capacitance diode) is generally used to control the voltage value applied to the AW resonator. For example, as shown in FIG. 10, the voltage control S
It suffices to configure the AW oscillation circuit 3 and provide the output V _C obtained by converting the output V _T of the temperature sensor 1 by the conversion circuit 2 at the connection point between the SAW resonator SAW and the varicap C _V. When the values of the resistors and the capacitances are appropriately selected, the case where the SAW oscillation circuit changes linearly and the case where the SAW oscillation circuit changes linearly depending on the varicap of the oscillation output f _out and the relationship with other capacitances due to the operation of the transistor Tr. There is. If the output of the conversion circuit is added to these, the desired characteristics can be obtained. In the figure, V _CC is a power supply.

FIG. 11 shows an internal configuration example of the conversion circuit. The conversion circuit shown in the figure includes an inverting idealization diode circuit 20 using an operational amplifier OP1 and diodes D1 and D2, and an inverting adder 21 composed of an operational amplifier OP2 and each resistor.
It operates as a well-known absolute value circuit. Furthermore, a U-shaped curve is obtained by the MOS transistor Tr1 provided at the output stage of the inverting adder 21. In this conversion circuit, a portion of the operating curve of the MOS transistor in which the current changes with the square of the voltage is used. That is, a part of the feedback current flowing through the resistor Rf is branched to the MOS transistor side, and the branched current secondarily changes according to the operation of the MOS transistor Tr, so that the feedback current also secondarily changes. It will be. That is, since the quadratic curve operation portion of the MOS transistor is used and the quadratic curve circuit that changes the feedback current according to the operation of this portion is configured, the output of the quadratic curve can be obtained.

Here, the MOS transistor T in FIG.
If the output stage circuit such as r1 is omitted and the inverting adder 22 having the configuration shown in FIG. 12 is adopted, a V-shaped curve can be obtained. That is, as shown in FIG. 13, with respect to the change in the output V _T of the temperature sensor, the compensation output V _C changes according to the V-shaped curve in the figure. That is, the output V _T of the temperature sensor 1 is folded back at the output V _H corresponding to the peak temperature. As a result, the compensation output V _C becomes V as shown in FIG.
A temperature characteristic that draws a curved line can be obtained. The left side of the V-shaped curve in the figure is the low temperature side, and the right side is the high temperature side.

Returning to FIG. 12, the compensation output V _C is expressed by V _C = (R _f / R) | V _T −V _H | + 3R _f / R · (V _V −
V _H ) + V _V. Further, the vertex coordinates of the V-shaped curve is the _{{V H, 3R f / R} · (V V -V H) + V V}, the slope of this curve, -R _f / R (low temperature side) , R _f
/ R (high temperature side).

Thus, the output of the conversion circuit 2 is
It is possible to perform temperature compensation by following a letter-shaped curve and controlling the oscillation circuit using this curve. in this case,
In order to perform temperature compensation as shown in each of FIGS. 2 to 4 (d), the output waveform of the conversion circuit is relatively moved in the temperature direction or the frequency direction, and the position of the curve is changed. It is necessary to make adjustments. In order to perform the alignment in the frequency direction and the temperature direction, the conversion circuit 2 is provided with an adjustment terminal. The adjustment terminals are the terminals V _V and V _H in FIGS. 11 and 12, and the position of the curve can be adjusted individually in the frequency direction and the temperature direction by adjusting the voltage values applied to these terminals.

[0042] In this case, the resistance R _H trimmed by adjusting the reference voltage level V _H by performing the adjusting vertices temperature direction (lateral direction), the reference voltage level V _V by trimming resistor R _V To adjust the frequency direction (vertical direction) of the apex.

By trimming the resistor R _f , the slope of the curve can be adjusted.

At this time, resistors R _H , R _V , and R _f by printing resistors are provided on the back surface of the substrate or the like, and these are trimmed with a laser or the like, or laser trimming is performed on a part of the IC package. A transparent window may be provided and trimming may be performed using this window. In these cases, trimming adjustment is performed after IC packaging. The trimming adjustment may be performed separately for each IC package, or may be performed for one lot of IC package products. In these cases, the IC package is formed after trimming adjustment.

If desired temperature characteristics can be obtained without trimming adjustment, no particular adjustment is necessary. Since trimming using a laser is a well-known technique, description thereof is omitted here. In short, this circuit adopts a configuration in which the portion to be adjusted is taken out to facilitate adjustment. Instead of adjusting the trimming, the resistance value may be digitally changed according to the digital data.

For example, as shown in FIG. 14A, switches SW _a1 to SW _a4 are provided in series in correspondence with the resistors R _{a1 to} R _a4 , and these switches are turned on / off. By doing so, a desired resistance value may be obtained. In the state shown in the figure, since only the switch SW _a1 is in the on state, only the resistor R _a1 is electrically connected. As described above, by turning on / off the switches SW _{a1 to} SW _a4 , the resistances R _H , R _V , and R _f can be set to desired resistance values. As shown in the figure, by using the resistor array and the switch group, it becomes unnecessary to use the laser trimming device.

Further, as shown in FIG.
Corresponding to each resistor R _b1 to R _b4 may be provided a pattern P _b1 to P _b4 and may be obtained a desired resistance value by these patterns trimmed or cut by a laser trimming device or the like. In the state shown in the figure, the pattern P
_Since patterns other than _b1 are cut (X in the figure
), Only the resistor R _a1 is electrically connected.
In this way, by trimming or cutting the patterns P _{b1 to} P _b4 as necessary, the resistances R _H , R _V , and R _{f can be obtained.}
Can be set to a desired resistance value.

The resistors R _{a1 to} R _a4 and the resistors R _{b1 to} R _b4 shown in FIG. 14 do not have to have the same resistance value. If necessary, they may have different resistance values. Other types of resistance values can be obtained by combining the resistance values.

Further, as shown in FIG. 15, a shortcut pattern P may be provided in advance so that only the resistor R _f serves as a feedback resistor. This inverting adder 2
If 3 is used as it is, it operates similarly to the inverting adder 22 in FIG. 12, and a V-shaped curve is obtained.

Then, in the case of performing the compensation with higher accuracy, the pattern P may be cut and the circuit of the output stage such as the transistor Tr1 may be made effective. By performing this pattern cutting, the same operation as that of the inverting adder 22 in FIG. 11 can be obtained, and highly accurate adjustment can be performed.

That is, when the pattern P is not cut, only the feedback resistor R _f serves as the feedback circuit of the inverting adder. On the other hand, if the pattern P is cut, not only the feedback resistor R _f but also the resistor R1 and the transistor Tr1 become a part of the feedback circuit of the inverting adder.

As described above, the pattern P for short-circuiting the feedback circuit is provided in advance, and the pattern P is cut as needed, whereby the circuit configuration can be changed so that more accurate adjustment can be performed. Of. On the other hand, when the pattern is not cut, the circuit configuration does not require highly accurate adjustment. That is, the performance of the oscillation circuit can be easily determined and the degree of temperature compensation can be easily changed depending on whether or not pattern cutting is performed. Products that have undergone pattern cutting work can be adjusted with high precision, and products that have not been subjected to work can be adjusted to a normal degree, so product lineup configurations can be easily realized. can do.

Although the oscillation circuit using the SAW as the resonator has been described above, the present invention is not limited to this, and the oscillation frequency changes in a substantially quadratic curve with respect to temperature change.
It is obvious that the present invention can be widely applied to an oscillation circuit using another element having the next temperature characteristic as a resonator.

That is, according to the present invention, in the resonator having the second-order temperature characteristic, the voltage corresponding to the peak temperature of the resonator is adjusted to the characteristic of the resonator to be adjusted in the state of the oscillation circuit. Can be done.

With regard to the description of the claims, the present invention can have the following aspects.

(1) The oscillation frequency is approximately 2 with respect to the temperature change.
An oscillating circuit having a resonator that changes along a quadratic curve, wherein a temperature sensor whose output changes in a substantially straight line with respect to a change in temperature, and a corresponding mathematical expression have a sign different from that of the quadratic curve. And a conversion circuit for converting the output of the sensor according to the curve, and the oscillation frequency of the resonator is controlled according to the conversion output.

(2) The oscillator circuit according to claim 3, wherein the quadratic curve circuit changes the feedback current to the feedback resistor according to the operation of the quadratic curve portion of the transistor.

(3) The oscillator circuit according to claim 3, further comprising a pattern for short-cutting the quadratic curve circuit, the pattern being cuttable.

[0059]

As described above, the present invention uses a temperature sensor having a linear temperature characteristic composed of a transistor or the like instead of a thermistor, and controls the oscillation frequency according to the output of the temperature sensor, thereby making the entire oscillation circuit. There is an effect that can be reduced.

The oscillation frequency is approximately 2 with respect to the temperature change.
For a resonator that changes by drawing a quadratic curve, the output of the sensor is converted according to another curve whose convex direction is opposite to that of the quadratic curve, and the oscillating frequency is controlled according to this converted output. There is an effect that it is possible to suppress the fluctuation amount of.

Furthermore, by providing an adjusting terminal for matching the temperature characteristic of the resonator with the curve after the output of the temperature sensor is converted, the temperature compensation can be performed with higher accuracy. .

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an oscillator circuit according to the present invention.

FIG. 2 is a characteristic diagram showing an example of temperature compensation by the oscillation circuit of FIG.

FIG. 3 is a characteristic diagram showing another example of temperature compensation by the oscillation circuit of FIG.

FIG. 4 is a characteristic diagram showing another example of temperature compensation by the oscillation circuit of FIG.

FIG. 5 is a diagram showing a configuration example of a temperature sensor.

FIG. 6 is a diagram showing another configuration example of a temperature sensor.

FIG. 7 is a diagram showing still another configuration example of the temperature sensor.

FIG. 8 is a diagram showing another configuration example of the temperature sensor.

FIG. 9 is a diagram showing a circuit for converting a temperature sensor output to a voltage output when the output is a current output.

10 is a diagram showing a configuration example of a voltage control SAW oscillation circuit in FIG.

11 is a diagram showing a configuration example of a conversion circuit in FIG.

12 is a diagram showing another configuration example of the conversion circuit in FIG.

13 is a diagram showing an example of a compensation output in the conversion circuit in FIG.

FIG. 14A is a diagram showing an example of a resistor array and a switch group provided in place of the trimming resistor, and FIG. 14B is a diagram showing an example of a resistor array provided in place of the trimming resistor and a cutting pattern. .

15 is a diagram showing another configuration example of the conversion circuit in FIG.

FIG. 16 is a diagram showing that the oscillation frequency changes along a quadratic curve with respect to temperature change.

[Explanation of symbols]

1 Temperature sensor 2 conversion circuit 3 Voltage control SAW oscillator circuit 20 Inversion idealized diode circuit 21-23 Inverting adder SAW SAW resonator

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-7-231221 (JP, A) JP-A-1-284002 (JP, A) JP-A-10-284938 (JP, A) JP-A-11- 64394 (JP, A) JP-A-9-107239 (JP, A) JP-A-58-205886 (JP, A) JP-A-10-135756 (JP, A) JP-A-10-270941 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H03B 5/30-5/36

Claims (2)

(57) [Claims] 1. An oscillation circuit having a surface acoustic wave resonator whose oscillation frequency changes in a substantially quadratic curve with respect to temperature change, wherein the output changes in a substantially straight line with respect to temperature change. A sensor and an absolute value circuit for converting the output of the sensor so as to turn back the output at the predetermined temperature according to another curve whose convex direction is opposite to that of the quadratic curve, and a conversion output from the absolute value circuit. Change output to quadratic curve
And a conversion circuit for converting , wherein the conversion circuit includes an operational amplifier and at least two or more.
The absolute value circuit having a feedback resistor composed of a resistor.
An inverting adder for adding the converted outputs output from
MOS transistor that controls the current flowing through the feedback resistor
And the drain of the MOS transistor is connected to the feedback resistor.
Connected to a node divided by
The source of the transistor is grounded through a resistor,
The gate of the OS transistor receives the output of the inverting adder.
The voltage obtained by voltage division is applied and output from the conversion circuit.
An oscillating circuit characterized in that the oscillating frequency is controlled according to the converted output applied. 2. The N temperature sensors are connected so that the change of the output with respect to the temperature change has a linear characteristic.
Is a natural number transistor, and the oscillator circuit according to claim 1.