JP2013162259A - Piezoelectric oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric oscillator that implements high frequency and frequency stabilization on the basis of a reflection characteristic of a reflective element, and implements stable oscillation by relaxing starting conditions in accordance with characteristics of the reflective element.SOLUTION: The piezoelectric oscillator is so constructed that a transistor 1 has a gate connected with an LC resonance circuit comprising a parallel connection of a coil (L1) 2 and a capacitor (C1) 3, a drain connected with an output terminal 10, to which a supply voltage (Vcc) is applied, and a source connected with a piezoelectric resonator 5 as a reflective element, and that a variable capacitance diode 7 is connected in parallel with the LC resonator, and the variable capacitance diode 7 has a cathode side connected to the gate of the transistor 1 and fed with the supply voltage (Vcc) applied via a time constant circuit comprising a resistance (R4) 8 and a capacitor (C2) 9.

Description

  The present invention relates to a piezoelectric oscillator using a reflective element, and in particular, a piezoelectric device capable of achieving high frequency and frequency stabilization using the reflective characteristics of the reflective element, and capable of stably oscillating according to the characteristics of the reflective element. It relates to an oscillator.

[Conventional technology]
Piezoelectric oscillators include Colpitts type and Pierce type circuits.
Conventional oscillators control the frequency using a circuit that oscillates by controlling the phase of the resonator.
Regarding a conventional piezoelectric oscillator, a crystal oscillator circuit of a Colpitts circuit and a crystal oscillator circuit of an inverter circuit will be described.

[Colpitts-type crystal oscillation circuit: Fig. 5]
A conventional Colpitts crystal oscillation circuit will be described with reference to FIG. FIG. 5 is a circuit diagram of a conventional Colpitts crystal oscillation circuit.
In the conventional Colpitts-type crystal oscillation circuit, as shown in FIG. 5, one end of the crystal resonator X is connected to the base of the oscillation transistor Tr, and the other end of the crystal resonator X is grounded.
A power supply voltage V is applied to the collector of the transistor Tr via a resistor Rc, and an output terminal (OUTPUT) is provided via a capacitor.
The emitter of the transistor Tr is grounded via a resistor RE.

A power supply voltage V is applied to the base of the transistor Tr via a resistor RA, and the base is grounded via a resistor RB.
Further, one end of the series connection of the capacitors C1 and C2 is connected to the base, the other end is grounded, and a point between the capacitors C1 and C2 is connected to the emitter.
The oscillation operation is performed by the conventional Colpitts type crystal oscillation circuit having the above configuration.

[Inverter type crystal oscillation circuit: Fig. 6]
A conventional inverter type crystal oscillation circuit will be described with reference to FIG. FIG. 6 is a circuit diagram of a conventional inverter type crystal oscillation circuit.
As shown in FIG. 6, the conventional inverter type crystal oscillation circuit has one end of the crystal unit X connected to the input side of the inverter IC, the other end of the crystal unit X connected to the output side of the inverter IC, The input side and the output side are connected via a resistor RF.

One end of the capacitor Cg is connected to the input side, the other end is grounded, one end of the capacitor Cd is connected to the output side, the other end is grounded, and an output terminal (OUTPUT) is provided on the output side. ing.
The oscillation operation is performed by the conventional inverter type crystal oscillation circuit having the above configuration.

[Related technologies]
As related prior art, Japanese Patent Application Laid-Open No. 10-112612 “High Frequency Oscillation Circuit” (Murata Manufacturing Co., Ltd., Patent Document 1), Japanese Patent Application Laid-Open No. 05-304175 “Field Effect Transistor, High Frequency Signal Oscillator and Frequency Conversion Circuit” (NEC Corporation, Patent Document 2), Japanese Patent Laid-Open No. 10-242755, “Microwave Oscillator” (Murata Manufacturing Co., Ltd., Patent Document 3), Japanese Patent Laid-Open Publication No. 2006-42010, “High Frequency Oscillation Circuit, High Frequency Device, And characteristic adjustment method of high-frequency oscillation circuit "(Murata Manufacturing Co., Ltd., Patent Document 4), Japanese Unexamined Patent Application Publication No. 2001-085947," Colpitts Crystal Oscillation Circuit "(Toyo Communication Equipment Co., Ltd., Patent Document 5), Japanese Patent Application Laid-Open No. 2002-246842. No. “Microwave Oscillator” (Alps Electric Co., Ltd., Patent Document 6).

Patent Document 1 discloses that an oscillation condition is set by an output filter in a high-frequency oscillation circuit.
Patent Document 2 describes that a band reflection type oscillator includes two or more gate pads (gate terminals) and sets oscillation conditions and output matching conditions separately.

Patent Document 3 describes that in a microwave oscillator, a transistor is mounted on a microstrip line, and an inner conductor of a dielectric coaxial resonator is brought close to a predetermined position of the microstrip line via an extraction electrode. Yes.
Patent Document 4 describes that, in a high-frequency oscillation circuit, an open stub for adjusting characteristics is provided on the drain end side of an FET that connects a resonance circuit and an amplifier circuit, and characteristics are adjusted by trimming or addition of a dielectric chip. ing.

In Patent Document 5, in a crystal oscillator, a piezoelectric oscillator is connected to the emitter side, the output of the SC-cut crystal resonator is fed back, and the negative resistance at the same time as the oscillator is secured by connecting to the base via a capacitor. It is described to do.
Patent Document 6 describes that in a microwave oscillator, a dielectric resonator is controlled using a varactor diode and input to the base side.
Further, Non-Patent Document 1 describes an example of a reflective oscillator.

Japanese Patent Laid-Open No. 10-112612 Japanese Patent Laid-Open No. 05-304175 Japanese Patent Laid-Open No. 10-242755 JP 2006-42010 A JP 2001-085947 A JP 2002-246842 A

INTERNATIONAL STANDARD, Waveguide type dielectric resonators Part 2: Guidelines for oscillator and filter applications, IEC 61338-2, First edition 2004-05, International Electrotechnical Commission.

  However, in the conventional piezoelectric oscillator, the wavelength becomes shorter as the frequency becomes higher. Therefore, it is necessary to consider the line length of the printed circuit board, the line length from the resonator to the package, and the deviation when the resonator is mounted. In addition, since the line length is shifted due to these, the frequency is shifted from a desired frequency, and the phase adjustment becomes sensitive to adjust the frequency, which makes it difficult to achieve high stability.

  The present invention has been made in view of the above circumstances, and it is possible to achieve high frequency and frequency stabilization using the reflection characteristics of the reflection element, and further, the start-up conditions are relaxed and stabilized according to the characteristics of the reflection element. An object of the present invention is to provide a piezoelectric oscillator that can oscillate.

  The present invention for solving the problems of the conventional example is a piezoelectric oscillator including a transistor, and an LC resonator having a parallel-connected coil and a first capacitor is connected to a gate of the transistor, and the transistor A power supply voltage is applied to the drain of the transistor, a piezoelectric resonator as a reflective element is connected to the source of the transistor, an output terminal is provided on the drain side of the transistor, a varicap diode is connected in parallel to the LC resonator, The cathode side of the varicap diode is connected to the gate of the transistor, and a power supply voltage is applied to the cathode side via a time constant circuit.

  According to the present invention, in the piezoelectric oscillator, a second capacitor is connected to the anode side of the varicap diode, a third capacitor is connected to the cathode side of the varicap diode, and the cathode side of the varicap diode is connected to the third side. A time constant circuit is connected to a point between the capacitor and the capacitor.

  The present invention for solving the problems of the conventional example is a piezoelectric oscillator including a transistor, and an LC resonator having a coil connected in parallel and a first capacitor is connected to the gate of the transistor. A power supply voltage is applied to the drain of the transistor, a piezoelectric resonator as a reflective element is connected to the source of the transistor, an output terminal is provided on the drain side of the transistor, and in series with the first capacitor of the LC resonator The varicap diode is connected, the cathode side of the varicap diode is connected to the gate of the transistor, and the power supply voltage is applied to the cathode side through a time constant circuit.

  According to the present invention, in the piezoelectric oscillator, a fourth capacitor is connected to the cathode side of the varicap diode, and a time constant circuit is connected to a point between the cathode side of the varicap diode and the fourth capacitor. It is characterized by that.

  According to the present invention, in the piezoelectric oscillator, the time constant circuit includes a resistor having one end connected to the cathode side of the varicap diode and the other end connected to the power supply voltage, and between the resistor and the cathode side of the varicap diode. And a fifth capacitor having one end connected to this point and the other end grounded.

  According to the present invention, there is provided a piezoelectric oscillator including a transistor, wherein an LC resonator having a parallel-connected coil and a first capacitor is connected to a gate of the transistor, and a power supply voltage is applied to a drain of the transistor. A piezoelectric resonator as a reflective element is connected to the source of the transistor, an output terminal is provided on the drain side of the transistor, a varicap diode is connected in parallel to the LC resonator, and the cathode side of the varicap diode is the gate of the transistor And a piezoelectric oscillator in which a power supply voltage is applied to the cathode side via a time constant circuit. Therefore, the reflection characteristics of the reflective element are used to increase the frequency and stabilize the frequency, and the piezoelectric resonator The LC resonator capacity can be varied over a wide range according to the characteristics, and the start-up conditions can be relaxed to oscillate stably. Bets can be, there is an effect capable of improving the versatility as possible corresponding to various piezoelectric resonator.

  According to the present invention, there is provided a piezoelectric oscillator including a transistor, wherein an LC resonator having a parallel-connected coil and a first capacitor is connected to a gate of the transistor, and a power supply voltage is connected to a drain of the transistor. Applied, a piezoelectric resonator as a reflective element is connected to the source of the transistor, an output terminal is provided on the drain side of the transistor, and a varicap diode is connected in series to the first capacitor of the LC resonator. Since the cathode side of the diode is connected to the gate of the transistor and the power supply voltage is applied to the cathode side via a time constant circuit, the high frequency and frequency stabilization are achieved using the reflection characteristics of the reflective element. At the same time, the capacitance of the LC resonator can be varied within a specific range according to the characteristics of the piezoelectric resonator, There is an effect that it is possible to stably oscillate in the sum.

1 is a circuit diagram of a piezoelectric oscillator according to a first embodiment of the present invention. It is a circuit diagram of the piezoelectric oscillator which concerns on the 2nd Embodiment of this invention. It is a circuit diagram of the piezoelectric oscillator which concerns on the 3rd Embodiment of this invention. It is a circuit diagram of the piezoelectric oscillator which concerns on the 4th Embodiment of this invention. It is a circuit diagram of a conventional Colpitts type crystal oscillation circuit. It is a circuit diagram of a conventional inverter type crystal oscillation circuit.

Embodiments of the present invention will be described with reference to the drawings.
[Outline of the embodiment]
In the piezoelectric oscillator according to the embodiment of the present invention, the LC resonance circuit is connected to the gate of the transistor, the output terminal is connected to the drain, the power supply voltage is applied to the output terminal side, the reflective element is connected to the source, In addition, a varicap diode is connected in parallel to the LC resonance circuit, and the varicap diode is connected to the power supply voltage via a time constant circuit. The reflection characteristics of the reflective element are used to increase the frequency and stabilize the frequency. At the same time, the voltage applied to the varicap diode is gradually changed according to the time constant, so that the resonance frequency of the LC resonance circuit can be adjusted in a wider range according to the characteristics of the reflective element, and the oscillation is stably performed. In addition, it is possible to deal with various reflecting elements and improve versatility.

  Also, in the piezoelectric oscillator according to the embodiment of the present invention, the LC resonant circuit is connected to the gate of the transistor, the output terminal is connected to the drain, the power supply voltage is applied to the output terminal side, and the reflective element is connected to the source In addition, a varicap diode is connected in series with the capacitor of the LC resonance circuit, and the varicap diode is connected to the power supply voltage via a time constant circuit. While stabilizing the frequency, the voltage applied to the varicap diode is gradually changed according to the time constant, and the resonance frequency of the LC resonance circuit can be finely adjusted within a specific range according to the characteristics of the reflective element. It can oscillate stably.

[Piezoelectric Oscillator of First Embodiment: FIG. 1]
A piezoelectric oscillator according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a circuit diagram of a piezoelectric oscillator according to a first embodiment of the present invention.
As shown in FIG. 1, the piezoelectric oscillator (first piezoelectric oscillator) according to the first embodiment of the present invention includes a transistor 1, a coil (L1) 2, and a capacitor (C1) as basic components. 3, a resistor (R 2) 4 serving as an impedance, a piezoelectric resonator 5 as a reflection element, a resistor (R 3) 6, and an output terminal (OUTPUT) 10, and further, as a characteristic part of the first piezoelectric oscillator , A varicap diode 7, a resistor (R 4) 8, and a capacitor (C 2) 9.

[Basic Components of Piezoelectric Oscillator of Embodiment]
First, basic components of the first piezoelectric oscillator will be described. This basic component is common to the second to fourth embodiments described later.
The coil (L1) 2 and the capacitor (C1) 3 are connected in parallel to constitute an LC resonator, and perform an oscillation operation at a frequency. The capacitor (C1) 3 corresponds to the first capacitor recited in the claims.

The transistor 1 is a field effect transistor (FET) and amplifies the oscillation frequency. An output terminal 10 is connected to the drain (D) of the transistor 1, a piezoelectric resonator 5 as a reflective element is connected to the source (S), and a coil (L1) 2 and a capacitor (C1) are connected to the gate (G). 3 is connected to one end of the LC resonator.
The other end of the LC resonator is grounded via a resistor (R2) 4.
A power supply voltage is applied to the output terminal 7 side via a resistor (R3) 6.

  The transistor 1 may be an NPN transistor instead of the FET transistor. In this case, the gate of the NPN transistor operates as the base of the FET transistor, the drain operates as the collector, and the source operates as the emitter.

The piezoelectric resonator 5 of the reflection element resonates using reflection characteristics.
Specifically, by resonating the piezoelectric resonator 5 as a reflective element, the frequency can be stabilized at a high frequency.

  In the basic components described above, oscillation occurs when the oscillation frequency of the LC resonator composed of the coil (L1) 2 and the capacitor (C1) 3 is equal to the resonance frequency of the piezoelectric resonator 5 that is a reflection element. It is activated.

  The oscillation frequency is determined by the element constants of the coil (L 1) 2 and the capacitor (C 1) 3 constituting the LC resonator and the characteristics of the piezoelectric resonator 5, and is usually matched to the resonance characteristics of the mounted piezoelectric resonator 5. Thus, it is configured by appropriately selecting the elements of the LC resonator. By adopting such a configuration, it is possible to cope with a high frequency and stabilize the frequency.

  However, in the case of only the basic components, the resonance frequency band of the LC resonator is fixed by the characteristics of the piezoelectric resonator 5, and at higher frequencies, oscillation occurs in a narrower frequency band and the start-up conditions are very strict. It is difficult to adjust.

[Characteristics of the first piezoelectric oscillator]
Therefore, in the first piezoelectric oscillator, a varicap diode 7 whose capacity is variable is connected in parallel to the LC resonator composed of the coil (L1) 2 and the capacitor (C1) 3 in addition to the basic components described above. Furthermore, a time constant circuit comprising a resistor (R4) 8 and a capacitor (C2) 9 is provided between the varicap diode 7 and the power supply voltage (Vcc).
That is, the power supply voltage (Vcc) is applied to the varicap diode 7 via the time constant circuit.

In the time constant circuit, one end of the resistor (R4) 8 is connected to the power supply voltage (Vcc), the other end is connected to one end of the capacitor (C2) 9, and the other end of the capacitor (C2) 9 is grounded. . The resistor (R4) 8 and the capacitor (C2) 9 correspond to the resistor and the fifth capacitor in the claims, respectively.
The cathode side of the varicap diode 7 and one end of the LC resonator are connected to a point between the other end of the resistor (R4) 8 and one end of the capacitor (C2) 9.

The time constant circuit gradually increases the voltage applied to the varicap diode 7 when the power is turned on in accordance with the time constant, and accordingly changes the capacitance of the capacitor portion of the LC resonator within a certain range. Is. The characteristics of the time constant circuit are determined by the element constants of the resistor (R4) 8 and the capacitor (C2) 9, and are appropriately selected so as to obtain a desired oscillator output.
As a result, the resonance characteristics of the LC resonator can be changed within a certain range, and when the capacitance according to the characteristics of the piezoelectric resonator 5 is reached, oscillation occurs at a specific frequency.

In the configuration example of FIG. 1, since the capacitor (C1) 3 is connected in parallel with the varicap diode 7, the voltage change applied to the varicap diode 7 can be increased, and a variable capacity can be widened. It is something that can be done.
After the power is turned on, the capacitance is changed by changing the voltage applied to the varicap diode 7, and the frequency that is resonated by the coil (L 1) 2, the capacitor (C 1) 3, and the varicap diode 7 is When the resonance frequency is reached, the oscillation state is entered.
That is, in the first piezoelectric oscillator, the starting condition of oscillation that becomes very severe at a high frequency is relaxed, adjustment is facilitated, and oscillation can be stably performed in a wider frequency range.

  In particular, in the first piezoelectric oscillator, since the variable range of the capacitance of the LC resonator is wide, even when the piezoelectric resonator 5 having different characteristics is mounted, the capacitance of the LC resonator is increased by the varicap diode 7 and the time constant circuit. It is possible to adjust and start oscillation at different frequencies, provide stable oscillation in a wider frequency range, and can constitute an oscillator using various piezoelectric resonators 5; It is intended to improve versatility.

[Piezoelectric Oscillator of Second Embodiment: FIG. 2]
Next, a piezoelectric oscillator according to a second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a circuit diagram of a piezoelectric oscillator according to the second embodiment of the present invention.
As shown in FIG. 2, the piezoelectric oscillator (second piezoelectric oscillator) according to the second embodiment of the present invention includes a varicap diode 7 connected in series with a capacitor (C 1) 3 in an LC resonator. A time constant circuit similar to that of the first piezoelectric oscillator is connected to the cathode side of the cap diode.
The other components are the same as those of the first piezoelectric oscillator, and can achieve high frequency and frequency stabilization using the reflection characteristics of the reflection element.

  In the second piezoelectric oscillator, the capacitance of the LC resonator is determined by the series-connected capacitor (C1) 3 and the varicap diode 7, and the capacitance can be varied within a certain range, but the capacitance can be varied. The range is narrower than that of the first and second piezoelectric oscillators.

  Still, compared to the case where the varicap diode 7 and the time constant circuit are not provided, the oscillation starting condition can be relaxed, and in particular, the frequency of the LC resonator can be finely adjusted in a specific narrow frequency range. Adjustment according to the characteristics of the piezoelectric resonator 5 is facilitated, and a stable oscillation frequency can be output.

[Piezoelectric Oscillator of Third Embodiment: FIG. 3]
Next, a piezoelectric oscillator according to a third embodiment of the present invention will be described with reference to FIG. FIG. 3 is a circuit diagram of a piezoelectric oscillator according to the third embodiment of the present invention.
As shown in FIG. 3, the piezoelectric oscillator (third piezoelectric oscillator) according to the third embodiment of the present invention has substantially the same configuration as the second piezoelectric oscillator. In the LC resonator, the varicap diode 7 Further, a capacitor (C5) 13 is further connected to the cathode side, and a time constant circuit is connected to a point between the cathode of the varicap diode 7 and the capacitor (C5) 13.
The capacitor (C5) 13 corresponds to the fourth capacitor described in the claims.

  In the third piezoelectric oscillator, the capacitance variable range in the LC resonator can be designed more finely than in the second piezoelectric oscillator, and the oscillation starting condition is relaxed in the same manner as in the second piezoelectric oscillator. The frequency can be finely adjusted within a specific narrow frequency range, the adjustment according to the characteristics of the piezoelectric resonator 5 is facilitated, and a stable oscillation frequency can be output.

[Piezoelectric Oscillator of Fourth Embodiment: FIG. 4]
Next, a piezoelectric oscillator according to a fourth embodiment of the invention will be described with reference to FIG. FIG. 4 is a circuit diagram of a piezoelectric oscillator according to the fourth embodiment of the present invention.
As shown in FIG. 4, a piezoelectric oscillator according to a fourth embodiment of the present invention (fourth piezoelectric oscillator) is a varicap in parallel with an LC resonator composed of a coil (L1) 2 and a capacitor (C1) 3. A diode 7 is connected, a capacitor (C3) 11 is connected to the anode side of the varicap diode 7, and a capacitor (C4) 12 is connected to the cathode side.
The capacitor (C3) 11 and the capacitor (C4) 12 respectively correspond to the second capacitor and the third capacitor described in the claims.

A time constant circuit similar to the third piezoelectric oscillator is connected to a point between the cathode side of the varicap diode 7 and the capacitor (C4) 12, and the power supply voltage is connected to the varicap diode 7 via the time constant circuit. Is applied.
As a result, the voltage applied to the varicap diode 7 increases to the outside, and oscillation can be started when the capacitance of the LC resonator reaches the capacitance according to the characteristics of the piezoelectric resonator 5, and the oscillation frequency of the LC resonator. Can be varied within a specific range.
Since the other basic components of the fourth piezoelectric oscillator are the same as those of the first to third piezoelectric oscillators described above, description thereof is omitted.

In the fourth piezoelectric oscillator, similarly to the first to third piezoelectric oscillators, the reflection characteristics of the reflecting element are used to increase the frequency and stabilize the frequency, and the capacitance of the LC resonator can be varied within a specific range. The start-up conditions can be relaxed, the LC resonator can oscillate in a wider frequency range, adjustment according to the characteristics of the piezoelectric resonator 5 is facilitated, and stable oscillation even when the piezoelectric resonator 5 having different characteristics is mounted The frequency can be output.
Note that the capacitance variable range of the LC resonator in the fourth piezoelectric oscillator is two capacitors (C3) 11 and two capacitors (C4) 12 so as to be in series with the varicap diode 7 in parallel with the coil (L1) 2. Since they are connected, the capacitance value is the combined capacitance of the three, and the capacitance variable range is narrower than that of the first piezoelectric oscillator.

[Effect of the embodiment]
According to the piezoelectric oscillator according to the first embodiment of the present invention, the LC resonance circuit in which the coil (L1) 2 and the capacitor (C1) 3 are connected in parallel is connected to the gate of the transistor 1, and the output terminal 10 is connected to the drain. The power supply voltage (Vcc) is applied to the output terminal 10 side, the piezoelectric resonator 5 as a reflective element is connected to the source, and the varicap diode 7 is connected in parallel to the LC resonator. Since the power supply voltage (Vcc) is applied to the cathode side of the diode 7 through a time constant circuit composed of a resistor (R4) 8 and a capacitor (C2) 9, the frequency is increased using the reflection characteristics of the reflection element. In addition to stabilizing the frequency, the capacitance of the LC resonator can be varied over a wide range, and the voltage applied to the varicap diode 7 is gradually increased to achieve piezoelectric resonance. The start conditions according to the characteristics of the resonator 5 can be relaxed to obtain stable oscillation, and the versatility can be improved by being compatible with various piezoelectric resonators 5.

  Further, according to the piezoelectric oscillator according to the second embodiment of the present invention, the varicap diode is connected in series with the capacitor (C1) 3 of the LC resonator in which the coil (L1) 2 and the capacitor (C1) 3 are connected in parallel. 7 is connected, and a time constant circuit is connected to the cathode side of the varicap diode 7, the capacitance of the LC resonator is varied within a specific range, and the voltage applied to the varicap diode 7 is gradually increased. As a result, the starting condition according to the characteristics of the piezoelectric resonator 5 is relaxed, and stable oscillation can be obtained.

  The present invention is suitable for a piezoelectric oscillator that can increase the frequency and stabilize the frequency using the reflection characteristics of the reflection element and can oscillate stably according to the characteristics of the reflection element.

  1 ... transistor, 2 ... coil (L1), 3 ... capacitor (C1), 4 ... resistance (R2), 5 ... piezoelectric resonator, 6 ... resistance (R3), 7 ... varicap diode, 8 ... resistor (R4), 9 ... capacitor (C2), 10 ... output terminal

Claims (5)

A piezoelectric oscillator including a transistor,
An LC resonator having a parallel-connected coil and a first capacitor is connected to the gate of the transistor,
A power supply voltage is applied to the drain of the transistor,
A piezoelectric resonator as a reflective element is connected to the source of the transistor,
An output terminal is provided on the drain side of the transistor;
A varicap diode is connected in parallel to the LC resonator,
A piezoelectric oscillator, wherein a cathode side of the varicap diode is connected to a gate of the transistor, and a power supply voltage is applied to the cathode side via a time constant circuit. A second capacitor is connected to the anode side of the varicap diode, and a third capacitor is connected to the cathode side of the varicap diode;
2. The piezoelectric oscillator according to claim 1, wherein a time constant circuit is connected to a point between the cathode side of the varicap diode and the third capacitor. A piezoelectric oscillator including a transistor,
An LC resonator having a parallel-connected coil and a first capacitor is connected to the gate of the transistor,
A power supply voltage is applied to the drain of the transistor,
A piezoelectric resonator as a reflective element is connected to the source of the transistor,
An output terminal is provided on the drain side of the transistor;
A varicap diode is connected in series with the first capacitor of the LC resonator;
A piezoelectric oscillator, wherein a cathode side of the varicap diode is connected to a gate of the transistor, and a power supply voltage is applied to the cathode side via a time constant circuit. A fourth capacitor is connected to the cathode side of the varicap diode,
4. The piezoelectric oscillator according to claim 3, wherein a time constant circuit is connected to a point between the cathode side of the varicap diode and the fourth capacitor. A time constant circuit, a resistor having one end connected to the cathode side of the varicap diode and the other end connected to the power supply voltage;
5. The piezoelectric oscillator according to claim 1, further comprising a fifth capacitor having one end connected to a point between the resistor and the cathode side of the varicap diode and the other end grounded. .

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