JP5115178B2 - Oscillator - Google Patents

Description

The present invention relates to an oscillator, and more particularly, to a circuit technology that enables a variable range of an oscillation frequency to be adjusted over a wide range by a control voltage.

Conventionally, an oscillator using an inverter amplifier circuit has been proposed, which contributes to downsizing of the device.
This oscillator is generally configured to feedback-amplify the oscillation of a piezoelectric vibrator. But,
The oscillation frequency of the piezoelectric vibrator is determined by the capacitance of the capacitive element in the oscillation loop portion and is fixed. Therefore, as a method of making the output oscillation frequency variable, V as shown in FIG.
There is a CO (Voltage Controlled Oscillator).

FIG. 10 is a circuit diagram of a conventional inverter oscillator disclosed in Patent Document 1. In FIG. This inverter oscillator basically includes an inverter amplifier circuit 31 including an inverter 34 and a feedback resistor 35, an oscillator 32, and a voltage control unit 33.
A DC blocking capacitive element 38 is connected in series to the input side of the inverter 34, and a voltage variable capacitive element 39 is connected between one terminal A on the capacitive element 38 side of the series circuit and the grounding circuit. In addition, one terminal (midpoint) A and a terminal B for applying a control voltage are connected via a resistor 40. Further, an oscillator 3 is connected to a series circuit of the inverter circuit 34 and the capacitive element 38.
2 are connected in parallel, and a capacitor element 37 is connected between the output side of the inverter circuit 34 and the grounding circuit.
In such a configuration, a closed circuit including the oscillator 32, the capacitive element 37, and the voltage-controlled variable capacitive element 39 serves as an oscillation loop unit that determines an oscillation frequency. The oscillation frequency can be adjusted by applying a control voltage from the terminal B and making the capacitance of the voltage variable capacitance element 39 variable.

Further, Patent Document 2 discloses a voltage controlled oscillator having variable capacitance units at the input and output of an oscillation amplifier circuit.
Japanese Patent Laid-Open No. 7-273547 JP-A-3-68203

However, the prior arts disclosed in Patent Documents 1 and 2 both have a configuration in which the variable capacitance element 39 is provided only in the oscillation loop section.
In such a configuration, in order to set the frequency change amount with respect to the capacitance change amount of the variable capacitance element 39 as large as possible, it is necessary to configure the capacitance variable range of the variable capacitance element 39 wide.
However, there is a limit to the expansion of the capacitance change range of the variable capacitance element 39.
In particular, when an oscillation circuit portion other than the piezoelectric vibrator is integrated into an integrated circuit (IC chip), it is necessary to review the IC chip manufacturing process in detail in order to optimize the capacitance change range of the variable capacitance element 39. It is not easy in practice because of development time and cost.
Further, even if the IC chip manufacturing process is reviewed and optimized design is performed in the simulation, the actual device is strongly influenced by the parasitic capacitance generated in parallel with the variable capacitance element 39, and the desired frequency change. There was a problem that the control function of quantity and frequency could not be obtained.
The present invention has been made in view of the above problems, and an object of the present invention is to provide an inverter oscillator that can easily control the variable amount of the oscillation frequency and expand the variable range of the oscillation frequency.

An application example of the present invention includes a vibrator and a plurality of capacitive elements that are connected in series with each other, and the vibrator and the plurality of capacitive elements are connected in series and are connected in series in the plurality of capacitive elements. An oscillating loop unit whose midpoint of connection is connected to the first constant potential circuit;
Outside the oscillation loop unit, the semiconductor device includes a variable capacitance element and a semiconductor integrated amplification circuit to which a power source having the first constant potential as a reference potential is connected, and the amplification circuit and the variable capacitance element are connected in series. A series circuit connected to each other, and the circuit between two connection midpoints excluding the connection midpoint in the oscillation loop section and the series circuit are connected in parallel.

The present invention connects a variable capacitance element in series to an amplifier circuit, and by connecting an oscillation loop unit in parallel to this series circuit, it is possible to make the parasitic capacitance work as a bypass capacitor of the variable capacitance element, and to change the frequency greatly. be able to.
The variable capacitance element is a voltage control type variable capacitance element, and an AC blocking resistor is connected between one voltage input terminal of the variable capacitance element and one connection point of the closed circuit. It is the structure.

In the present invention, a variable capacitance element is connected in series to an amplifier circuit, and an oscillation loop unit is connected in parallel to this series circuit, so that the parasitic capacitance is actively used, and the frequency is greatly increased with a small change in control voltage. Can be changed.
Further, the capacitor circuit includes a capacitor element made of a variable capacitor element.

The application example of the present invention is characterized in that, in addition to the above application example, the variable capacitance element is a MOS type variable capacitance element.
An application example of the present invention is characterized in that, in addition to the application example described above, the capacitive element is another variable capacitive element.
As a result , the variable capacitance element is connected in series to the amplifier circuit, and the oscillation loop unit is connected in parallel to the series circuit, thereby allowing the parasitic capacitance to function as a bypass capacitor of the variable capacitance element, and greatly changing the frequency. it can.
In addition to the above application example, the application example of the present invention is that the first constant potential circuit is a grounding circuit, and the amplifier circuit is a single power supply type inverter amplifier circuit having a ground terminal. Features.

As a result , the variable capacitance element is connected in series to the amplifier circuit, and the oscillation loop unit is connected in parallel to the series circuit, thereby allowing the parasitic capacitance to function as a bypass capacitor of the variable capacitance element, and greatly changing the frequency. it can.
In addition to the above application example, the application example of the present invention is characterized in that the amplifier circuit is an NPN transistor, and the emitter of the transistor is connected to a grounding circuit.

As a result , the variable capacitance element is connected in series to the amplifier circuit, and the oscillation loop unit is connected in parallel to the series circuit, thereby allowing the parasitic capacitance to function as a bypass capacitor of the variable capacitance element, and greatly changing the frequency. An oscillator having excellent noise characteristics can be realized.

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the components, types, combinations, shapes, relative arrangements, and the like described in this embodiment are merely illustrative examples and not intended to limit the scope of the present invention only unless otherwise specified. .

FIG. 1 is a circuit configuration diagram of an oscillator according to a first embodiment of the present invention. An oscillator 50 according to the present invention includes an amplifier circuit composed of a semiconductor element having a ground potential, which is a first constant potential, as a reference potential of a power supply voltage, a crystal resonator (piezoelectric resonator) X, and a crystal resonator X. A capacitance circuit constituting the circuit and a voltage-controlled variable capacitance element (varactor) are provided.
Further, the amplifier circuit is, for example, a single power supply type, and includes an inverter circuit 5 having a ground terminal for connection to a ground circuit (first constant potential circuit) in addition to a power supply terminal and an input / output terminal; This is an inverter amplifier circuit composed of a feedback resistor Rf.
The inverter amplifier circuit and the varactor 3 constitute a first series circuit via a direct current blocking capacitive element C3.
In this configuration, the first series circuit is connected to the crystal unit X in parallel.
The capacitive circuit is a series circuit in which one terminal of the capacitive element C1 and the capacitive element C2 is connected to a grounding circuit (first constant potential circuit).
It has a closed circuit in which a capacitor circuit and a crystal unit X are connected in parallel.
Further, the voltage input terminal 1 and the voltage input terminal (reference voltage input terminal) 2 are terminals to which a control voltage for controlling the capacitance value of the varactor 3 is applied.
The voltage input terminal 1 is connected to one terminal of the varactor 3 via an AC blocking resistor R1,
The reference voltage input terminal 2 is connected to the other terminal of the varactor 3 through an AC blocking resistor R2.
The oscillator 50 shown in FIG. 1A is connected to the variable capacitance element 3 on the input terminal side of the inverter circuit 5.
1B is connected to the cathode of the variable capacitance element 3 on the input terminal side of the inverter circuit 5.
In such a circuit, a closed circuit including a crystal resonator X, a capacitive element C1, a capacitive element C2, and a grounding circuit is used as an oscillation loop section (resonance circuit section) 4 that mainly affects the oscillation state of the oscillation circuit. It is.
In this embodiment, the circuit configuration uses a bipolar variable capacitance diode as the voltage variable capacitance element. However, a MOS variable capacitance element may be used as another element.
The MOS type variable capacitance element has a characteristic that the capacitance change amount with respect to the voltage change is larger than that of the bipolar type variable capacitance diode.
Therefore, the configuration of the oscillation circuit according to the present invention is effective for realizing an oscillator having a wide frequency variable range by effectively utilizing such excellent characteristics of the MOS type variable capacitance element.

In the oscillator 50 having such a configuration, since a parasitic capacitance exists between the input terminal of the inverter circuit 5 and the grounding circuit, the anode of the variable capacitance element 3 is grounded via the parasitic capacitance and the capacitance element C3. It has the structure connected to the circuit for this.
That is, this embodiment has a configuration in which a variable capacitance element is inserted and connected between at least one of the input terminal or the output terminal of the amplifier circuit and the circuit wiring (other than the grounding circuit) constituting the oscillation loop unit. It is a feature.
In such a configuration, a bypass-dedicated capacitive element is not prepared between the terminal of the varactor 3 on the connection side to the amplifier circuit and the grounding circuit, but an amplifier circuit as a semiconductor element (semiconductor component). The parasitic capacitance (for example: parasitic capacitance generated between the input terminal of the inverter circuit or transistor and the ground), which has been troublesome as a factor that hinders the increase in the frequency change amount, is used for the varactor 3 and the ground. As compared with the configuration in which a series circuit composed of a varactor and a fixed capacitance element is simply connected in parallel to the capacitance element C1, this circuit is actively utilized as a bypass capacitance element for AC connection. In addition to the advantage that the frequency variable amount can be easily controlled, it is also advantageous for downsizing the oscillator.
Further, the present invention may be applied to an oscillator in which a circuit constituting an oscillator other than the crystal unit X is configured by a single IC chip. In this case, since a large amount of stray capacitance is generated in the IC chip, the varactor 3 is provided. Since the stray capacitance with a larger value can be connected to the grounding circuit, the varactor 3 can function more effectively.

FIG. 2 is a circuit configuration diagram of an inverter oscillator according to the second embodiment of the present invention. The same components as those in the embodiment of FIG. 1 will be described with the same reference numerals as those in FIG. This inverter oscillator omits the direct current blocking capacitive element C3 of FIG. 1 and connects the capacitive circuit of the oscillation loop section 4 in parallel to a series circuit in which one terminal of the varactor 3 is connected to the input side of the inverter circuit 5. The bias voltage on the input side or output side of the inverter circuit 5 is used as a reference voltage to be applied to the varactor 3.
That is, in the present embodiment shown in FIG. 2A, the direct current blocking capacitance element C3 is omitted from the circuit diagram shown in FIG. This is connected to the input side of the amplifier circuit. Therefore, the reference voltage of the varactor 3 uses the bias voltage generated by the feedback resistor Rf fed back to the input of the inverter circuit 5.
A circuit for applying the capacitor C3 and the reference voltage is not necessary, and the circuit configuration can be further simplified.
The inverter oscillator 51 </ b> A in FIG. 2B is obtained by inverting the polarity of the varactor 3.

FIG. 3 is a circuit configuration diagram of an inverter oscillator according to the third embodiment of the present invention. The same components as those in the embodiment of FIG. 1 will be described with the same reference numerals as those in FIG. The oscillator 52 includes an amplifier circuit having a feedback resistor Rf and an inverter circuit 5, a crystal resonator X connected between input and output terminals of the inverter circuit 5, and an oscillation loop section 4 including the crystal resonator X. Inverter oscillator.
A DC blocking capacitive element C3 connected to the output side of the inverter circuit 5 and a varactor 3 connected in series to the DC blocking capacitive element C3 are provided.
In addition, a series circuit between the input side of the inverter circuit 5 and one terminal of the varactor 3 is connected in parallel to the capacitor circuit constituting the oscillation loop unit 4.
The oscillation circuit 52 having such a configuration changes the oscillation frequency of the oscillator 52 by changing the potential difference between the terminals of the varactor 3 and changing the capacitance of the varactor 3.
In the embodiment of FIG. 3A, a DC element capacitor C3 is connected to the output side of the inverter circuit 5 having the feedback resistor Rf so as not to affect the output bias voltage of the inverter circuit 5. The anode of the varactor 3 is connected in series to the other end of the capacitive element C3, and the cathode is connected in parallel to the oscillation loop section 4.
A connection point between the capacitive element C3 and the output terminal of the amplifier circuit is connected to the ground via a parasitic capacitance between the output terminal of the inverter circuit 5 that is a semiconductor component and the ground. For that reason,
By changing the potential difference between the terminals of the varactor 3 to vary the capacitance of the varactor 3, the parallel capacitance of the capacitive element C2 changes, so that the oscillation frequency of the oscillator 50 can be varied.
With this configuration, by applying a potential difference to both ends of the varactor 3, the capacitance is changed to make the oscillation frequency variable. As a result, the parasitic capacitance can be used as a bypass capacitor of the variable capacitance element, and the frequency can be changed greatly with a small change in control voltage.
The inverter oscillator 52A in FIG. 3B is obtained by inverting the polarity of the varactor 3.

FIG. 4 is a circuit configuration diagram of an inverter oscillator according to the fourth embodiment of the present invention. The same components as those in the embodiment of FIG. 1 will be described with the same reference numerals as those in FIG.
The inverter oscillator 53 omits the DC blocking capacitive element C3 from the circuit shown in FIG. 3, connects one terminal of the varactor 3 and the output side of the inverter circuit 5, The other terminal of the varactor 3 is connected in parallel to the capacitor circuit that constitutes the oscillation loop unit 4,
The bias voltage on the output side of the inverter circuit 5 is used as the reference voltage for the varactor 3.
Therefore, the reference voltage of the varactor 3 uses a bias voltage generated from the output of the inverter circuit 5. As a result, the capacitor C3 and a circuit for applying the reference voltage are not necessary, and the circuit configuration can be further simplified.
The inverter oscillator 53A in FIG. 4B is obtained by inverting the polarity of the varactor 3.

FIG. 5 is a circuit configuration diagram of an inverter oscillator according to the fifth embodiment of the present invention. The same components as those in the embodiment of FIG. 1 will be described with the same reference numerals as those in FIG. The inverter oscillator 54 includes an amplifier circuit having a feedback resistor Rf and an inverter circuit 5, a crystal resonator X connected between input and output terminals of the inverter circuit 5, and an oscillation loop section 4 including the crystal resonator X. An inverter oscillator provided.
Then, one terminal of the DC blocking capacitive element C3 is connected to the input terminal side of the inverter circuit 5, the DC blocking capacitive element C4 is connected to the output terminal side, and the other terminal of each DC blocking capacitive element C3. And one terminal of the varactor 3 is connected.
In addition, the other terminal of the capacitive element C4, a series circuit connected to the varactor 6, and
The series circuit has a configuration in which the series circuit is connected in parallel to a capacitor circuit that constitutes the oscillation loop unit 4.
Such an oscillator 53 applies a potential difference to both ends of each varactor 3, 6 to provide each varactor 3, 6.
The oscillation frequency of the inverter oscillator 54 is varied by making the capacitance of the inverter oscillator 54 variable.
Although not shown, the polarities of the varactors 3 and 6 may be reversed. Further, the DC blocking capacitance elements C3 and C4, the terminal 2 and the terminal 7 are omitted, the bias voltage on the input / output side of the amplifier circuit is used as a reference voltage, and a control voltage which is a variable voltage is input to the terminals 1 and 8 It does not matter if it is configured.
That is, in the present embodiment, a plurality of varactors 3 and 6 are connected in series, and the oscillation loop section 4
Are connected in parallel, the frequency variable range is wide and complex control can be performed.

FIG. 6 is a circuit configuration diagram of an inverter oscillator according to the sixth embodiment of the present invention.
The same components will be described with the same reference numerals as in FIG. In this oscillator 55, at least one capacitive element (C1 in this embodiment) in the oscillation loop section 4 of the embodiment in FIG. In the present embodiment, the configuration of FIG. 2 is described as an example, but the present invention can be applied to the oscillators of all the embodiments.
In other words, in the present embodiment, the capacitive element C1 in the oscillation loop unit 4 is replaced with the varactor 9 in the circuit diagram shown in FIG. Thereby, the variable range of the oscillation frequency can be further expanded as compared with the case where the frequency is controlled only by the varactor 3. It is effective to replace the position where the varactor 9 is inserted with a capacitive element at the position where the control voltage is applied.
In addition to the advantage of easily controlling the variable amount of frequency as compared with the configuration in which another varactor is simply connected in parallel to the varactor 9 through a fixed capacitor without using the varactor 3, this configuration is possible. This is also advantageous for downsizing the oscillator.
1 to 6, it is also possible to insert a DC blocking capacitive element between the varactor 3 and the oscillation loop section (C1 or C2).
In the above description, the case where the oscillator circuit is applied to an inverter type oscillator has been described. However, the present invention is not limited to this, and the present invention can be applied to an oscillator having another configuration such as a Colpitts type. is not.

FIG. 7 is a circuit configuration diagram of an inverter oscillator according to the seventh embodiment of the present invention. The same components will be described with the same reference numerals as in FIG. The oscillator 56 includes varactors D2 and D3.
This is a temperature compensated oscillator configured to be able to apply a temperature compensated voltage to.
That is, the varactor D2 and a terminal for applying a temperature compensation voltage are connected via a resistor R3, and the varactor D3 and a terminal for applying a temperature compensation voltage are connected via a resistor R4. As the temperature compensation voltage, for example, a control voltage having a voltage change characteristic exhibiting a linear function with respect to temperature is applied. Further, for example, by applying a control voltage having a voltage characteristic exhibiting a linear function to the varactor 3, the frequency temperature compensation capability of the oscillator can be increased. Thereby, the cut angle of the crystal oscillator X capable of temperature compensation can be widened.
That is, with the above-described oscillation circuit 56, it is possible to compensate for the temperature without difficulty even when the variation of the frequency temperature characteristic among the crystal resonators X is large.
When the negative resistance of the oscillation circuit is small and difficult to oscillate at low temperatures, it is preferable to apply a control voltage that greatly changes the capacitance value of the varactor 3 as the temperature decreases. In such a configuration, since the impedance between the input terminal of the amplifier circuit and the oscillation loop unit is controlled at a low temperature, oscillation is likely to occur.
As the varactor, a MOS type varactor can be used. In this case, for example, in order to connect the MOS varactor instead of the varactor 3, the gate of the MOS varactor and the resistor R1 may be connected, and the back gate of the MOS varactor and the resistor R2 may be connected.
Further, the amplifier circuit is not limited to an inverter amplifier circuit using CMOS, and a configuration in which an NPN bipolar transistor Tr and a current source 11 are combined as shown in FIG.
That is, the oscillation circuit 57 shown in FIG. 8 includes an amplifier circuit having a transistor Tr and a self-bias resistor R1.
The transistor Tr has a collector connected to the current source 11, and is connected to one terminal of a DC blocking capacitor C5, an emitter connected to a grounding circuit, and a base connected to the DC blocking capacitor C6. And connected to the anode of the varactor D1.
In addition to such a configuration, the oscillation circuit 57 has the cathode of the varactor D1 connected to the grounding circuit via the varactor D2, and the other terminal of the capacitive element C5 connected to the grounding circuit via the varactor D3. It has a configuration.
Further, a terminal for applying a control voltage to the connection point between the varactor D1 and the varactor D2 is connected via a resistor R3, and a terminal for applying a control voltage to the connection point between the varactor D3 and the capacitive element C5. A configuration in which the crystal resonator X is connected between the two connection points is connected through the resistor R4, and the anode of the varactor D1 is connected to the reference voltage input terminal 2 through the resistor R2. Have.
Such a transistor configuration has better noise characteristics.
Therefore, according to the present invention, the frequency change amount by the variable capacitance element and the frequency change amount per unit voltage change (frequency sensitivity characteristic) are increased to cancel the tendency to deteriorate the noise characteristic, thereby realizing an oscillator having excellent noise characteristic. Therefore, it is particularly effective for an oscillator having excellent frequency sensitivity characteristics using a MOS type variable capacitance element.

FIG. 9 is a schematic diagram for explaining variations of the oscillation loop unit shown in FIGS.
For example, 1) Both CC and CD are set to 0Ω, CA and CB are fixed-value capacitive elements, and Z is set to 0Ω, thereby forming the oscillation loop unit shown in FIGS.
In the configuration shown in FIG. 6, both CC and CD are 0Ω, CA is a variable capacitor, CB is a fixed capacitor, and Z is 0Ω.
Furthermore, with the configuration of FIG. 7, both CC and CD are fixed capacitance elements, CA and CB are variable capacitance elements, and Z is 0Ω.
In the configuration of FIG. 8, both CA and CB are variable capacitance elements, CC and CB are 0Ω, and Z is 0Ω.
It becomes.
In other words, the configuration of the oscillation loop unit may be any one of CA, CB, CC, and CD, a variable capacitor, a fixed capacitor, or a combination thereof.

It is a circuit block diagram of the inverter oscillator which concerns on the 1st Embodiment of this invention. It is a circuit block diagram of the inverter oscillator which concerns on the 2nd Embodiment of this invention. It is a circuit block diagram of the inverter oscillator which concerns on the 3rd Embodiment of this invention. It is a circuit block diagram of the inverter oscillator which concerns on the 4th Embodiment of this invention. It is a circuit block diagram of the inverter oscillator which concerns on the 5th Embodiment of this invention. It is a circuit block diagram of the inverter oscillator which concerns on the 6th Embodiment of this invention. It is a circuit block diagram of the inverter oscillator which concerns on the 7th Embodiment of this invention. It is a figure which shows the modification Example of FIG. It is a schematic diagram for demonstrating the variation of the oscillation loop part shown to FIGS. FIG. 10 is a circuit diagram of a conventional inverter oscillation circuit disclosed in Patent Document 1.

Explanation of symbols

1 control voltage input terminal, 2 reference voltage input terminal, 3 varactor, 4 oscillation loop section, 5 inverter circuit, R1, R2 resistance, Rf feedback resistance, C1, C2, C3, C4,
C5, C6 capacitive element, X crystal resonator, 50-55 inverter oscillator

Claims (6)

The vibrator includes a plurality of capacitive elements that are connected in series with each other, and the vibrator and the plurality of capacitive elements are connected in series, and the connection midpoint of the plurality of capacitive elements is a first connection point An oscillation loop connected to a constant potential circuit;
Outside the oscillation loop unit, the semiconductor device includes a variable capacitance element and a semiconductor integrated amplification circuit to which a power source having the first constant potential as a reference potential is connected, and the amplification circuit and the variable capacitance element are connected in series. A connected series circuit;
With
Oscillator, characterized in that the circuit before Symbol series circuit between the two connection midpoint excluding the connection point in the oscillation loop portion are connected in parallel. The variable capacitance element is a variable capacitance element of the voltage controlled, the variable one of the voltage input terminal of the capacitor and between one connection point of the oscillation loop part is connected to the resistor for an AC blocking oscillator of claim 1, characterized in that there.   The oscillator according to claim 2, wherein the variable capacitance element is a MOS type variable capacitance element. Oscillator according to any one of claims 1 to 3, wherein the capacitive element is another variable capacitance element. Wherein a first circuit of the circuit ground for the constant potential, to any one of claims 1 to 4 wherein the amplifier circuit is characterized in that it is a single supply type inverter amplifier circuit having a ground terminal The oscillator described. The amplifier circuit is an NPN type transistor, oscillator according to any one of claims 1 to 5, characterized in that the emitter of the transistor is connected to a circuit ground.

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