JP5129092B2 - Voltage controlled oscillator - Google Patents

Description

  The present invention relates to a voltage controlled oscillator that suppresses a change in negative resistance caused by a change in control voltage.

Conventionally, as an oscillator using a piezoelectric vibrator (vibrator) such as a crystal vibrator, there is a voltage controlled oscillator 1 having a configuration shown in FIG. FIG. 7 is a diagram showing a configuration of a conventional voltage controlled oscillator 1.
As shown in FIG. 7, the voltage controlled oscillator 1 includes an amplifier circuit A, two variable capacitance elements C _L, and a resistance element R ₁ .
The amplification circuit A is formed using an inverting amplification circuit, and each variable capacitance element C _L connected in parallel to the vibrator X is connected to the input side and the output side of the amplification circuit A, respectively. The capacitance value changes depending on the control voltage V _cont to be applied.

The resistance element R ₁ is connected between the vibrator X and the output side of the amplifier circuit A.
The resonator X is a crystal resonator and has an equivalent circuit shown in FIG. FIG. 8 is a diagram illustrating a configuration of an equivalent circuit of the vibrator X.
In such a voltage controlled oscillator 1, in order to control the oscillation frequency at which the vibrator X oscillates, the control voltage V _cont applied to each variable capacitance element C _L is changed, whereby each variable capacitance element C _L The oscillation frequency is changed by changing the capacitance value.
The change in the oscillation frequency is expressed by the following equation (1), where the oscillation frequency is “F”.

  In addition, said Formula (1) presupposes that the following formula | equation (2) is satisfied.

In the voltage controlled oscillator 1 as described above, as an oscillation start condition, the equivalent resistance of the vibrator X is “R”, and the negative resistance of the circuit forming the voltage controlled oscillator 1 (hereinafter referred to as “negative resistance”) is described. When “−R” is set to “−R”, the absolute value of the negative resistance −R needs to be larger than the equivalent resistance R (| −R |> R).
The negative resistance -R is represented by the following formula (3), where the gain of the amplifier circuit A is “A”.

  In addition, said Formula (3) presupposes that the following formula | equation (4) is satisfied.

Thus, when changing the capacitance value of each variable capacitance element C _L in order to vary the oscillation frequency, negative resistance changes.
The relationship between the capacitance value of the variable capacitance element C _L and the resistance value of the resistance element R ₁ and the negative resistance is expressed by the following equation (5).

  In addition, said Formula (5) presupposes that the following formula | equation (6) is satisfied.

As shown in the above equation (5), as the capacitance value of the variable capacitance element C _L increases, the absolute value of the negative resistance decreases. Similarly, etc. When selecting a high resistance value components as the resistance element R _1, as the resistance value of the resistance element R ₁ increases, the absolute value of the negative resistance decreases.
On the other hand, as the capacitance of the variable capacitor C _L is decreased, the absolute value of the negative resistance is increased. Similarly, etc. When selecting a low resistance component as the resistance element R _1, as the resistance value of the resistance element R ₁ is decreased, the absolute value of the negative resistance is increased.
In general, the absolute value of the negative resistance is often set to at least five times the equivalent resistance of the vibrator X (| −R | ≧ 5R) in order to enable stable oscillation.

However, if the absolute value of the negative resistance is set in a state where the capacitance value of the variable capacitance element C _L is large and the negative resistance is the minimum value, the capacitance of the variable capacitance element C _L is changed from the state where the negative resistance is the minimum value. When the value decreases, the absolute value of the negative resistance becomes excessive.
If the absolute value of the negative resistance is excessive, there may be a problem that abnormal oscillation occurs, such as oscillation at the sub-resonance point. On the other hand, if the absolute value of the negative resistance is too small, there may be a problem that oscillation does not occur and a problem that oscillation stops.

Therefore, the variable range in which the capacitance value of the variable capacitance element C _L can be changed is limited, and there is a possibility that the relationship between stable oscillation and the frequency variable range becomes a trade-off relationship. is there.
For this problem, for example, inventions described in Patent Documents 1 to 3 have been proposed.
In the invention described in Patent Document 1, an amplifier and an oscillation amplifier including two divided capacitors are connected in series to a vibrator, and at least one of the two divided capacitors included in the oscillation amplifier is used as a variable capacitor. (Variable capacitance diode). As a result, the negative resistance is changed together with the control voltage, and the absolute value of the negative resistance is always set to a value larger than the effective resistance of the vibrator to prevent the oscillation from stopping.

In the invention described in Patent Document 2, a resistance element and a capacitor element connected in series are inserted in parallel into a variable capacitor element connected in series with a vibrator. Thereby, the oscillation phase condition of the vibrator is changed, and a frequency variable range larger than the conventional one is obtained.
The invention described in Patent Document 3 includes a detection circuit that detects the oscillation operation of the vibrator, and reduces the negative resistance when detecting the oscillation start in which the oscillation operation of the vibrator is in the initial state. As a result, the negative resistance necessary for maintaining good oscillation startability is obtained, and the variation width of the oscillation frequency is increased.
JP 10-56330 A JP 2002-165144 A JP 2002-344242 A

However, in the inventions described in Patent Documents 1 and 2, since the number of parts increases, there is a possibility that the problem of an increase in cost may occur. Further, since the control becomes complicated due to an increase in the number of parts, the constants of the circuit and each element are easily affected by variations and the like, and there is a possibility that it may be difficult to obtain stable oscillation.
Further, in the invention described in Patent Document 3, since the absolute value of the negative resistance before the start of oscillation is large, there may be a problem that abnormal oscillation occurs, such as oscillation at the secondary resonance point. Furthermore, there is a possibility that a problem that oscillation stops occurs by detecting the start of oscillation and lowering the negative resistance. In addition, after the oscillation starts, the detection circuit may decrease the negative resistance to stop the oscillation, and the detection circuit may increase the negative resistance, thereby repeating the oscillation start, oscillation, and stop states.
The present invention has been made paying attention to the above problems, and voltage control capable of obtaining stable oscillation and a wide frequency variable range in a state where the oscillation frequency is changed by changing the control voltage. It is an object to provide an oscillator.

In order to solve the above-mentioned problems, the invention described in claim 1 of the present invention is characterized in that a capacitor is connected by an amplifier circuit connected in parallel to the vibrator and a control voltage connected to the input side of the amplifier circuit and applied. At least one of a variable capacitance element whose value changes and a variable capacitance element which is connected to the output side of the amplifier circuit and whose capacitance value changes according to the applied control voltage; the vibrator; and the output side of the amplifier circuit; A variable resistance element connected between and having a resistance value changed by the applied control voltage, and a control voltage applying means for simultaneously applying the control voltage to the variable capacitance element and the variable resistance element ,
It said variable capacitance element and the variable resistance element, variation of the channel due to the application of the control voltage is one that is characterized that you formed in the same or substantially the same MOS transistor.

According to the present invention, the control voltage is applied simultaneously to the variable capacitance element whose capacitance value is changed by the applied control voltage and the variable resistance element whose resistance value is changed by the applied control voltage.
For this reason, it is possible to cancel out the change in the negative resistance due to the change in the capacitance value of the variable capacitance element and the change in the negative resistance due to the change in the resistance value of the variable resistance element caused by applying the control voltage. It becomes possible to suppress the change in the negative resistance caused by the change in the control voltage. This is because when the control voltage having the same value is applied to the variable capacitance element and the variable resistance element, the relationship between the variable capacitance element and the variable resistance element is the amount of change in the negative resistance due to the change in the capacitance value of the variable capacitance element. This corresponds to the case where the increase / decrease and the increase / decrease in the negative resistance change due to the change in the resistance value of the variable resistance element are opposite to each other.
Further, according to the present invention, the variable capacitance element and the variable resistance element are formed by MOS transistors having the same or substantially the same change in channel due to application of the control voltage.
For this reason, the change characteristic of the capacitance value of the variable capacitance element and the change characteristic of the resistance value of the variable resistance element are the same or substantially the same due to the application of the control voltage, and the control voltage applied to the variable capacitance element and the variable resistance element is shared. It becomes possible to do.

Next, the invention described in claim 2 is an amplification circuit connected in parallel to the vibrator, a variable capacitance element that is connected to the input side of the amplification circuit and whose capacitance value varies depending on the applied control voltage, and The control connected and applied between at least one of the variable capacitance elements connected to the output side of the amplifier circuit and having a capacitance value changed by the applied control voltage, and between the vibrator and the output side of the amplifier circuit. A variable resistance element whose resistance value changes according to voltage, and a control voltage applying means for simultaneously applying the control voltage to the variable capacitance element and the variable resistance element,
Said variable capacitance element and the variable resistance element and is characterized that you formed by sharing one of said MOS transistors.
According to the present invention, the control voltage is applied simultaneously to the variable capacitance element whose capacitance value is changed by the applied control voltage and the variable resistance element whose resistance value is changed by the applied control voltage.
For this reason, it is possible to cancel out the change in the negative resistance due to the change in the capacitance value of the variable capacitance element and the change in the negative resistance due to the change in the resistance value of the variable resistance element caused by applying the control voltage. It becomes possible to suppress the change in the negative resistance caused by the change in the control voltage. This is because when the control voltage having the same value is applied to the variable capacitance element and the variable resistance element, the relationship between the variable capacitance element and the variable resistance element is the amount of change in the negative resistance due to the change in the capacitance value of the variable capacitance element. This corresponds to the case where the increase / decrease and the increase / decrease in the negative resistance change due to the change in the resistance value of the variable resistance element are opposite to each other.
According to the present invention, the variable capacitance element and the variable resistance element are formed by sharing one MOS transistor.
For this reason, since one MOS transistor forms a variable capacitance element and a variable resistance element, there is no problem that matching between the variable capacitance element and the variable resistance element deteriorates. The operation can be stabilized.

Next, the invention described in claim 3 is the invention described in claim 1 or 2, wherein the variable voltage is applied between the control voltage applying means and the variable resistance element and applied to the variable resistance element. Control voltage conversion means for converting at least one of the level and gain of the resistance element side control voltage into a value different from the variable capacitance element side control voltage applied to the variable capacitance element;
The control voltage conversion means adjusts the level and gain of the variable resistance element side control voltage so as to cancel out the change in the negative resistance due to the change in the capacitance value and the change in the negative resistance due to the change in the resistance value. At least one of them is converted.
According to the present invention, the control voltage converting means cancels the change in the negative resistance due to the change in the capacitance value due to the application of the control voltage and the change in the negative resistance due to the change in the resistance value. At least one of the level and gain of the control voltage is converted to a value different from the variable capacitor side control voltage.
For this reason, the change in negative resistance due to the change in the capacitance value of the variable capacitance element and the change in negative resistance due to the change in the resistance value of the variable resistance element caused by applying the control voltage can be more efficiently performed. It becomes possible to cancel out, and it becomes possible to more efficiently suppress the change in the negative resistance caused by the change in the control voltage.

  According to the present invention, by applying a control voltage to the variable capacitance element and the variable resistance element at the same time, by applying the control voltage, the change in the negative resistance due to the change in the capacitance value of the variable capacitance element and the variable resistance element It is possible to cancel out the change in the negative resistance due to the change in the resistance value. For this reason, it is possible to suppress an increase in the number of components and to suppress a change in negative resistance caused by a change in control voltage, and to obtain a stable oscillation and a wide frequency variable range.

Embodiments of the present invention will be described below with reference to the drawings.
(First embodiment)
First, a first embodiment of the present invention (hereinafter referred to as “the present embodiment”) will be described with reference to the drawings.
(Constitution)
First, the configuration of the present embodiment will be described with reference to FIG. The same components as those of the above-described conventional voltage controlled oscillator will be described with the same reference numerals.
FIG. 1 is a diagram showing a configuration of a voltage controlled oscillator 1 of the present embodiment.
As shown in FIG. 1, the voltage controlled oscillator 1 includes an amplifier circuit A, two variable capacitance elements C _L , a variable resistance element R _V , a control voltage application unit 2, and a control voltage conversion unit 4. I have.
The amplifier circuit A is connected to the vibrator X in parallel.
The amplifier circuit A is formed using, for example, an inverting amplifier circuit. In the present embodiment, the case where the amplifier circuit A is formed using an inverting amplifier circuit will be described as an example.

The vibrator X is connected to the amplifier circuit A through two connection terminals 6.
The vibrator X is formed using a piezoelectric vibrator such as a quartz vibrator. In the present embodiment, the case where the vibrator X is formed using a crystal vibrator will be described as an example.
Each variable capacitance element C _L is connected to the input side and the output side of the amplifier circuit A, respectively.
Each variable capacitance element C _L is formed using, for example, a MOS transistor type capacitor. In the present embodiment, the case where each variable capacitance element _CL is formed using a MOS transistor type capacitor will be described as an example.

Further, the capacitance value of each variable capacitance element C _L changes according to the control voltage V _cont applied by the control voltage application means 2. More specifically, the control voltage capacitance value increases as V voltage value of _cont increases, the voltage value of the control voltage V _cont is the capacitance value decreases with decreasing.
The variable resistance element R _V is connected between the vibrator X and the output side of the amplifier circuit A.
The variable resistance element R _V is formed using, for example, a MOS transistor. In the present embodiment, a case where the variable resistance element R _V is formed using a MOS transistor will be described as an example.

Further, the resistance value of the variable resistance element R _V is changed by the control voltage V _cont applied by the control voltage applying means 2. Specifically, the resistance value decreases as the voltage value of the control voltage V _cont increases, and the resistance value increases as the voltage value of the control voltage V _cont decreases.
In the present embodiment, when selecting the respective variable capacitance elements C _L and the variable resistor element R _V, the relationship between each of the variable capacitance elements C _L and the variable resistor element R _V is, the control voltage V _cont of the same value When applied to each variable capacitance element C _L and variable resistance element R _V , the amount of change in negative resistance due to the change in capacitance value of each variable capacitance element C _L and the change in resistance value of variable resistance element R _V Select the parts that have the opposite relationship between the increase and decrease of the negative resistance change due to.

The control voltage applying means 2 applies the control voltage V _cont simultaneously to each variable capacitance element C _L and variable resistance element R _V.
The control voltage V _cont applied by the control voltage applying means 2 to each variable capacitance element C _L is a value necessary for controlling the oscillation frequency at which the vibrator X oscillates to a desired frequency. This value is a value that depends on the intrinsic properties to resonator X and the variable capacitance elements C _L, is set in advance. In FIG. 1 and the following description, the control voltage V _cont applied to each variable capacitance element C _L is described as “variable capacitance element side control voltage CV _cont ” and applied to the variable resistance element R _V. Distinguish from voltage V _cont .

The control voltage conversion unit 4 is connected between the control voltage application unit 2 and the variable resistance element R _V.
Further, the control voltage conversion means 4 is formed using, for example, a buffer. In the present embodiment, the case where the control voltage conversion means 4 is formed using a buffer will be described as an example.
Further, the control voltage converting means 4, at least one of the level and gain of the control voltage V _cont is applied to the variable resistive element R _V, into a value different from the variable capacitor the control voltage CV _cont. In FIG. 1 and the following description, the control voltage V _cont converted by the control voltage conversion means 4 and applied to the variable resistance element R _V is referred to as “variable resistance element side control voltage RV _cont ”, and is described above. It is distinguished from the variable capacitor side control voltage CV _cont .

Specifically, the control voltage conversion means 4 includes the amount of change in the negative resistance due to the change in the capacitance value of each variable capacitance element C _L to which the variable capacitance element side control voltage CV _cont is applied, and the variable resistance element side control voltage RV. so as to cancel the variation of the negative resistance due to the change in the resistance value of the variable resistor element R _V was applied to _cont, converting at least one of the level and the gain of the variable resistive element the control voltage RV _cont.

Here, as described above, the variable capacitor side control voltage CV _cont is a value depending on the characteristic unique to the vibrator X and each variable capacitor C _L and is set in advance. For this reason, when converting at least one of the level and gain of the variable resistance element side control voltage _RVcont , the conversion is performed according to the preset variable capacitance element side control voltage _CVcont . Therefore, the degree of conversion of at least one of the level and the gain of the variable resistance element side control voltage RV _{cont by} the control voltage conversion means 4 is a predetermined eigenvalue.

(Operation)
Next, the operation of the voltage controlled oscillator 1 having the above configuration will be described with reference to FIG.
When the voltage controlled oscillator 1 is operated, the control voltage applying means 2 applies the control voltage V _cont simultaneously to each variable capacitance element C _L and variable resistance element R _V. Specifically, the control voltage application unit 2 applies the same value of the control voltage V _cont to the variable capacitance elements C _L and the control voltage conversion unit 4 at the same time.

Hereinafter, the operation regarding each variable capacitance element C _L to which the control voltage V _cont (variable capacitance element side control voltage CV _cont ) is applied will be described.
The variable capacitance element side control voltage CV _cont applied by the control voltage application means 2 to each variable capacitance element C _L is set to the desired frequency in order to set the resonance frequency at which the vibrator X oscillates to a desired frequency. The voltage is set to a value necessary for control.
Therefore, the application of a variable capacitance element the control voltage CV _cont to the variable capacitance elements C _L, and changes the capacitance value of the variable capacitance elements C _L, the oscillation frequency of the oscillator X oscillates, the desired frequency .

Next, the operation relating to the control voltage conversion means 4 to which the control voltage V _cont is applied will be described.
The control voltage conversion means 4 converts the control voltage V _cont applied by the control voltage application means 2 and applies the converted variable resistance element side control voltage RV _cont to the variable resistance element R _V. Specifically, to cancel the variation of the negative resistance due to the change in the resistance value of the variable capacitance elements C _L variation of the negative resistance due to the change of the capacitance value of the variable resistor element R _V, a variable resistor At least one of the level and gain of the element side control voltage RV _cont is converted.

Here, the capacitance value of each variable capacitance element C _L increases as the voltage of the variable capacitor side control voltage CV _cont increases, decreases as the voltage of the variable capacitor side control voltage CV _cont decreases.
On the other hand, the resistance value of the variable resistor element R _V decreases as the voltage value of the variable resistive element the control voltage RV _cont increases, increases as the voltage value of the variable resistive element the control voltage RV _cont decreases.
Therefore, the application of a variable resistive element the control voltage RV _cont to the variable resistive element R _V, the resistance value of the variable resistor element R _V is changed, the change of the negative resistance due to the change of the capacitance value of each variable capacitance element C _L minutes and variation of the negative resistance due to the change in the resistance value of the variable resistor element R _V is canceled, the change of the negative resistance is suppressed.

More specifically, the control voltage V _cont is increased, the voltage value of the variable capacitance element the control voltage CV _cont increases, increasing the capacitance value of the variable capacitance elements C _L, the negative resistance is decreased. On the other hand, when the control voltage V _cont increases and the voltage value of the variable resistance element side control voltage RV _cont increases, the resistance value of the variable resistance element R _V decreases and the negative resistance increases. As a result, the decrease in the negative resistance due to the increase in the capacitance value of each variable capacitance element C _L and the increase in the negative resistance due to the decrease in the resistance value of the variable resistance element R _V are offset. It is suppressed.

Also, as the control voltage converting means 4, to offset the respective variable capacitance elements C _L variation of the negative resistance due to the change in the resistance value of the negative resistance change of the variable resistor element R _V due to the change of the capacitance value of to convert at least one of the level and the gain of the variable resistive element the control voltage RV _cont, the converted variable resistive element the control voltage RV _cont, it applied to the variable resistive element R _V. As a result, the change in the negative resistance due to the change in the capacitance value of the variable capacitance element C _L and the change in the negative resistance due to the change in the resistance value of the variable resistance element R _V are more effectively canceled out. Is more efficiently suppressed.

(Effects of the first embodiment)
The effects of this embodiment are listed below.
(1) the voltage controlled oscillator 1 of the present embodiment, the control voltage applying means 2, and the variable capacitance element C _L the capacitance value by the control voltage V _cont to be applied is changed, the resistance value is changed by the control voltage V _cont is applied A control voltage V _cont is simultaneously applied to the variable resistance element R _V to be applied.
Therefore, a change in negative resistance due to a change in the capacitance value of the variable capacitance element C _L and a change in negative resistance due to a change in the resistance value of the variable resistance element R _V caused by applying the control voltage V _cont Can be offset, and the change in the negative resistance caused by the change in the control voltage _Vcont can be suppressed.
As a result, it is possible to suppress a change in negative resistance that occurs due to a change in the control voltage V _cont without adding new parts. As a result, it is possible to suppress an increase in the number of parts and suppress an increase in cost, and it is possible to obtain a stable oscillation and a wide frequency variable range.

(2) In the voltage controlled oscillator 1 of the present embodiment, the control voltage conversion means 4 causes the change in the negative resistance due to the change in the capacitance value due to the application of the control voltage _Vcont and the change in the negative resistance due to the change in the resistance value. _So that at least one of the level and gain of the variable resistance element side control voltage _RVcont is converted to a value different from the variable capacitance element side control voltage _CVcont .
Therefore, the change in the negative resistance due to the change in the capacitance value of the variable capacitance element caused by applying the variable capacitance element side control voltage CV _cont and the variable resistance caused by applying the variable resistance element side control voltage RV _cont It becomes possible to more efficiently cancel out the change in the negative resistance due to the change in the resistance value of the element.
As a result, the negative resistance change caused by the change in the control voltage V _cont can be more efficiently suppressed as compared with the voltage controlled oscillator 1 having the configuration not including the control voltage conversion means 4. .

(Application examples)
Hereinafter, application examples of this embodiment will be listed.
(1) Although the voltage controlled oscillator 1 of the present embodiment has the configuration including the control voltage conversion means 4, the configuration is not limited thereto, and the control voltage conversion means 4 may not be provided.
(2) In the voltage controlled oscillator 1 of the present embodiment, only the amplifier circuit A is connected in parallel to the vibrator X, but the present invention is not limited to this. That is, for example, as shown in FIG. 2, the amplifier circuit A is configured to include a resistance element R _O for determining the operating point, and the amplifier circuit A and the resistance element R _O are connected in parallel to the vibrator X. It is good also as the structure currently made. FIG. 2 is a diagram illustrating a modification of the present embodiment.

(Second embodiment)
Next, a second embodiment of the present invention (hereinafter referred to as “the present embodiment”) will be described with reference to the drawings.
(Constitution)
First, the configuration of the present embodiment will be described with reference to FIG. Detailed description of the same configuration as that of the first embodiment described above will be omitted.
FIG. 3 is a diagram showing a configuration of the voltage controlled oscillator 1 of the present embodiment.
As shown in FIG. 3, the voltage controlled oscillator 1 according to the present embodiment includes a variable voltage element C _L and a variable resistance element R _V formed by MOS transistors, and control voltage conversion means. Except for this point, it has the same configuration as that of the first embodiment described above. In FIG. 3, a MOS transistor forming each variable capacitance element C _L is described as “MOSC”, and a MOS transistor forming the variable resistance element R _V is described as “MOSR”.

The MOS transistor forming each variable capacitance element C _L and the MOS transistor forming the variable resistance element R _V are the MOS transistors having the same or substantially the same change in channel due to application of the control voltage V _cont. .
Both MOS transistors forming each variable capacitance element _CL are formed by short-circuiting the source and drain.
Further, in the MOS transistor forming each variable capacitance element C _L , a channel is formed by applying the control voltage V _cont , and the capacitance value changes according to the change in the channel. Specifically, the capacity value increases as the number of channels increases, and the capacity value decreases as the number of channels decreases.

The MOS transistor forming the variable resistance element R _V includes a resistance element R ₂ for controlling the voltage flowing through the MOS transistor in a state where the resistance value is minimized. Thus, the MOS transistor forming the variable resistance element R _V and the resistance element R ₂ are connected in parallel between the vibrator X and the output side of the amplifier circuit A.
In the MOS transistor forming the variable resistance element R _V , a channel is formed by applying the control voltage V _cont , and the resistance value changes according to the change in the channel. Specifically, the resistance value decreases as the channel increases, and the resistance value increases as the channel decreases.
Other configurations are the same as those of the first embodiment described above.

(Operation)
Next, the operation of the voltage controlled oscillator 1 having the above configuration will be described with reference to FIG. In the following description, differences from the above-described first embodiment will be mainly described.
When the voltage controlled oscillator 1 is operated, the control voltage applying means 2 applies the control voltage V _cont having the same value simultaneously to each variable capacitance element C _L and variable resistance element R _V.
Applying a control voltage V _cont to the variable capacitance elements C _L, and changes the capacitance value of the variable capacitance elements C _L, the oscillation frequency of the oscillator X oscillates, the desired frequency.
Here, the MOS transistor forming each variable capacitance element C _L increases in capacitance value as the channel is formed by application of the control voltage V _cont and decreases as the channel decreases.

On the other hand, in the MOS transistor forming the variable resistance element R _V , the resistance value decreases as the number of channels formed by applying the control voltage V _cont increases, and the resistance value increases as the number of channels decreases.
Therefore, when the control voltage V _cont having the same value is simultaneously applied to each variable capacitance element C _L and variable resistance element R _V , the change in the negative resistance due to the change in the capacitance value of each variable capacitance element C _L and the variable resistance element R The change in the negative resistance due to the change in the resistance value of _V is canceled out, and the change in the negative resistance is suppressed.

More specifically, the control voltage V _cont is increased, the channel formed by the application of a control voltage V _cont is increased, increasing the capacitance value of the variable capacitance elements C _L, the negative resistance is decreased. On the other hand, when the control voltage V _cont increases and the number of channels formed by applying the control voltage V _cont increases, the resistance value of the variable resistance element R _V decreases and the negative resistance increases. As a result, the decrease in the negative resistance due to the increase in the capacitance value of each variable capacitance element C _L and the increase in the negative resistance due to the decrease in the resistance value of the variable resistance element R _V are offset. It is suppressed.

Here, in this embodiment, each variable capacitance element C _L and variable resistance element R _V are formed of MOS transistors having the same or substantially the same change in channel due to application of the control voltage V _cont .
As a result, the change characteristic of the capacitance value of the variable capacitance element C _L and the change characteristic of the resistance value of the variable resistance element R _V due to the application of the control voltage V _cont are the same or substantially the same, so the control voltage V _cont is shared. Can be realized.
Other operations are the same as those in the first embodiment described above.

(Effect of the second embodiment)
Hereinafter, effects of the present embodiment will be described.
(1) In the voltage controlled oscillator 1 of the present embodiment, the variable capacitance element C _L and the variable resistance element R _V are formed by MOS transistors having the same or substantially the same change in channel due to application of the control voltage V _cont .
Therefore, the control by the application of the voltage V _cont, variable capacitance elements C _L change characteristics of the resistance value of the change characteristics and the variable resistive element R _V capacitance value becomes equal to or substantially equal, the variable capacitance element C _L and the variable resistor element It becomes possible to share the control voltage applied to R _V.
As a result, the control voltage V _cont can be set to a value necessary for controlling the oscillation frequency at which the vibrator X oscillates to a desired frequency and to suppress negative resistance. It becomes easy.

(Application examples)
Hereinafter, application examples of this embodiment will be described.
(1) In the voltage controlled oscillator 1 of the present embodiment, the MOS transistor (MOSC) forming the variable capacitance element C _L is formed by short-circuiting the source and drain, but the present invention is not limited to this. . That is, for example, as shown in FIG. 4, the MOS transistor (MOSC) forming the variable capacitance element C _L is in a state where one of the source and the drain is opened without short-circuiting the source and the drain. It may be formed. FIG. 4 is a diagram illustrating a modification of the present embodiment.

(Third embodiment)
Next, a third embodiment of the present invention (hereinafter referred to as “the present embodiment”) will be described with reference to the drawings.
(Constitution)
First, the configuration of the present embodiment will be described with reference to FIG. Detailed description of the same configuration as that of the first embodiment described above will be omitted.
FIG. 5 is a diagram showing a configuration of the voltage controlled oscillator 1 of the present embodiment.
As shown in FIG. 5, the voltage controlled oscillator 1 of this embodiment forms one of the two variable capacitance elements and the variable resistance element in the second embodiment described above by sharing one MOS transistor. Except for the point and the point that the control voltage conversion means is not provided, the configuration is the same as that of the first embodiment described above.

In FIG. 5, the MOS transistor forming one of the two variable capacitance elements and the variable resistance element is referred to as “MOSRC”, and the MOS transistor forming the other of the two variable capacitance elements. Is described as “MOSC”. In the following description, an element formed by sharing one MOS transistor and sharing a variable resistance element with one of two variable capacitance elements will be referred to as “shared element E ₁ ”. Similarly, the other element of the two variable capacitance elements is referred to as “single element E ₂ ”.

The MOS transistor forming the shared element E ₁ and the MOS transistor forming the single element E ₂ are, for example, MOS transistors whose channel changes due to application of the control voltage V _cont are the same or substantially the same. .
The MOS transistor forming the shared element E ₁ includes a resistance element R ₂ for controlling the voltage flowing through the MOS transistor in a state where the resistance value is minimized. As a result, the MOS transistor forming the shared element E ₁ and the resistor element R ₂ are connected in parallel between the vibrator X and the output side of the amplifier circuit A.

In the MOS transistor forming the shared element E ₁ , a channel is formed by applying the control voltage V _cont , and the capacitance value and the resistance value change according to the change in the channel. Specifically, as the channel increases, the capacitance value increases and the resistance value decreases, and as the channel decreases, the capacitance value decreases and the resistance value increases.
In this embodiment, as shown in FIG. 5, one of the two variable capacitance elements in the second embodiment described above and all of the variable resistance elements are formed by sharing one MOS transistor.

The MOS transistor forming the single element E ₂ is formed by short-circuiting the source and drain.
In the MOS transistor forming the single element E ₂ , a channel is formed by applying the control voltage V _cont , and the capacitance value changes according to the change in the channel. Specifically, the capacity value increases as the number of channels increases, and the capacity value decreases as the number of channels decreases.
Other configurations are the same as those of the first embodiment described above.

(Operation)
Next, the operation of the voltage controlled oscillator 1 having the above configuration will be described with reference to FIG. In the following description, differences from the above-described second embodiment will be mainly described.
When the voltage controlled oscillator 1 is operated, the control voltage applying means 2 applies the control voltage V _cont having the same value simultaneously to the shared element E ₁ and the single element E ₂ .
Applying a control voltage V _cont to the shared elements E ₁ and a single element E _2, and changes the capacitance value of the shared elements E ₁ and a single element E _2, the oscillation frequency of the oscillator X oscillates the desired frequency It becomes.
Here, in the MOS transistor forming the shared element E ₁ , the capacitance value increases and the resistance value decreases as the number of channels formed by application of the control voltage V _cont increases, and the capacitance value decreases as the number of channels decreases. As the value decreases, the resistance value increases.

On the other hand, in the MOS transistor forming the single element E ₂ , the capacitance value increases as the number of channels formed by application of the control voltage V _cont increases, and the capacitance value decreases as the number of channels decreases.
Therefore, when the control voltage V _cont having the same value is simultaneously applied to the shared element E ₁ and the single element E ₂ , the change in the negative resistance due to the change in the capacitance value and resistance value of the shared element E ₁ and the single element E _2. The change in the negative resistance due to the change in the capacitance value is offset, and the change in the negative resistance is suppressed.

As a result, the change in the negative resistance due to the change in the capacitance value and the resistance value of the shared element E ₁ and the change in the negative resistance due to the change in the capacitance value of the single element E ₂ are canceled out. Is suppressed.
Here, in this embodiment, one of the two variable capacitance elements in the second embodiment described above and the variable resistance element are formed by sharing one MOS transistor (“MOSRC”).
Accordingly, since one MOS transistor forms a variable capacitance element and a variable resistance element, there is no problem that matching between the variable capacitance element and the variable resistance element is deteriorated. The operation can be stabilized.
Other operations are the same as those in the first embodiment described above.

(Effect of the third embodiment)
Hereinafter, effects of the present embodiment will be described.
(1) In the voltage controlled oscillator 1 of the present embodiment, the variable capacitance element and the variable resistance element are formed by sharing one MOS transistor.
For this reason, since one MOS transistor forms a variable capacitance element and a variable resistance element, there is no problem that matching between the variable capacitance element and the variable resistance element deteriorates. The operation can be stabilized.
As a result, it is possible to reduce the number of parts and reduce costs, and it is possible to obtain stable oscillation and a wide frequency variable range.

(Application examples)
Hereinafter, application examples of this embodiment will be described.
(1) In the voltage controlled oscillator 1 of the present embodiment, all of the variable capacitance element and the variable resistance element are formed by sharing one MOS transistor, but the present invention is not limited to this. That is, for example, as shown in FIG. 6, a part of the variable capacitance element C _L and the variable resistance element R _V may be formed by sharing one MOS transistor. FIG. 6 is a diagram illustrating a modification of the present embodiment.

It is a figure which shows the structure of the voltage controlled oscillator of 1st embodiment of this invention. It is a figure which shows the modification of 1st embodiment of this invention. It is a figure which shows the structure of the voltage controlled oscillator of 2nd embodiment of this invention. It is a figure which shows the modification of 2nd embodiment of this invention. It is a figure which shows the structure of the voltage controlled oscillator of 3rd embodiment of this invention. It is a figure which shows the modification of 3rd embodiment of this invention. It is a figure which shows the structure of the conventional voltage controlled oscillator. It is a figure which shows the structure of the equivalent circuit of a vibrator | oscillator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Voltage control oscillator 2 Control voltage application means 4 Control voltage conversion means 6 Connection terminal A Amplifying circuit C _L Variable capacity element R _V Variable resistance element X Oscillator V _cont Control voltage CV _cont Variable capacity element side control voltage RV _cont Variable resistance element Side control voltage MOSC MOS transistor forming variable capacitance element C _L MOSR forming MOS variable resistance element R _V MOSRC forming MOS variable resistance element and MOS transistor forming variable resistance element E ₁ shared element E ₂ single element R _O resistance element R ₁ resistance element

Claims (3)

An amplifier circuit connected in parallel to the vibrator, a variable capacitance element that is connected to the input side of the amplifier circuit and whose capacitance value changes according to the applied control voltage, and the output circuit that is connected to and applied to the output side of the amplifier circuit A variable resistance element that is connected between at least one of the variable capacitance elements whose capacitance value is changed by a control voltage and the output side of the vibrator and the amplification circuit and whose resistance value is changed by the applied control voltage; Control voltage application means for simultaneously applying the control voltage to the variable capacitance element and the variable resistance element ,
It said variable capacitance element and the variable resistance element, a voltage controlled oscillator variation of the channel by application of the control voltage is characterized that you formed in the same or substantially the same MOS transistor. An amplifier circuit connected in parallel to the vibrator, a variable capacitance element that is connected to the input side of the amplifier circuit and whose capacitance value changes according to the applied control voltage, and the output circuit that is connected to and applied to the output side of the amplifier circuit A variable resistance element that is connected between at least one of the variable capacitance elements whose capacitance value is changed by a control voltage and the output side of the vibrator and the amplification circuit and whose resistance value is changed by the applied control voltage; Control voltage application means for simultaneously applying the control voltage to the variable capacitance element and the variable resistance element,
A voltage-controlled oscillator, wherein the variable capacitance element and the variable resistance element are formed by sharing one MOS transistor . A variable capacitance element that is connected between the control voltage applying means and the variable resistance element and applies at least one of the level and gain of the variable resistance element side control voltage applied to the variable resistance element to the variable capacitance element Control voltage conversion means for converting to a value different from the side control voltage,
The control voltage conversion means adjusts the level and gain of the variable resistance element side control voltage so as to cancel out the change in the negative resistance due to the change in the capacitance value and the change in the negative resistance due to the change in the resistance value. The voltage controlled oscillator according to claim 1, wherein at least one of them is converted .

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