JP2000278093A - Voltage control impedance adjusting circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain voltage control while unnecessitating any special process nor applying any precise voltage to switching elements. SOLUTION: Impedance elements Z1, Z2, and Z3 are serially connected. One end of the Z1 is connected with an inner circuit. An MOS transistor M1 is connected between the end and ground as a switch. Also, an MOS transistor M2 is connected between the connection of the Z1 and the Z2 and ground as a switch, and an MOS transistor M3 is connected between the connection of the Z2 and Z3 and ground as a switch. The threshold voltages of the MOS transistors M1, M2, and M3 are made different. Thus, it is possible to move the MOS transistors M3, M2, and M1 from the off operation to the on operation in this order attending on the increase in a control voltage Vs commonly applied to each MOS transistor. As a result, the whole impedance can be changed stepwise.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an impedance circuit used in a semiconductor integrated circuit device. In particular, the present invention relates to a voltage control impedance adjustment circuit capable of adjusting an impedance value according to a control voltage value.

[0002]

2. Description of the Related Art In a semiconductor integrated circuit, resistors having various values may be provided in addition to transistors. This resistance needs to be adjusted to a predetermined value in order to keep the operation of the semiconductor integrated circuit good. Therefore, various techniques for adjusting the value of the resistance inside the semiconductor integrated circuit have been conventionally proposed.

For example, a method of arranging a plurality of resistors made of polysilicon or the like and adjusting the connection between them by wiring has been used.

In order to make adjustments with wiring external to the semiconductor integrated circuit device, it is necessary to provide a large number of terminals outside the semiconductor integrated circuit device and adjust wiring between the terminals. Also, if necessary, it is necessary to connect a resistor to the external terminal. Therefore, a great deal of trouble is required to adjust the resistance value.

[0005] Techniques for adjusting the resistance value without providing external terminals are also widely used. In this method, it is necessary to change the wiring pattern inside the semiconductor integrated circuit device in order to adjust the resistance value. As a result, it is necessary to change the design of the semiconductor integrated circuit, which also requires a great deal of trouble to adjust the resistance value. The reason is that the wiring pattern mask needs to be changed.

Further, there is also used a method in which a resistor having a predetermined shape pattern is provided in a semiconductor integrated circuit in advance, and the shape pattern of the resistor is adjusted by trimming at the final stage of the manufacturing process. This method does not require a design change, but requires a special process for trimming, which further complicates the semiconductor integrated circuit manufacturing process. Note that there is a method of burning off the wiring by high voltage instead of trimming, but this method also requires a special process.

Therefore, in recent years, there has been a demand for a circuit capable of adjusting the resistance value with the value of an external control voltage. this is,
In other words, it is a voltage control resistor circuit. The following circuit has been proposed as a circuit whose resistance can be adjusted by voltage.

For example, Japanese Patent Application Laid-Open No. Sho 60-18949 (hereinafter referred to as Japanese Patent Application Laid-Open No. 60-18949) discloses a semiconductor voltage control resistance element in which a diffusion resistance value changes according to a gate voltage. This element is an element that adjusts a so-called ON resistance of a transistor by a gate voltage.

[0009] For example, Japanese Patent Application Laid-Open No. Hei 5-267584 (hereinafter referred to as Japanese Patent Application Laid-Open No. Hei 5-267584) also discloses a semiconductor voltage control resistance element whose diffusion resistance changes depending on the gate voltage. The resistance element described here uses the source of a MOS transistor as a resistance element and attempts to adjust the connection between the source and the drain according to the gate voltage. If the source-drain becomes short-circuited due to the application of the gate voltage, the drain is connected in parallel to the source and the overall resistance decreases. Conversely, the gate voltage decreases and the source-drain becomes closer to open. For example, it is described that the drain is separated from the source, and the overall resistance value is increased.

[0010]

However, according to the technique disclosed in the above publication, a precise gate voltage must be supplied to adjust the resistance value. In particular, since the so-called source-drain resistance of a MOS transistor greatly changes before and after the threshold voltage, it is necessary to supply a precise voltage to the gate before and after the threshold voltage. As a result, a circuit that supplies a control voltage (that is, a gate voltage) requires a precise operation.

Further, also in the technique of the above-mentioned publication 2, after all, the so-called source-drain resistance of the transistor is adjusted by the gate voltage, thereby adjusting the overall resistance value. Therefore, a precise voltage must be supplied in order to adjust the resistance value, as in the publication 1.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a voltage controlled impedance adjusting circuit which does not require a special process and does not need to supply a precise voltage.

[0013]

In order to solve the above-mentioned problems, the present invention provides a method for short-circuiting a first impedance element and a first impedance element when a control voltage exceeds a first threshold voltage. A first switching element to be controlled, a second impedance element connected in series with the first impedance element, and a control voltage exceeding a second threshold voltage higher than the first threshold voltage. And a second switching element for short-circuiting a series circuit including the first impedance element and the second impedance element.

That is, the present invention employs a configuration in which two impedance elements are connected in series, and a switching element is connected in parallel to each impedance element.

In particular, in the present invention, the threshold voltages of the two first and second switching elements are different. Therefore, a single control voltage is applied to these switching elements, and the voltage at which the operation shifts from the OFF operation to the ON operation can be different for each switching element. As a result, only one switching element can be turned on, or both two switching elements can be turned on, depending on the value of the control voltage.

As a result, a voltage-controlled impedance adjusting circuit that can adjust the impedance of the series circuit including the first impedance element and the second impedance element according to the value of the control voltage is obtained.

Further, since the threshold voltages of the switching elements are made different, the impedance value can be changed stepwise with respect to the change of the control voltage. Therefore, high accuracy is not required for the value of the control voltage.

Although the above-described invention uses two impedance elements and two switching elements, the present invention is generalized to a circuit using N impedance elements and N switching elements. be able to. Here, N is a positive integer.

That is, according to the present invention, N series-connected N
The first to N-th impedance element groups and the N first to N-th switching element groups are included. Further, according to the present invention, the Mth switching element among the N switching elements short-circuits the first impedance element to the Mth impedance element when the control voltage exceeds the Mth threshold voltage. Let it. At this time, the threshold values of the first to Nth switching elements are different from each other.

As a result, it is possible to obtain a voltage-controlled impedance adjusting circuit capable of adjusting the impedance of the series circuit including the N impedance element groups according to the value of the control voltage. Here, N is a positive integer, and M is a positive integer from 1 to N.

Further, in the present invention, similarly to the previous invention,
The feature is that high accuracy is not required for the control voltage.

Next, another invention provides a first impedance element, a first switching element for short-circuiting the first impedance element when a value of the control voltage exceeds a predetermined threshold voltage, A second impedance element connected in series with the first impedance element and a second voltage when the control voltage exceeds a total voltage obtained by adding a predetermined threshold voltage and a conduction voltage of the first switching element. And a second switching element for short-circuiting the impedance element.

Thus, the present invention differs from the first invention in that each switching element short-circuits only one corresponding impedance element.

In the present invention, the switching elements are connected in series, so to speak, so that the effective value of the control voltage for each switching element depends on its bias condition. As a result, even if a common control voltage is applied to each switching element, the control voltage exceeds the threshold value for the first switching element,
A situation arises in which the control voltage does not exceed the threshold voltage for the switching element.

As a result, it is possible to control the number of switching elements that are turned ON by the value of the control voltage. For this reason, a voltage-controlled impedance adjustment circuit capable of adjusting the impedance of a series circuit including the first impedance element and the second impedance element by the value of the control voltage is obtained.

As described above, according to the present invention, the impedance value can be changed stepwise with respect to the change in the control voltage without changing the threshold voltage.
Therefore, high accuracy is not required for the value of the control voltage as in the above-described invention.

Although the above invention uses two impedance elements and two switching elements, the present invention can be generalized to a circuit using N impedance elements and N switching elements. . here,
N is a positive integer.

That is, according to the present invention, N series-connected N
The first to N-th impedance element groups and the N first to N-th switching element groups are included. Further, according to the present invention, the M-th switching element in the N switching element groups is configured such that the control voltage is obtained by adding a predetermined threshold voltage and the first to (M−1) -th total conduction voltages. When the measured voltage is exceeded, the M-th impedance element is short-circuited.

As a result, a voltage controlled impedance adjusting circuit capable of adjusting the impedance of the series circuit composed of the N impedance element groups by the value of the control voltage is obtained. Here, N is a positive integer, and M is a positive integer from 1 to N.

Further, also in the present invention, the impedance value can be changed stepwise with respect to the change of the control voltage. Therefore, high accuracy is not required for the value of the control voltage as in the above-described inventions.

According to the above-described invention, the impedance can be adjusted by the value of the control voltage. Still another invention is characterized in that, in the above-described configuration, the impedance element is a resistance element. According to this configuration, the resistance value can be adjusted by the value of the control voltage.

According to another aspect of the present invention, in the above configuration,
The impedance element is an inductance element. According to this configuration, the inductance value can be adjusted according to the value of the control voltage.

Further, in another aspect of the present invention,
The impedance element is a capacitance element. According to this configuration, the capacitance value (capacitance value) can be adjusted by the value of the control voltage.

Still another aspect of the invention is characterized in that, in each of the above-described configurations, the switching element is a MOS transistor, and the control voltage is applied to the gate of the MOS transistor. According to this configuration, since the control voltage is applied to the gate, the value of the gate voltage can be adjusted by the value of the control voltage, and the O
The N / OFF state can be controlled.

Another aspect of the invention is characterized in that, in each of the above-described configurations, the switching element is a bipolar transistor, and the control voltage is applied to the base of the bipolar transistor. According to this configuration, since the control voltage is applied to the base, the value of the base current can be adjusted by the value of the control voltage, and the ON / OFF state of the bipolar transistor can be controlled.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment] FIG. 1 is a circuit diagram of a voltage-controlled impedance adjusting circuit according to a preferred embodiment of the present invention. In this figure, the impedance elements Z1, Z2, Z3 connected in series may be any of a resistance element, an inductance element, and a capacitance element. Further, impedance elements Z1, Z2,
Z3 may be a different type of element, for example, a combination circuit of a resistance element and an inductance element.

One end of the impedance element Z1 is connected to an internal circuit of the semiconductor integrated circuit device. A MOS transistor M1 is connected between one end and ground, and the connection between this one end and ground is turned on / off.
Is operating as a switch.

A MOS transistor M2 is connected between the connection point between the impedance elements Z1 and Z2 and the ground, and operates as a switch for turning on / off the connection between the connection point and the ground. are doing.

Further, a MOS transistor M3 is connected between the connection point between the impedance element Z2 and the impedance element Z3 and the ground, and operates as a switch for turning on / off the connection between the connection point and the ground. are doing.

The control voltage Vs is applied to the gate terminals of the MOS transistors M1, M2 and M3 as switches.
Is commonly applied.

The characteristics of the first embodiment are as follows.
This means that the threshold voltages of the MOS transistors M1, M2 and M3 are all different. Specifically, in the first embodiment, the threshold voltage of MOS transistor M3 is, for example, 0.7 V, and MOS transistor M2
Is 0.8 V, for example, and the threshold voltage of MOS transistor M1 is 0.9 V, for example.

In the first embodiment, since the threshold voltages of the MOS transistors are different,
As the control voltage is increased, the MOS transistor M
1, M2, and M3 can be sequentially shifted from the OFF operation to the ON operation.

Hereinafter, a change in impedance of the voltage controlled impedance adjusting circuit according to the first embodiment will be described with reference to a graph. In the following description, the impedance element Z1,
Z2 and Z3 are all resistance elements, and their values are all 1
An example of 00 ohm will be described.

FIG. 2 is an explanatory diagram showing a graph representing an impedance change of the voltage controlled impedance adjusting circuit according to the first embodiment. In this graph, the vertical axis represents the resistance value of the entire voltage control impedance adjustment circuit, and the horizontal axis represents the value of the control voltage Vs.

First, when the control voltage Vs is lower than 0.7 V, all the MOS transistors M1, M2, M3 are in the OFF state. As a result, the overall impedance (resistance value) of the voltage control impedance adjustment circuit is Z1 + Z
2 + Z3Ω, that is, 300Ω.

Then, the control voltage Vs rises from 0 V,
When the voltage reaches 0.7 V, the MOS transistor M3 shifts to the ON operation, and the impedance element Z3 is short-circuited. As a result, the overall impedance (resistance value) of the voltage control impedance adjustment circuit becomes Z1 + Z2Ω, that is, 200Ω. The manner in which the resistance value changes stepwise in this manner is shown in the graph of FIG.

Further, the control voltage Vs increases to 0.8 V
, The MOS transistor M3 and the MOS transistor M3
The transistor M2 shifts to the ON operation, and the impedance element Z2 as well as the impedance element Z3 is short-circuited. As a result, the overall impedance (resistance value) of the voltage control impedance adjustment circuit is Z1Ω, that is, 10Ω.
It becomes 0Ω. This situation is also shown in the graph of FIG.

When the control voltage Vs further rises and becomes 0.9 V or more, all the MOS transistors M1, M2 and M3 shift to the ON operation, and the impedance elements Z1 and Z
2, Z3 are all short-circuited. As a result, the overall impedance (resistance value) of the voltage control impedance adjustment circuit becomes almost 0Ω (see the graph of FIG. 2).

As described above, in the first embodiment,
The threshold voltage of a MOS transistor as a switching element is different for each of the MOS transistors M1, M2, and M3. Therefore, the MOS transistors M1, M2, and M3 can be sequentially shifted from the OFF operation to the ON operation only by using a single control voltage. As a result, according to the first embodiment, the control voltage Vs
Can be obtained in which the resistance value can be changed stepwise according to the value of.

Further, in the first embodiment, since the resistance value is changed stepwise, even if the control voltage slightly fluctuates, the resistance value can be accurately set to a desired value. . For example, in the above example, the control voltage is set to 0.
If it is in the voltage range of 7V to 0.8V, the resistance value is 200
Ω. That is, when the control voltage is set to 0.75 V, the resistance value becomes 200Ω even if the control voltage of 0.77 V is generated due to an error. In other words, it can be said that the circuit of the first embodiment is strong against the voltage fluctuation of the control voltage.

Further, in the first embodiment, since the resistance value is adjusted with a single control voltage, the resistance value can be adjusted only by providing a single control voltage application terminal outside the semiconductor integrated circuit device. Is adjustable.

Further, it is possible to adjust the resistance value without adding any device to the substrate on which the semiconductor integrated circuit device is mounted.

In the first embodiment, the MOS
Because transistors are used as switching elements,
No large area is consumed on the semiconductor integrated circuit device.
As a result, space can be saved.

In the first embodiment, a MOS transistor is used as a switching element. However, any other means that can be used as a switching element and that can have different threshold voltages can be used. Any other means may be used. For example, it is also preferable to use a bipolar transistor.

In the first embodiment, the operation has been described with respect to an example in which a resistance element is used as an impedance element. However, it is also preferable to use a capacitance element (capacitor) or an inductance element (coil) as the impedance element. .

It is also preferable to use a circuit combining these different types of elements as an impedance element.

Second Embodiment In the first embodiment, three impedance elements and three switching elements are used. However, any number of two or more switching elements may be used. For example, a circuit diagram when two impedance elements and two switching elements are used is shown in FIG. FIG. 4 is a graph showing the relationship between the control voltage Vs of the circuit shown in FIG. 3 and the overall resistance.
Are shown in FIG. In the graph of FIG. 4, the vertical axis represents the entire resistance value as in FIG. 2, and the unit is Ω. The horizontal axis represents the control voltage Vs, and the unit is V.

The operation principle of the circuits shown in FIGS. 3 and 4 is as follows.
This is essentially the same as the first embodiment. Further, the operation is obvious from the graph of FIG. 4, and therefore the description is omitted because it is based on the first embodiment.

[Third Embodiment] FIG. 5 is a circuit diagram of a voltage-controlled impedance adjusting circuit according to a third embodiment of the present invention. In this figure, impedance elements Z1, Z2, Z3 connected in series are:
As in the first embodiment, any of a resistance element, an inductance element, and a capacitance element may be used. Further, impedance elements Z1, Z2, and Z3 are different types of elements,
For example, a combination circuit of a resistance element and an inductance element may be used.

One end of the impedance element Z1 is connected to an internal circuit of the semiconductor integrated circuit device. A MOS transistor M1 is connected between both ends of the impedance element Z1.
Is connected. This MOS transistor M1 is ON
If operated, the impedance element Z1 is short-circuited. That is, the MOS transistor M1 operates as a switch for short-circuiting the impedance element Z1.

A MOS transistor M2 is connected between both ends of the impedance element Z2. This M
When the OS transistor M2 is turned on, the impedance element Z2 is short-circuited. That is, the MOS transistor M2 operates as a switch for short-circuiting the impedance element Z2.

One end of the impedance element Z3 is connected to the impedance element Z2, and the other end is connected to the ground. And the impedance element Z
As in the first and second embodiments, a MOS transistor M3 is connected between both ends of the impedance element Z3. This M
When the OS transistor M3 is turned on, the impedance element Z3 is short-circuited. That is, the MOS transistor M3 operates as a switch for short-circuiting the impedance element Z3.

The control voltage Vs is applied to the gate terminals of the MOS transistors M1, M2 and M3 as switches.
Is commonly applied.

In the third embodiment, unlike the first embodiment, MOS transistors M1 and M
2. It is not necessary that the threshold voltages of M3 are different from each other. Hereinafter, description will be made assuming that the threshold voltages of the MOS transistors M1, M2, and M3 are all 0.7V.

Hereinafter, the impedance change of the voltage controlled impedance adjusting circuit according to the third embodiment will be described with reference to a graph. In the following description, the impedance element Z1,
Z2 and Z3 are all resistance elements, and their values are all 1
An example of 00 ohm will be described.

FIG. 6 is an explanatory diagram showing a graph representing an impedance change of the voltage controlled impedance adjusting circuit according to the third embodiment. In this graph, the vertical axis represents the resistance value of the entire voltage control impedance adjustment circuit, and the horizontal axis represents the value of the control voltage Vs.

First, when the control voltage Vs is lower than 0.7 V, all the MOS transistors M1, M2, M3 are in the OFF state. As a result, the overall impedance (resistance value) of the voltage control impedance adjustment circuit is Z1 + Z
2 + Z3Ω, that is, 300Ω.

Then, the control voltage Vs rises from 0V,
When the voltage reaches 0.7 V, the MOS transistor M3 shifts to the ON operation, and the impedance element Z3 is short-circuited. Since the source terminal of the MOS transistor M2 is floating above the ground by the voltage drop between the source and the drain of the MOS transistor M3, the operation does not shift to the ON operation. That is, the voltage between the source and the gate of the MOS transistor M2 at this point is changed from 0.7V to M
The voltage value is lower by a voltage drop between the source and the drain of the OS transistor M3, that is, a voltage value lower than 0.7V. Note that this voltage drop voltage is hereinafter represented by ΔV.

As a result, the overall impedance (resistance value) of the voltage control impedance adjusting circuit is Z1 + Z2Ω,
That is, it becomes 200Ω. The manner in which the resistance value changes in this way is shown in the graph of FIG.

Further, the control voltage Vs increases to 0.7 V
+ ΔV, in addition to the MOS transistor M3, M
The OS transistor M2 shifts to the ON operation, and the impedance element Z2 as well as the impedance element Z3 is short-circuited. ΔV depends on the characteristics of the MOS transistor, but generally takes a very small value.

As a result, the entire impedance (resistance value) of the voltage control impedance adjustment circuit becomes Z1Ω, that is, 100Ω. This situation is also shown in the graph of FIG.

The control voltage Vs further rises to 0.7 V +
(2 × ΔV), the MOS transistors M1 and M
2 and M3 all shift to the ON operation, and all the impedance elements Z1, Z2 and Z3 enter a short-circuit state. As a result, the overall impedance (resistance value) of the voltage control impedance adjustment circuit becomes almost 0Ω (see the graph of FIG. 6).

As described above, in the third embodiment,
MOS transistors as switching elements are connected in series. Therefore, it is possible to sequentially shift each MOS transistor from the OFF operation to the ON operation while applying a single control voltage to each MOS transistor in common. As a result, according to the third embodiment, the control voltage V
A circuit capable of changing the resistance value stepwise according to the value of s is obtained.

In the third embodiment, since the resistance value is changed stepwise, even if the control voltage slightly fluctuates, the resistance value can be accurately set to a desired value. Is the same as in the first embodiment.
That is, it can be said that the circuit of the third embodiment is strong against the voltage fluctuation of the control voltage.

In the third embodiment, similarly to the first embodiment, the resistance can be adjusted only by providing a single control voltage application terminal outside the semiconductor integrated circuit device.

Further, similarly to the first embodiment, the resistance value can be adjusted without adding any device to the substrate on which the semiconductor integrated circuit device is mounted. Similarly, space can be saved as a result.

In the third embodiment, a switching element other than a MOS transistor can be used.

In particular, in the third embodiment, it is not always necessary to make the threshold values different from those in the first and second embodiments, so that there is an effect that the manufacturing process is not complicated. .

Further, as in the first and second embodiments, it is preferable to use a capacitance element (capacitor) or an inductance element (coil) other than a resistance element as the impedance element.

Fourth Embodiment In the third embodiment, three impedance elements Z and three switching elements M are used. However, any number of two or more switching elements may be used. For example, FIG. 7 shows a circuit diagram in the case of using two each of the above elements. FIG. 8 is a graph showing the relationship between the control voltage Vs of the circuit shown in this figure and the overall resistance. In the graph of FIG. 8, the vertical axis represents the entire resistance value, as in FIG. 2, and the unit is Ω. The horizontal axis represents the control voltage Vs, and the unit is V.

The operating principles and effects of the circuits shown in FIGS. 7 and 8 are essentially the same as in the third embodiment.

[Application Examples] As described above, Embodiments 1, 2,
3 and 4, the circuits whose impedance can be adjusted by the control voltage have been described. This circuit can be used as a semi-fixed impedance circuit in a semiconductor integrated circuit device by setting a control voltage in advance. Further, by adopting a configuration in which the control voltage can be changed, the semiconductor integrated circuit device can be used as a circuit that changes an impedance value during operation.

For example, when the impedance is a resistance, it can be used as a semi-fixed resistor, or can be used as a volume (variable resistor) such as a so-called volume control.

Further, in each of the above-described embodiments, the example of each of the two or more impedance elements and the switching element has been described. However, one each may be used. Further, as shown in FIG. 9, the system of the first and second embodiments may be combined with the systems of the third and fourth embodiments.

[0086]

As described above, according to the present invention, there is provided a voltage controlled impedance adjusting circuit in which the impedance value changes stepwise in response to a change in the control voltage. Therefore, it is possible to prevent the impedance value from fluctuating in response to a minute fluctuation in the control voltage. As a result, according to the present invention, a high-precision control voltage is not required, and a circuit capable of adjusting the impedance value with high accuracy even when the control voltage is generated by a simple circuit is obtained.

In particular, when the impedance value is a resistance, it can be used as a semi-fixed resistor or a variable resistor provided inside the semiconductor integrated circuit device. Further, when the impedance value is an inductance, it can be used as a semi-fixed inductor or a variable inductor provided inside the semiconductor integrated circuit device. When the impedance value is a capacitance, it can be used as a semi-fixed capacitor or a variable capacitor provided inside the semiconductor integrated circuit device.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a voltage-controlled impedance adjustment circuit according to a first embodiment;

FIG. 2 is an explanatory diagram of a graph illustrating an operation of the voltage controlled impedance adjusting circuit according to the first exemplary embodiment;

FIG. 3 is a circuit diagram of a voltage controlled impedance adjustment circuit according to a second exemplary embodiment;

FIG. 4 is an explanatory diagram of a graph illustrating an operation of the voltage controlled impedance adjusting circuit according to the second exemplary embodiment;

FIG. 5 is a circuit diagram of a voltage-controlled impedance adjusting circuit according to a third embodiment;

FIG. 6 is an explanatory diagram of a graph illustrating an operation of the voltage controlled impedance adjusting circuit according to the third exemplary embodiment;

FIG. 7 is a circuit diagram of a voltage-controlled impedance adjustment circuit according to a fourth embodiment;

FIG. 8 is an explanatory diagram of a graph illustrating an operation of the voltage controlled impedance adjusting circuit according to the fourth exemplary embodiment;

FIG. 9 shows a method according to the first and second embodiments and a method according to the third and fourth embodiments.
FIG. 4 is a circuit diagram of a voltage control impedance adjustment circuit combining the above methods.

[Explanation of symbols]

Z1, Z2, Z3 Impedance element M1, M2, M3 MOS transistor (switching element)

Claims (9)

[Claims] A first impedance element; a first switching element for short-circuiting the first impedance element when a control voltage exceeds a first threshold voltage; and a first impedance element. Second connected in series
And a series circuit comprising the first impedance element and the second impedance element when the control voltage exceeds a second threshold voltage higher than the first threshold voltage. A voltage-controlled impedance adjusting circuit, comprising: a second switching element configured to adjust the impedance of a series circuit including the first impedance element and the second impedance element according to a value of the control voltage. 2. A semiconductor device comprising: N (N is a positive integer) first to Nth impedance element groups connected in series; and N first to Nth switching element groups connected in series; The M-th (M is a positive integer greater than or equal to 1 and less than or equal to N) switching element of the number of switching elements is determined from the first impedance element when the control voltage exceeds the M-th threshold voltage. The M-th impedance element is short-circuited, the first to N-th threshold values are different from each other, and the impedance of a series circuit including the N impedance element groups can be adjusted by the value of the control voltage. Voltage control impedance adjustment circuit. 3. A first impedance element, a first switching element for short-circuiting the first impedance element when a value of a control voltage exceeds a predetermined threshold voltage, and a first impedance element The second connected in series with
A second impedance element for short-circuiting the second impedance element when the control voltage exceeds a total voltage obtained by adding the predetermined threshold voltage and the conduction voltage of the first switching element.
A voltage-controlled impedance adjustment circuit, comprising: a switching element, wherein the impedance of a series circuit including the first impedance element and the second impedance element can be adjusted by the value of the control voltage. 4. A semiconductor device comprising: N (N is a positive integer) first to N-th impedance element groups connected in series; and N first to N-th switching element groups connected in series; The M-th (M is a positive integer not less than 1 and not more than N) switching element in the switching element group is such that the control voltage is a predetermined threshold voltage and the first to M-1
When the total sum voltage of the Nth impedance element is exceeded, the Mth impedance element is short-circuited, and the impedance of the series circuit including the N impedance element groups is determined by the value of the control voltage. Adjustable voltage control impedance adjustment circuit. 5. The voltage controlled impedance adjustment circuit according to claim 1, wherein the impedance element is a resistance element. 6. The voltage controlled impedance adjustment circuit according to claim 1, wherein said impedance element is an inductance element. 7. The voltage controlled impedance adjustment circuit according to claim 1, wherein the impedance element is a capacitance element. 8. The voltage controlled impedance adjusting circuit according to claim 1, wherein the switching element is a MOS transistor, and the control voltage is applied to a gate of the MOS transistor. . 9. The voltage controlled impedance adjusting circuit according to claim 1, wherein said switching element is a bipolar transistor, and said control voltage is applied to a base of said bipolar transistor. .