JPH07273287A - Semiconductor resistance device and amplifier circuit using it - Google Patents

Abstract

PURPOSE:To obtain a semiconductor resistance without voltage dependence in a simple constitution by eliminating a change in a resistance value by changing a depletion layer so as to depend on an applied voltage. CONSTITUTION:N-wells 12, 14 are formed independently on a P-type semiconductor substrate 11, and P-type resistance regions 13, 15 are formed respectively inside the individual wells. The N-wells 12, 14 are used to be floating. Since the wells 12, 14 are floating, potentials of the wells are decided by voltages of the resistance regions, and the voltage of a P-N junction part becomes a very small forward bias. Consequently, even when the voltages of the individual resistance regions 13, 15 are changed, the voltage of the P-N junction part is not changed but is always definite, and a depletion layer is not generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor resistance device and an amplifier circuit using the same, and more particularly to a semiconductor resistance device in which the voltage dependence of diffusion resistance is reduced and an amplification circuit using the same.

[0002]

2. Description of the Related Art Generally, the configuration of an inverting amplifier circuit, which is an example of an amplifier circuit using an operational amplifier (operational amplifier), is as shown in FIG. In FIG. 2, the input signal VIN of the signal source 1 is applied to the inverting input 5 of the operational amplifier 7 via the input resistor 2, and the non-inverting input 6 thereof is given the ground potential via the resistor 3. The output 8 of the operational amplifier 7 is fed back to the inverting input 5 via the feedback resistor 4 and negatively fed back.

Such an inverting amplifier circuit has a semiconductor integrated circuit structure, and the integrated circuit structure of the input resistor 2 and the feedback resistor 4 is shown in FIG. In FIG. 3, an N type impurity diffusion region (N well) 12 is formed on one main surface of a P type semiconductor substrate 11, and P type resistance regions 13 and 15 are diffused in the N well 12. And ion implantation.

These P-type regions 13 and 15 are used as resistance regions, and the P-type region 13 is the input resistor 2 of FIG.
, And the P-type region 15 is used as the feedback resistor 4 in FIG.

In such a structure, the lowest potential of the circuit (earth potential in this example) is applied to the semiconductor substrate 11, and N
The power source 16 applies the highest potential Vcc of the circuit to the well 12. By doing so, the PN junction surface between the substrate 11 and the N well 12 and the N well 12 and the P type resistance region 1 are formed.
Since the respective PN junction surfaces with 3 and 15 are reverse biased, the resistance regions 13 and 15 are isolated from each other, so that these P-type regions 13 and 15 can be used as resistance elements. It will be.

[0006]

In the structure of FIG. 3, when the reverse bias voltage of the PN junction between the N well 12 and the resistance regions 13 and 15 changes, the width of the depletion layer changes accordingly. Therefore, the resistance values of the resistance regions 13 and 15 also change.

The problem that the change in the resistance value due to such a change in the depletion layer affects the characteristics of the inverting amplifier circuit of FIG. 2 is that when the values of the resistors 2 and 4 are equal, R2 = R4. Will be explained.

Since the inverting input 5 of the operational amplifier 7 is a virtual ground, its potential can be regarded as 0V. Therefore, the input voltage V
When IN is negative, a current of −VIN / R2 flows from the output 8 through the resistors 4 and 2 to the signal source 1. Therefore, the voltage VOUT of the output 8 becomes -VIN * R4 / R2.

Since the N well 12 is biased at the highest potential, a reverse bias voltage larger than that of the resistor 4 is applied to the resistor 2.

FIG. 4 is a graph showing the voltage dependence of the resistance. When the reverse bias voltages of the resistors 2 and 4 are V2 and V4, respectively, V2> V4, and thus R2> R4. Therefore, VOUT <-1 * VIN. Similarly, when the input voltage VIN is positive, VOUT <−1 × VIN.

FIG. 5 shows the input / output characteristics of an ideal inverting amplifier circuit.
In the conventional example, there is a problem that the input / output linearity is poor, as indicated by the solid line 51. Since the voltage dependence of resistance changes depending on the impurity concentration, it cannot be said unequivocally, but as a typical example, if VIN = 3V, VOUT
= -3.06V, 2% better than the ideal inverting amplifier circuit
Low output voltage.

As a technique for compensating for such voltage dependence of resistance, there is a technique described in Japanese Patent Laid-Open No. 4-29706. This will be described with reference to FIG. 6. N-type diffusion regions 22 and 24 are formed on a common P-type substrate 21, and the resistances 23 and 25 of the P-type region are formed in the diffusion regions 22 and 24.
Are formed respectively.

One end A of the resistor 23 is connected to the substrate 21 and the voltage VD.
Of the fixed bias power source 27 and the cathode of the variable bias power source 28 of the voltage Vn, the other end B of the resistor 23 is connected to one end C of the resistor 25, and the anode of the variable bias power source 28 is connected to the other end of the resistor 25. D is connected to the diffusion region 22, and the anode of the fixed bias power supply 27 is connected to the diffusion region 24.

When the voltage at the connection points B and C of the resistors 23 and 25 is V1, the reverse bias voltages at A and B of the resistor 23 and C and D of the resistor 25 are Vn and Vn-V, respectively.
1, VD-V1, VD-Vn. When the voltage Vn of the variable bias power source 28 increases, the reverse bias voltage of the resistor 23 increases and the reverse bias voltage of the resistor 25 decreases. Therefore, since the resistance 23 increases and the resistance 25 decreases, the series resistance of the resistances 23 and 25 does not change much. The same is true when Vn decreases.

However, although this technique is effective in the configuration of FIG. 6, it cannot be used in the circuit of FIG. 2 as described below. In FIG. 6, when Vn has a reverse polarity, the diffusion region 2
2 cannot be used in the circuit of FIG. 2 because the resistor 2 and the resistor 23 are in the forward direction and cannot have the opposite polarities. In addition, two diffusion regions (wells) are necessary to realize one resistance having no voltage dependence, which is disadvantageous in forming an integrated circuit.

In addition to this, if a thin film resistor or a polysilicon resistor is used, there is no voltage dependence so that an inverting amplifier circuit having good input / output linearity can be realized, but there is a drawback that an extra manufacturing process is required. is there.

An object of the present invention is to provide a semiconductor resistance device in which the voltage dependence of diffusion resistance is eliminated by forming only one well.

Another object of the present invention is to provide a semiconductor resistance device which eliminates the voltage dependence of the diffusion resistance with an extremely simple structure without increasing the number of manufacturing steps.

Still another object of the present invention is to provide an amplifier circuit having good linearity of input / output characteristics.

[0020]

A semiconductor resistance device according to the present invention is a semiconductor substrate of a first conductivity type, a second conductivity type impurity region formed on one main surface of the semiconductor substrate, and the impurity region. And a resistance region of the first conductivity type formed therein, the impurity region being used in a state of being electrically released.

In another semiconductor device according to the present invention, first and second impurity regions are provided in the impurity region.
And the first impurity region which is the resistance region in each of the second impurity regions.
And a second resistance region, respectively, to form the first and second resistance regions.
It is characterized in that the impurity region of is used in a released state in terms of potential.

The amplifier circuit according to the present invention is characterized in that the first resistance region serves as an input resistance of the operational amplifier and the second resistance region serves as a feedback resistance of the operational amplifier.

[0023]

When the resistance region is formed in the well formed on the semiconductor substrate, the well is used as a floating state in which the potential is released so that the PN junction between the resistance region and the well is normally in the lower order. Bias is maintained. Therefore, no matter what voltage is applied to the resistance region,
The potential of the well also changes in accordance with the voltage of the resistance region and is maintained in a low forward bias state, is not reverse biased, and a depletion layer does not occur.

As a result, the voltage dependence of the resistance disappears,
When applied to an amplifier circuit, the input / output characteristics will not be non-linear.

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention. The same parts as in FIG. 3 are designated by the same reference numerals. In FIG. 1, 2 is formed on one main surface of the P-type semiconductor substrate 11.
N wells 12 and 14 are formed.
P-type resistance regions 13 and 15 are formed in each of the wells 12 and 14 by an impurity diffusion method, an ion implantation method, or the like.

The P-type substrate 11 is supplied with the ground potential which is the lowest potential of the circuit, and the N wells 12 and 1
In this example, 4 is in a floating (potentially open) state.

Here, the saturation currents of the resistor 13 and the N well 12, and the saturation currents of the N well 12 and the PN junctions of the substrate 11 are respectively determined by Is.
1, Is2, Boltzmann constant k, electron charge q,
If the absolute temperature is T and VT = kT / q, the resistance 13
If a positive voltage is applied to the substrate 11, the voltage V1 at the PN junction between the resistor 13 and the N well 12 is expressed as V1 = VT ln {(IS1 + IS2) / IS1}.

Here, it is assumed that IS1 = IS2 and VT = 30 mV
Then, V1 becomes 21 mV, and the PN junction becomes a forward bias state (a forward bias state smaller than the threshold voltage at which the ON current of the PN junction flows). Therefore, the resistance 13
There is no depletion layer in the gate, and as a result, the voltage dependence of the resistance disappears.

At the PN junction between the N well 14 and the resistor 15, a depletion layer does not occur at all, so that the voltage dependency of the resistor also disappears.

Therefore, if the resistors 13 and 15 having the structure shown in FIG. 1 are used for the input resistor 2 and the feedback resistor 4 of the inverting amplifier circuit shown in FIG. 2, the input / output characteristics of this inverting amplifier circuit will be as shown in FIG.
Thus, it exhibits almost ideal linearity as indicated by the broken line 52 in FIG.

In the above embodiment, the inverting amplifier circuit shown in FIG. 2 has been described, but generally, if the semiconductor resistor having the structure of FIG. 1 is used as the resistor for determining the amplification degree of the amplifier circuit, the amplification degree is the applied voltage. It is possible to obtain an amplifier circuit having good linearity, which can be maintained constant without depending on.

In the structure of FIG. 1, two resistance elements are formed, but in the case of three or more resistance elements, each well is formed and a resistance region is formed in each well. Each well is used as a floating structure. Also, it goes without saying that the same can be applied to one resistance element.

Further, it is obvious that the conductivity type of each part of the semiconductor device may be opposite to that of the above embodiment.

[0035]

As described above, according to the present invention, it is possible to eliminate the depletion layer by setting the impurity diffused resistance to a floating state in terms of potential, so that there is an effect that the voltage dependency of the resistance value is eliminated. .

If this semiconductor resistor having no voltage dependency is applied to the resistance element that determines the amplification factor of the amplifier circuit, the amplification factor has no voltage dependency, so that the amplifier circuit having good linearity can be obtained. It is a thing.

Further, it is obvious that the conductivity type of each part of the semiconductor device may be opposite to that of the above-mentioned embodiment.

[Brief description of drawings]

FIG. 1 is a sectional view of a semiconductor resistance device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of an inverting amplifier circuit to which the semiconductor resistance device of the present invention is applied.

FIG. 3 is a cross-sectional view of a conventional semiconductor resistance device.

FIG. 4 is a diagram with voltage dependence of the resistance device of FIG.

5 shows the input / output characteristics of the inverting amplifier circuit of FIG. 2 in comparison with a conventional example and the present invention.

FIG. 6 is a cross-sectional view of another conventional semiconductor resistance device.

[Explanation of symbols]

 1 signal source 2 input resistance 4 feedback resistance 7 operational amplifier 11 semiconductor substrate 12 and 14 impurity region (well) 13 and 15 resistance region

Claims (5)

[Claims] 1. A semiconductor substrate of a first conductivity type, an impurity region of a second conductivity type formed on one main surface of the semiconductor substrate, and a resistance region of a first conductivity type formed in the impurity region. And a semiconductor resistance device, wherein the impurity region is used in a state of being electrically released. 2. The first conductivity type is P-type, and the second conductivity type is P-type.
2. The semiconductor resistance device according to claim 1, wherein the conductivity type is N type, and the lowest potential of the circuit is applied to the semiconductor substrate. 3. The impurity region has first and second impurity regions, and first and second resistance regions, which are the resistance regions, are formed in each of the first and second impurity regions. 3. The semiconductor resistance device according to claim 1, wherein the first and second impurity regions are used in a state of being electrically released. 4. An amplifier circuit, wherein the semiconductor resistance device according to claim 1 is used as a resistance element for determining an amplification degree. 5. An amplifier circuit, wherein the first resistance region according to claim 3 is used as an input resistance of an operational amplifier, and the second resistance region is used as a feedback resistance of the operational amplifier.