JP2013134084A - Magnetic sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic sensor in which dispersion in detection sensitivity can be suppressed easily and various sensitivities can be selected even in one type of magnetic sensor.SOLUTION: A magnetic sensor comprises a magnetoresistance element section 60, a comparator 71, and first and second resistors 85 and 86 which are connected in series with each other. The magnetoresistance element section 60 outputs a potential difference constituted of a first voltage (voltage at a midpoint 66) and a second voltage (voltage at a midpoint 67) in accordance with a magnetic field to be applied. The comparator 71 includes a (+) input terminal to which the first voltage (voltage at the midpoint 66) is inputted, a (-) input terminal to which the second voltage (voltage at the midpoint 67) is inputted, an output terminal 82 which outputs a detection signal when the potential difference between the first voltage and the second voltage exceeds a threshold voltage, and a sensitivity regulation terminal 83 which regulates the threshold voltage. A voltage at a connecting point connecting the first resistor 85 and the second resistor 86 is applied to the sensitivity regulation terminal 83.

Description

  The present invention relates to a magnetic sensor that detects a magnetic field.

  An AMR (Anisotropic Magneto-Resistance) sensor using an anisotropic magnetoresistance effect is a sensor using the magnetoresistance effect of a ferromagnetic material. This magnetoresistive effect is a phenomenon in which the electrical resistance is changed by changing electrons in a direction that stabilizes and compensates for the distortion of the electron distribution accompanying the application of the magnetic field in terms of energy. In this type of magnetic sensor, the angle between the direction of the applied magnetic field and the current flowing through the magnetoresistive element is 90 °, and the direction of the applied magnetic field and the direction of current flowing through the magnetoresistive element are the same. By connecting a magnetoresistive element with a folded structure with an angle of 0 ° in series and connecting the connection point to the input of the comparator, the midpoint potential difference of the series resistance structure is identified, and this is amplified and magnetized. Is being detected.

  FIG. 7 is a circuit diagram showing a related art magnetic sensor. FIG. 8 is a plan view showing the shape of the magnetoresistive element portion in FIG. FIG. 9 is a graph showing the relationship between the applied magnetic field and the potential difference output from the magnetoresistive element in the magnetic sensor of FIG. Hereinafter, description will be given based on these drawings.

  FIG. 7 shows a basic circuit configuration of a related art magnetic sensor. In the magnetoresistive element unit 10, the magnetoresistive elements 11 to 14 form a bridge circuit. That is, the magnetoresistive element 11 and the magnetoresistive element 12 are connected to the power supply terminal 31 via the contact 15, and the magnetoresistive element 13 and the magnetoresistive element 14 are connected to the ground terminal 33 via the contact 18. A midpoint 16 that is a connection point between the magnetoresistive element 11 and the magnetoresistive element 14 is connected to the + input terminal of the comparator 21, and a midpoint 17 that is a connection point between the magnetoresistive element 12 and the magnetoresistive element 13 is The negative input terminal of the comparator 21 is connected.

  In the waveform processing unit 20, the comparator 21 and the positive feedback resistor 22 are arranged so as to have a comparison amplification function. The resistor 22 is connected between the output terminal 32 and the + input terminal of the comparator 21.

  FIG. 8 shows the shape of the magnetoresistive element unit 10. The magnetoresistive element 11 and the magnetoresistive element 13 have a folded structure in which a number of vertical lattices are connected to each other, and are formed as a thin film on an IC substrate. The magnetoresistive element 12 and the magnetoresistive element 14 have a folded structure in which a large number of lateral lattices are connected to each other, and are formed as a thin film on an IC substrate. The four magnetoresistive elements 11 to 14 having lattices in different directions are connected in series to form a bridge circuit. Here, the magnetoresistive element 11 and the magnetoresistive element 13 are resistors having a detection magnetic field of 90 °, and the magnetoresistive element 12 and the magnetoresistive element 14 are resistors having a detection magnetic field of 0 °.

  When a magnetic field is applied from the left direction of FIG. 8, the resistance values of the magnetoresistive element 11 and the magnetoresistive element 13 decrease due to the anisotropic magnetoresistive effect. As a result, the potential at the midpoint between the magnetoresistive element 11 and the magnetoresistive element 14 increases, and the potential at the midpoint 17 between the magnetoresistive element 12 and the magnetoresistive element 13 decreases.

  At this time, as shown in FIG. 9, the potential difference 42 between the midpoint 16 and the midpoint 17 with respect to the applied magnetic field changes. That is, the potential difference 42 increases toward the + side as the applied magnetic field increases, and when the potential difference 42 exceeds the threshold voltage 44 of the comparator 21, the detected magnetic field 46 is detected. Is output. Here, the magnetic field when the detection signal is output from the comparator 21 is referred to as a “detection magnetic field”.

  Thus, the magnetic field sensitivity to be detected is determined by the combination of the potential difference 42 between the midpoints 16 and 17 of the magnetoresistive elements 11 to 14 and the threshold voltage 44 of the comparator 21. On the other hand, during mass production, the potential difference 42 between the midpoints 16 and 17 varies from the potential difference 41 to the potential difference 43 due to slight differences in manufacturing processes and materials. As a result, the magnetic sensor is a product having a certain sensitivity variation range 48 because the detection magnetic field 46 varies from the detection magnetic field 45 to the detection magnetic field 47.

  Next, techniques disclosed in the following patent documents will be described.

  In patent document 1, the magnetic sensor sensitivity adjustment method of a banknote identification device is disclosed. This magnetic sensor sensitivity adjustment method creates a magnetic field around the magnetic sensor, measures the output of the resulting magnetic sensor, determines the sensitivity of the magnetic sensor based on the output and the strength of the magnetic field, and apparently displays the sensitivity. , To adjust to a predetermined level.

  Patent Document 2 discloses a position detection device. This position detection device is a device that detects a position by a permanent magnet provided on a moving object. The position detection device outputs a detection signal corresponding to the strength of the magnetic field, and a soft magnetism for reducing the strength of the magnetic field. It is composed of a body adjustment plate. And the sensitivity of a position detection apparatus is adjusted by adjusting the strength of a magnetic field with this adjustment board.

  Patent Document 3 discloses a magnetic detection device in which the operation is stabilized by providing hysteresis to the threshold voltage for detection.

JP 63-157082 A Japanese Patent Laid-Open No. 04-132901 Re-specialized WO2008 / 099662

National Semiconductor "LMP7300" data sheet, [Searched on December 20, 2011], Internet <URL: http://www.national.com/pf/LM/LMP7300.html>

  The first problem is that the sensitivity of related art magnetic sensors varies from one magnetic sensor to another. As described above, this is due to the following reason. The sensitivity of the magnetic sensor uses fluctuation due to application of a magnetic field of the potential difference at the midpoint constituted by a magnetoresistive element. For this reason, the resistance value of the magnetoresistive element always varies due to some manufacturing variation, and as a result, the potential difference at the midpoint varies. Therefore, the magnitude of the magnetic field to be detected varies within a certain range.

  The second problem is that the required sensitivity of the magnetic sensor differs depending on the method of use. Main applications of magnetic sensors include position detection and open / close detection combined with magnets. For example, in position detection, there are many different distances to detect, and the magnitude of the magnetic field to be detected varies depending on the positional relationship between the magnet and the magnetic sensor. It is necessary to prepare accordingly.

  In addition, the techniques disclosed in Patent Documents 1 and 2 have a problem in that the sensitivity of the magnetic sensor is adjusted by mechanical means, resulting in an increase in complexity and size. The technique disclosed in Patent Document 3 does not consider adjusting the sensitivity.

  Accordingly, an object of the present invention is to provide a magnetic sensor that can easily suppress variation in detection sensitivity and can select various sensitivities even with one type.

The magnetic sensor according to the present invention is:
A magnetoresistive element unit that outputs a potential difference composed of a first voltage and a second voltage in accordance with an applied magnetic field;
A comparator having a + input terminal for inputting the first voltage, a-input terminal for inputting the second voltage, and an output terminal for outputting a detection signal when the potential difference exceeds a threshold voltage;
In a magnetic sensor comprising
The comparator further includes a sensitivity adjustment terminal for adjusting the threshold voltage.
It is characterized by that.

  According to the present invention, since the sensitivity adjustment terminal for adjusting the threshold voltage is provided in the comparator, variations in detection sensitivity can be easily suppressed, and various sensitivities can be selected even with one type.

It is a circuit diagram which shows Embodiment 1 of the magnetic sensor which concerns on this invention. It is a top view which shows the shape of the magnetoresistive element part in FIG. 2 is a graph showing a relationship between a resistance value of a resistor connected to a sensitivity adjustment terminal and a magnetic field when a detection signal is output from a comparator in the magnetic sensor of FIG. 1. 2 is a graph showing a relationship between a resistance value of a resistor connected to a sensitivity adjustment terminal and a threshold voltage of a comparator in the magnetic sensor of FIG. 2 is a graph showing a relationship between an applied magnetic field and a potential difference output from a magnetoresistive element unit in the magnetic sensor of FIG. 1. It is a circuit diagram which shows Embodiment 2 of the magnetic sensor which concerns on this invention. It is a circuit diagram which shows the magnetic sensor of related technology. It is a top view which shows the shape of the magnetoresistive element part in FIG. It is a graph which shows the relationship between the magnetic field applied in the magnetic sensor of FIG. 7, and the electric potential difference output from a magnetoresistive element part.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as “embodiments”) will be described with reference to the accompanying drawings. In addition, since the shape drawn in drawing is drawn so that those skilled in the art can understand easily, it does not necessarily correspond with an actual dimension and ratio.

  FIG. 1 is a circuit diagram showing Embodiment 1 of a magnetic sensor according to the present invention. FIG. 2 is a plan view showing the shape of the magnetoresistive element portion in FIG. Hereinafter, description will be given based on these drawings.

  The magnetic sensor according to the first embodiment includes a magnetoresistive element unit 60, a comparator 71, and a first resistor 85 and a second resistor 86 that are connected in series with each other. The magnetoresistive element unit 60 outputs a potential difference composed of a first voltage (voltage at the midpoint 66) and a second voltage (voltage at the midpoint 67) according to the applied magnetic field. The comparator 71 has a + input terminal for inputting the first voltage (voltage at the midpoint 66), a − input terminal for inputting the second voltage (voltage at the midpoint 67), the first voltage, and the second voltage. When the potential difference from the voltage exceeds the threshold voltage, an output terminal 82 that outputs a detection signal and a sensitivity adjustment terminal 83 that adjusts the threshold voltage are provided. A voltage at a connection point that connects the first resistor 85 and the second resistor 86 is applied to the sensitivity adjustment terminal 83. The first and second resistors 85 and 86 may be variable types whose resistance values can be freely changed.

  The magnetoresistive element unit 60 includes a first magnetoresistive element 61 and a fourth magnetoresistive element 64 connected in series with each other, and a second magnetoresistive element 62 and a third magnetoresistive element 63 connected in series with each other. Have The first and third magnetoresistive elements 61 and 63 have a folded structure in which the angle formed between the applied magnetic field direction and the current flowing through the magnetoresistive elements 61 and 63 is 90 °. The second and fourth magnetoresistive elements 62 and 64 have a folded structure in which the angle formed between the applied magnetic field direction and the current flowing through the magnetoresistive elements 62 and 64 is 0 °. The first and second magnetoresistive elements 61 and 62 are connected to a power supply terminal 81 on the positive voltage side via a contact 65, and the third and fourth magnetoresistive elements 63 and 64 are connected to a negative voltage via a contact 68. It is connected to the ground terminal 84 which is the side. The first voltage is a voltage at a midpoint 66 that is a connection point connecting the first magnetoresistive element 61 and the fourth magnetoresistive element 64. The second voltage is a voltage at a midpoint 67 that is a connection point connecting the second magnetoresistive element 62 and the third magnetoresistive element 63.

  The comparator 71 has a hysteresis setting terminal for setting a threshold voltage hysteresis in advance. Such a comparator 71 is commercially available. For example, a trade name “LMP7300 (Micropower Precision Comparator and Precision Reference with Adjustable Hysteresis)” manufactured by National Semiconductor Corporation can be cited (see Non-Patent Document 1). . This hysteresis setting terminal has a rising voltage adjustment terminal that adjusts the rising voltage, which is a threshold voltage when the potential difference shifts from the low level to the high level, and a threshold value when the potential difference shifts from the high level to the low level. A falling voltage adjusting terminal for adjusting a falling voltage which is a voltage. In the first embodiment, as the sensitivity adjustment terminal 83, a rising voltage adjustment terminal among the hysteresis setting terminals is used. The rising voltage adjustment terminal can adjust the rising voltage in accordance with the applied voltage. Of course, instead of a commercially available comparator, a comparator having the same function may be designed and used.

  The positive feedback resistor 72 forms a waveform processing unit 70 together with the comparator 71, and is connected between the output terminal 82 and the + input terminal of the comparator 71. The operation of the resistor 72 will be described. The resistance values of the magnetoresistive elements 61 and 64 and the resistor 72 are R61, R64 and R72, respectively, the power supply voltage supplied from the power supply terminal 81 is VH, and the parallel resistance is indicated by “//”. Here, when the output terminal 82 of the comparator 71 is at L level, the voltage at the + input terminal of the comparator 71 is VH × R64 // R72 / (R61 + R64 // R72). When the output terminal 82 of the comparator 71 becomes H level, the voltage at the + input terminal of the comparator 71 increases as VH × R64 / (R64 + R61 // R72). Thereby, the resistor 72 sets the threshold voltage hysteresis of the comparator 71. That is, in the first embodiment, the rising voltage in the hysteresis of the threshold voltage set by the resistor 72 is further adjusted by the sensitivity adjustment terminal 83.

  Next, the magnetic sensor of Embodiment 1 will be described in more detail.

  As shown in FIG. 1, the magnetic sensor according to the first embodiment includes a magnetoresistive element unit 60 and a waveform processing unit 70 formed of an IC (Integrated Circuit). The magnetoresistive element unit 60 has a resistance bridge structure, and the midpoints 66 and 67 of the resistance connection are connected to the input terminal of the comparator 71 of the waveform processing unit 70. The waveform processing unit 70 includes a comparator 71 and a positive feedback resistor 22, and is provided with a power supply terminal 81, an output terminal 82, a sensitivity adjustment terminal 83, and a ground terminal 84.

  As shown in FIG. 2, the magnetoresistive element unit 60 includes magnetoresistive elements 61 to 64. The magnetoresistive element 61 and the magnetoresistive element 63 have the same direction of the reacting magnetic field and have a continuously repeating structure. Similarly, the magnetoresistive element 62 and the magnetoresistive element 64 have the same direction of the reacting magnetic field and have a continuously repeating structure. However, the direction of the magnetic field to which the magnetoresistive elements 61 and 63 react is different from the direction of the magnetic field to which the magnetoresistive elements 62 and 64 react by 90 °.

  The first embodiment uses a magnetic sensor in which anisotropic magnetoresistive elements 61 to 64 are formed on an IC by providing a sensitivity adjustment terminal 83 that can adjust the threshold voltage of the comparator 71. Provided is a magnetic sensor with a sensitivity adjustment function that can be easily set to an arbitrary sensitivity on the side to be used in accordance with the intended use and the conditions to be used.

  3 shows the resistance values of the resistors 85 and 86 connected to the sensitivity adjustment terminal 83 and the magnetic field when the detection signal is outputted from the comparator 71 (hereinafter referred to as “detection magnetic field”) in the magnetic sensor of FIG. It is a graph which shows the relationship. Hereinafter, a description will be given based on FIGS. 1 and 3.

  As shown in FIG. 3, the detection magnetic field 92 when the resistors 85 and 86 are not connected to the sensitivity adjustment terminal 83 is naturally constant regardless of the resistance values of the resistors 85 and 86. On the other hand, the detection magnetic field 91 when the resistor 85 is connected between the sensitivity adjustment terminal 83 and the power supply terminal is larger than the detection magnetic field 92, and becomes larger as the resistance value of the resistor 85 is smaller. In addition, the detection magnetic field 93 when the resistor 86 is connected between the sensitivity adjustment terminal 83 and the ground terminal is smaller than the detection magnetic field 92, and becomes smaller as the resistance value of the resistor 86 is smaller.

  4 is a graph showing the relationship between the resistance values of the resistors 85 and 86 connected to the sensitivity adjustment terminal 83 and the threshold voltage (threshold voltage) of the comparator 71 in the magnetic sensor of FIG. Hereinafter, description will be given based on FIG. 1 and FIG.

  As shown in FIG. 4, the threshold voltage 202 when the resistors 85 and 86 are not connected to the sensitivity adjustment terminal 83 is, of course, constant regardless of the resistance values of the resistors 85 and 86. . On the other hand, the threshold voltage 201 when the resistor 85 is connected between the sensitivity adjustment terminal 83 and the power supply terminal is larger than the threshold voltage 202, and further increases as the resistance value of the resistor 85 decreases. . Further, the threshold voltage 203 when the resistor 86 is connected between the sensitivity adjustment terminal 83 and the ground terminal is smaller than the threshold voltage 202, and becomes smaller as the resistance value of the resistor 86 is smaller. .

  FIG. 5 is a graph showing the relationship between the applied magnetic field and the potential difference 204 output from the magnetoresistive element unit 60 in the magnetic sensor of FIG. Hereinafter, a description will be given based on FIGS. 1 and 5.

  When a magnetic field intersecting with the magnetoresistive elements 61 and 63 at 90 ° is applied, the resistance value of the magnetoresistive elements 61 and 63 decreases due to the anisotropic magnetoresistive effect. Accordingly, the potential at the midpoint 66 increases and the potential at the midpoint 67 decreases. As a result, the potential difference 204 between the potential at the midpoint 66 and the potential at the midpoint 67 increases as the applied magnetic field increases.

  When the resistors 85 and 86 are not connected to the sensitivity adjustment terminal 83, the detected magnetic field 206 is where the potential difference 204 exceeds the threshold voltage 202 of the comparator 71. On the other hand, when the resistor 85 is connected between the sensitivity adjustment terminal 83 and the power supply terminal, the threshold voltage 201 changes to the + side of the threshold voltage 202 when the resistance value of the resistor 85 is sufficiently reduced. To do. Therefore, when the potential difference 204 exceeds the threshold voltage 201 becomes the detection magnetic field 207, the detection magnetic field 207 becomes larger than the detection magnetic field 206. Further, when the resistor 86 is connected between the sensitivity adjustment terminal 83 and the ground terminal, the threshold voltage 203 changes to the minus side of the threshold voltage 202 when the resistance value of the resistor 86 is sufficiently reduced. To do. Therefore, when the potential difference 204 exceeds the threshold voltage 203 becomes the detection magnetic field 205, the detection magnetic field 205 becomes smaller than the detection magnetic field 206. In this way, it is possible to adjust to an arbitrary detection magnetic field.

  According to the magnetic sensor of the first embodiment, the circuit configuration and magnetoresistive element shape shown in FIGS. 1 and 2 are adopted, and the function of adjusting the threshold voltage by the resistance value connected to the comparator shown in FIG. 4 is given. The function of adjusting the detection magnetic field as shown in FIG. 3 is realized from the relationship between the potential difference at the midpoint and the threshold voltage of the comparator shown in FIG. In other words, in the first embodiment, a terminal having a function capable of arbitrarily adjusting the threshold voltage according to the resistance value of the resistor connected to the comparator is added, and between the terminal and the power supply or between the terminal and the ground. Arbitrary sensitivity adjustment is made possible by the resistance value of the resistor connected to.

  Next, the effect of the first embodiment will be described.

  The first effect is that the side on which the magnetic sensor is used can arbitrarily adjust the sensitivity of the magnetic sensor, so that, for example, it is easy to determine the conditions for arranging the magnet and the magnetic sensor. The reason is as follows. When position detection or open / close detection is performed using a combination of a magnetic sensor and a magnet, the sensitivity of the magnetic sensor required differs depending on the structure. This is because the sensitivity of the magnetic sensor can be arbitrarily adjusted, so that the sensitivity of the magnetic sensor can be set regardless of the structure.

  The second effect is that detection setting under a predetermined condition becomes easy in the use of position detection and open / close detection. The reason is that a magnet and a magnetic sensor are arranged at a position where they are actually used, and the sensitivity can be adjusted while being adjusted so as to detect at a predetermined position.

  That is, according to the first embodiment, the sensitivity adjustment terminal for adjusting the threshold voltage is provided in the comparator, so that variations in detection sensitivity can be easily suppressed and various sensitivities can be selected even with one type. .

  FIG. 6 is a circuit diagram showing Embodiment 2 of the magnetic sensor according to the present invention. Hereinafter, a description will be given based on FIGS. 1 and 6.

  Magnetoresistive element unit 110, magnetoresistive elements 111, 112, 113, 114, contacts 115, 118, midpoints 116, 117, waveform processing unit 120, comparator 121, positive feedback resistor in the magnetic sensor of the second embodiment 122, the power supply terminal 131, the output terminal 132, the sensitivity adjustment terminal 133, and the ground terminal 134 are the magnetoresistive element unit 60, the magnetoresistive elements 61, 62, 63, and 64, and the contacts 65 and 68, respectively, in the magnetic sensor of the first embodiment. Midpoints 66 and 67, waveform processing unit 70, comparator 71, positive feedback resistor 72, power supply terminal 81, output terminal 82, sensitivity adjustment terminal 83, and ground terminal 84 are the same.

  However, in the first embodiment, the voltage at the midpoint between the resistors 85 and 86 is applied to the sensitivity adjustment terminal 83. On the other hand, in the second embodiment, a predetermined voltage is applied to the sensitivity adjustment terminal 133 by the DC voltage power supply 135. The second embodiment differs from the first embodiment in this point, but has the same operations and effects as the first embodiment. That is, according to the second embodiment, the threshold voltage of the comparator 121 can be adjusted by applying an arbitrary voltage to the sensitivity adjustment terminal 133 by the DC voltage power supply 135, so that the detected magnetic field can be adjusted. Note that the DC voltage power supply 135 may be a variable type that can freely change the output voltage.

  Although the present invention has been described with reference to the above embodiments, the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention. Further, the present invention includes a combination of some or all of the configurations of the above-described embodiments as appropriate.

  Although a part or all of the above embodiments can be described as the following supplementary notes, the present invention is not limited to the following configurations.

[Appendix 1] A magnetoresistive element unit that outputs a potential difference composed of a first voltage and a second voltage in accordance with an applied magnetic field;
A comparator having a + input terminal for inputting the first voltage, a-input terminal for inputting the second voltage, and an output terminal for outputting a detection signal when the potential difference exceeds a threshold voltage;
In a magnetic sensor comprising
The comparator further includes a sensitivity adjustment terminal for adjusting the threshold voltage.
Magnetic sensor characterized by the above.

[Appendix 2] A magnetic sensor as set forth in Appendix 1,
The magnetoresistive element portion includes first and fourth magnetoresistive elements connected in series with each other and second and third magnetoresistive elements connected in series with each other,
The first and third magnetoresistive elements have a folded structure in which an angle formed between a direction of a magnetic field applied and a current flowing through the magnetoresistive element is 90 °.
The second and fourth magnetoresistive elements have a folded structure in which an angle formed between an applied magnetic field direction and a current flowing through the magnetoresistive element is 0 °,
The first and second magnetoresistive elements are connected to the + voltage side,
The third and fourth magnetoresistive elements are connected to a negative voltage side, and the first voltage is a voltage at a connection point connecting the first magnetoresistive element and the fourth magnetoresistive element. ,
The second voltage is a voltage at a connection point connecting the second magnetoresistive element and the third magnetoresistive element.
Magnetic sensor characterized by the above.

[Appendix 3] The magnetic sensor according to Appendix 1 or 2,
The comparator has a hysteresis setting terminal for setting the hysteresis of the threshold voltage in advance,
The sensitivity adjustment terminal uses the hysteresis setting terminal.
Magnetic sensor characterized by the above.

[Appendix 4] A magnetic sensor as set forth in Appendix 3,
The hysteresis setting terminal includes a rising voltage adjusting terminal that adjusts a rising voltage that is the threshold voltage when the potential difference shifts from a low level to a high level, and a hysteresis voltage when the potential difference shifts from a high level to a low level. A falling voltage adjustment terminal for adjusting the falling voltage which is the threshold voltage,
Magnetic sensor characterized by the above.

[Appendix 5] A magnetic sensor as set forth in Appendix 4,
The rising voltage adjustment terminal is capable of adjusting the rising voltage according to an applied voltage.
Magnetic sensor characterized by the above.

[Appendix 6] A magnetic sensor as set forth in Appendix 5,
A first resistor and a second resistor connected in series with each other;
A voltage at a connection point connecting the first resistor and the second resistor is applied to the rising voltage adjustment terminal,
Magnetic sensor characterized by the above.

[Appendix 7] A magnetic sensor as set forth in Appendix 5,
A predetermined voltage is applied to the rising voltage adjustment terminal,
Magnetic sensor characterized by the above.

[Appendix 11] A magnetic sensor using a magnetoresistive element whose resistance value changes when a magnetic field is applied,
When four magnetoresistive elements having at least one resistance value different from the remaining resistance values are connected in a bridge shape through four connection points and a power supply voltage is applied to the two opposite connection points, the other two opposite resistance values are connected. A magnetoresistive element that outputs a midpoint potential difference from two connection points;
A circuit having a comparison amplification function comprising a comparator having a detection level set higher than a level based on a midpoint potential difference voltage from the magnetoresistive element portion and a feedback resistor;
A magnetic sensor characterized in that a magnetic field intensity to be detected can be adjusted by having a terminal capable of arbitrarily adjusting the detection level by a resistance value of an external resistor connected externally.

[Appendix 12] A magnetic sensor as set forth in Appendix 11,
The external resistance connected to the magnetic sensor is connected between a power supply or a ground, and the magnitude of the magnetic field to be detected can be adjusted to be larger or smaller than when the external resistance is not connected. Magnetic sensor.

  As an application example of the present invention, for example, there is a magnetic sensor that detects a magnetic field by being incorporated in an apparatus for detecting rotation or position of an object.

DESCRIPTION OF SYMBOLS 10 Magnetoresistive element part 11, 12, 13, 14 Magnetoresistive element 15, 18 Contact 16, 16 Middle point 20 Waveform processing part 21 Comparator 22 Resistor for positive feedback 31 Power supply terminal 32 Output terminal 33 Ground terminal 41, 42, 43 Potential difference at midpoint of magnetoresistive element bridge 44 Comparator threshold voltage 45, 46, 47 Detection magnetic field 48 Sensitivity variation range

60 Magnetoresistive Element 61, 62, 63, 64 Magnetoresistive Element 65, 68 Contact 66, 67 Middle Point 70 Waveform Processing Unit 71 Comparator 72 Positive Feedback Resistor 81 Power Supply Terminal 82 Output Terminal 83 Sensitivity Adjustment Terminal 84 Ground Terminal 85, 86 Resistor 91, 92, 93 Detection magnetic field

DESCRIPTION OF SYMBOLS 110 Magnetoresistance element part 111,112,113,114 Magnetoresistance element 115,118 Contact 116,117 Midpoint 120 Waveform processing part 121 Comparator 122 Resistor for positive feedback 131 Power supply terminal 132 Output terminal 133 Sensitivity adjustment terminal 134 Ground terminal 135 DC voltage power supply

201, 202, 203 Threshold voltage 204 Potential difference at midpoint of magnetoresistive element bridge 205, 206, 207 Detection magnetic field

Claims (7)

A magnetoresistive element unit that outputs a potential difference composed of a first voltage and a second voltage in accordance with an applied magnetic field;
A comparator having a + input terminal for inputting the first voltage, a-input terminal for inputting the second voltage, and an output terminal for outputting a detection signal when the potential difference exceeds a threshold voltage;
In a magnetic sensor comprising
The comparator further includes a sensitivity adjustment terminal for adjusting the threshold voltage.
Magnetic sensor characterized by the above. The magnetic sensor according to claim 1,
The magnetoresistive element portion includes first and fourth magnetoresistive elements connected in series with each other and second and third magnetoresistive elements connected in series with each other,
The first and third magnetoresistive elements have a folded structure in which an angle formed between a direction of a magnetic field applied and a current flowing through the magnetoresistive element is 90 °.
The second and fourth magnetoresistive elements have a folded structure in which an angle formed between an applied magnetic field direction and a current flowing through the magnetoresistive element is 0 °,
The first and second magnetoresistive elements are connected to the + voltage side,
The third and fourth magnetoresistive elements are connected to a negative voltage side, and the first voltage is a voltage at a connection point connecting the first magnetoresistive element and the fourth magnetoresistive element. ,
The second voltage is a voltage at a connection point connecting the second magnetoresistive element and the third magnetoresistive element.
Magnetic sensor characterized by the above. The magnetic sensor according to claim 1 or 2,
The comparator has a hysteresis setting terminal for setting the hysteresis of the threshold voltage in advance,
The sensitivity adjustment terminal uses the hysteresis setting terminal.
Magnetic sensor characterized by the above. The magnetic sensor according to claim 3,
The hysteresis setting terminal includes a rising voltage adjusting terminal that adjusts a rising voltage that is the threshold voltage when the potential difference shifts from a low level to a high level, and a hysteresis voltage when the potential difference shifts from a high level to a low level. A falling voltage adjustment terminal for adjusting the falling voltage which is the threshold voltage,
Magnetic sensor characterized by the above. The magnetic sensor according to claim 4,
The rising voltage adjustment terminal is capable of adjusting the rising voltage according to an applied voltage.
Magnetic sensor characterized by the above. The magnetic sensor according to claim 5,
A first resistor and a second resistor connected in series with each other;
A voltage at a connection point connecting the first resistor and the second resistor is applied to the rising voltage adjustment terminal,
Magnetic sensor characterized by the above. The magnetic sensor according to claim 5,
A predetermined voltage is applied to the rising voltage adjustment terminal,
Magnetic sensor characterized by the above.

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