JP2016121944A - Magnetoresistance element circuit and bridge circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetoresistance element circuit with which it is possible to reduce the effect of a disturbance magnetic field and a bridge circuit using the same.SOLUTION: A magnetoresistance element circuit 5A includes four GMR elements 11-14 connected in series between a high power supply terminal T1a and a first middle point terminal T2a. The GMR elements 11-14 are disposed so that, when the magnetization direction P of a pin layer of, for example, the GMR element 11 is assumed to be a point of reference, the magnetization direction P of a pin layer of the GMR element 12, the magnetization direction P of a pin layer of the GMR element 13, and the magnetization direction P of a pin layer of the GMR element 14 are shifted by about 90 degrees each. The magnetoresistance element circuit 5A further includes a coil 31 magnetically coupled with the GMR element 11, a coil 33 magnetically coupled with the GMR element 12, a coil 35 magnetically coupled with the GMR element 13, and a coil 37 magnetically coupled with the GMR element 14.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a magnetoresistive element circuit and a bridge circuit using the same.

  For example, Patent Document 1 discloses a magnetically coupled isolator. This isolator includes an input circuit including a coil and a bridge circuit using four magnetoresistive elements, and the input circuit and the bridge circuit are electrically insulated. In the input circuit, a current corresponding to the input signal is supplied to the coil, and in the bridge circuit, a change in the magnetic field generated from the coil is detected using a magnetoresistive element.

JP-T-2001-521160

  However, in the prior art including Patent Document 1, when the magnetoresistive element is affected by a disturbance magnetic field, the output of the bridge circuit fluctuates. The present invention has been made in view of such circumstances, and one of the problems to be solved is to provide a magnetoresistive element circuit capable of reducing the influence of a disturbance magnetic field and a bridge circuit using the same. To do.

  In order to solve the above problems, a magnetoresistive element circuit according to an aspect of the present invention includes four GMR elements connected in series between a first terminal and a second terminal, and the four GMR elements are connected to each other. , The first GMR element, the second GMR element, the third GMR element, and the fourth GMR element, the second GMR element is based on the magnetization direction of the pinned layer of the first GMR element. The first to fourth directions so that the magnetization direction of the pinned layer of the element, the magnetization direction of the pinned layer of the third GMR element, and the magnetization direction of the pinned layer of the fourth GMR element are shifted by approximately 90 degrees. A GMR element is disposed, a first coil magnetically coupled to the first GMR element, a second coil magnetically coupled to the second GMR element, and a third magnetically coupled to the third GMR element And a fourth magnetically coupled to the fourth GMR element. Of and a coil, characterized in that.

  According to this aspect, the four GMR elements connected in series are arranged such that the magnetization direction of the pinned layer is shifted by approximately 90 degrees. The amount of change in the resistance value of each GMR element is determined by the angle between the magnetization direction of the pinned layer and the magnetization direction of the free layer. The direction of the disturbance magnetic field is constant for each GMR element, while the magnetization direction of the pinned layer is shifted by approximately 90 degrees. Therefore, the influence of the disturbance magnetic field can be reduced from the combined resistance value of the four GMR elements connected in series. For example, when there is a disturbance magnetic field and a current corresponding to an input signal is not supplied to each coil, the combined resistance values of the four GMR elements are constant. When there is a disturbance magnetic field and a current corresponding to an input signal is supplied to each coil, the combined resistance value of the four GMR elements changes the resistance value due to the disturbance magnetic field and the magnetic field generated from each coil. It becomes a value according to. Therefore, it is also possible to reduce the influence of the disturbance magnetic field by detecting the magnetic field generated from the coil using both.

  In the magnetoresistive element circuit described above, the magnetization direction of the pinned layer of the first GMR element, the direction of the magnetic field generated from the first coil, the magnetization direction of the pinned layer of the second GMR element, The direction of the magnetic field generated from the second coil, the magnetization direction of the pinned layer of the third GMR element and the direction of the magnetic field generated from the third coil, and the magnetization direction of the pinned layer of the fourth GMR element It is preferable that the first to fourth coils are arranged so that the directions of the magnetic fields generated from the fourth coil and the fourth coil are substantially the same (second mode).

  In the magnetoresistive element circuit described above, the magnetization direction of the pinned layer of the first GMR element, the direction of the magnetic field generated from the first coil, the magnetization direction of the pinned layer of the second GMR element, The direction of the magnetic field generated from the second coil, the magnetization direction of the pinned layer of the third GMR element and the direction of the magnetic field generated from the third coil, and the magnetization direction of the pinned layer of the fourth GMR element It is preferable that the first to fourth coils are arranged so that the directions of the magnetic fields generated from the fourth coil are substantially reversed (third mode).

  According to the second or third aspect, in each of the four GMR elements, the magnetization direction of the pinned layer of the GMR element and the direction of the magnetic field generated from the coil are substantially the same or substantially opposite. The detection sensitivity of the element circuit can be increased.

  A bridge circuit according to one embodiment of the present invention includes a first power supply terminal to which a first power supply potential is supplied, a second power supply terminal to which a second power supply potential is supplied, a midpoint terminal, and the first power supply. A first magnetoresistive element circuit provided between a terminal and the midpoint terminal; and a second magnetoresistive element circuit provided between the midpoint terminal and the second power supply terminal; The first magnetoresistive element circuit is the magnetoresistive element circuit described as the second aspect described above, and the second magnetoresistive element circuit is the magnetoresistive element circuit described as the third aspect. It is characterized by that.

  Also in this aspect, in each of the first and second magnetoresistive element circuits, the four GMR elements connected in series are arranged so that the magnetization direction of the pinned layer is shifted by approximately 90 degrees. The influence of the disturbance magnetic field can be reduced from the combined resistance value of the individual GMR elements. For example, when there is a disturbance magnetic field and a current corresponding to an input signal is supplied to each coil, the combined resistance value of four GMR elements in the first magnetoresistive element circuit and the second magnetoresistive element The combined resistance value of the four GMR elements in the circuit is a value corresponding to the change in resistance value due to the disturbance magnetic field and the magnetic field generated from each coil. However, in the first magnetoresistive element circuit, the magnetization direction of the pinned layer of the GMR element and the direction of the magnetic field generated from the coil are substantially the same, whereas in the second magnetoresistive element circuit, both directions are substantially the same. Since the reverse is true, the combined resistance value of the first magnetoresistive element circuit <the combined resistance value of the second magnetoresistive element circuit. Therefore, it is possible to reduce the influence of the disturbance magnetic field by detecting the magnetic field generated from the coil using the potential of the midpoint terminal when current is supplied to each coil.

  A bridge circuit according to one embodiment of the present invention includes a high power supply terminal to which a high power supply potential is supplied, a low power supply terminal to which a low power supply potential is supplied, a first midpoint terminal, and a second midpoint terminal. A first magnetoresistive element circuit provided between the high power supply terminal and the first midpoint terminal, and a second magnetism provided between the first midpoint terminal and the low power supply terminal. A resistor element circuit, the second magnetoresistive element circuit provided between the high power supply terminal and the second midpoint terminal, and provided between the second midpoint terminal and the low power supply terminal. And the first magnetoresistive element circuit is the magnetoresistive element circuit described as the second aspect described above, and the second magnetoresistive element circuit is the same as described above. It is the magnetoresistive element circuit described as the third aspect.

  Also in this aspect, in each of the first and second magnetoresistive element circuits, the four GMR elements connected in series are arranged so that the magnetization direction of the pinned layer is shifted by approximately 90 degrees. The influence of the disturbance magnetic field can be reduced from the combined resistance value of the individual GMR elements. For example, when there is a disturbance magnetic field and a current corresponding to an input signal is supplied to each coil, the combined resistance value of four GMR elements in the first magnetoresistive element circuit and the second magnetoresistive element The combined resistance value of the four GMR elements in the circuit is a value corresponding to a change in the resistance value due to the disturbance magnetic field and the magnetic field generated from each coil. Further, depending on whether the magnetization direction of the pinned layer of the GMR element and the direction of the magnetic field generated from the coil are substantially the same or substantially opposite, the combined resistance value of the first magnetoresistive element circuit <the second magnetism This is the combined resistance value of the resistive element circuit. Therefore, it is possible to reduce the influence of the disturbance magnetic field by detecting the magnetic field generated from the coil using the potentials of the first and second midpoint terminals when current is supplied to each coil.

It is a figure which shows the structural example of the bridge circuit which concerns on embodiment of this invention. It is a circuit diagram of a bridge circuit. It is a top view which shows the circuit layout in the 3A part of FIG. It is a circuit diagram which shows the equivalent circuit of a bridge circuit. It is a figure for demonstrating the influence which a disturbance magnetic field exerts on one GMR element. It is a figure which shows the synthetic magnetic field of an input signal magnetic field and a disturbance magnetic field. It is a figure for demonstrating the influence which a disturbance magnetic field exerts on a magnetoresistive element circuit.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<1. Embodiment>
FIG. 1 is a diagram illustrating a configuration example of a bridge circuit 1 according to an embodiment of the present invention.
The bridge circuit 1 is provided at the peripheral portion of the IC chip 3, and includes a high power supply terminal T1a to which a high power supply potential is supplied, a low power supply terminal T1b to which a low power supply potential is supplied, and a first middle point potential that is taken out. A midpoint terminal T2a and a second midpoint terminal T2b for taking out a second midpoint potential are provided. Four GMR (Giant Magneto Resistive Effect) elements 11 to 14 are connected in series on the path A from the high power terminal T1a to the first midpoint terminal T2a, and from the first midpoint terminal T2a to the low power terminal. Four GMR elements 15 to 18 are connected in series to the path D leading to T1b. Further, four GMR elements 21 to 24 are connected in series to a path B from the high power supply terminal T1a to the second midpoint terminal T2b, and a path from the second midpoint terminal T2b to the low power supply terminal T1b. Four GMR elements 25 to 28 are connected to C in series.

  The GMR element is a device that uses the giant magnetoresistive effect, and is formed, for example, by connecting a plurality of strip-shaped elements including a free layer, a spacer layer, a pinned layer, and a gap layer with lead wires. The magnetization direction P of the pinned layer is determined by a thermal ordering process. For example, as shown in the figure, the magnetization direction P of the pinned layer of each of the GMR elements 11 to 18 and 21 to 28 is perpendicular to the longitudinal direction of the element. In addition, the IC chip 3 can be fixed in a direction from the inside to the outside. Note that the magnetization direction P of the pinned layer may be opposite to that in FIG. 1 (the direction from the outside to the inside of the IC chip 3). Moreover, the white arrow shown in FIG. 1 is the initial magnetization direction of the free layer.

  In FIG. 1, eight coils 31 to 38 that generate an input signal magnetic field Hi are provided inside the path D of the IC chip 3. For example, the coil 31 is magnetically coupled to the GMR elements 11 and 28 and generates an input signal magnetic field Hi applied to the GMR elements 11 and 28. The coil 32 is magnetically coupled to the GMR elements 18 and 21 and generates an input signal magnetic field Hi applied to the GMR elements 18 and 21. The direction of the input signal magnetic field Hi generated from the coils 31, 33, 35, and 37 is the same as the magnetization direction P of the pinned layers of the GMR elements 11-14 and 25-28 that are magnetically coupled. On the other hand, the direction of the input signal magnetic field Hi generated from the coils 32, 34, 36, and 38 is opposite to the magnetization direction P of the pinned layers of the GMR elements 15-18 and 21-24 that are magnetically coupled. In FIG. 1, the coils 31 to 38 are illustrated inside the path D. However, as is apparent from the description of FIG. 3, each of the coils 31 to 38 is actually electromagnetically coupled. It is provided below the GMR element.

FIG. 2 is a circuit diagram of the bridge circuit 1 shown in FIG.
A high power supply potential VDD is supplied to the high power supply terminal T1a, and a low power supply potential VSS is supplied to the low power supply terminal T1b. A first midpoint potential V1 is taken out from the first midpoint terminal T2a, and a second midpoint potential V2 is taken out from the second midpoint terminal T2b. A magnetoresistive element circuit 5A is provided between the high power supply terminal T1a and the first midpoint terminal T2a, and a magnetoresistive element circuit 6A is provided between the first midpoint terminal T2a and the low power supply terminal T1b. Yes. A magnetoresistive element circuit 6B is provided between the high power supply terminal T1a and the second midpoint terminal T2b, and a magnetoresistive element circuit 5B is provided between the second midpoint terminal T2b and the low power supply terminal T1b. It has been. The magnetoresistive element circuits 5A and 6A are connected in series with the first midpoint terminal T2a interposed therebetween to form a half bridge circuit. In addition, the magnetoresistive element circuits 6B and 5B are connected in series with the second midpoint terminal T2b interposed therebetween, and constitute a half bridge circuit. Both half bridge circuits are connected in parallel to form a full bridge circuit (bridge circuit 1).

  The magnetoresistive element circuit 5 </ b> A includes four GMR elements 11 to 14 connected to the path A in FIG. 1 and four coils 31, 33, 35, and 37. As shown in FIG. 1 and FIG. 2, the four GMR elements 11 to 14 connected in series have, for example, the pin layer of the GMR element 12 when the magnetization direction P of the pin layer of the GMR element 11 is used as a reference. The magnetization direction P, the magnetization direction P of the pinned layer of the GMR element 13, and the magnetization direction P of the pinned layer of the GMR element 14 are shifted by 90 degrees. As described above, the GMR elements 11 to 14 are arranged one by one on the four peripheral edges of the IC chip 3 so that the magnetization direction P of the pinned layer is shifted by 90 degrees.

  Further, as shown in FIGS. 1 and 2, in the magnetoresistive element circuit 5A, the magnetization direction P of the pin layer of the GMR element 11, the direction of the input signal magnetic field Hi generated from the coil 31, and the magnetization of the pin layer of the GMR element 12 The direction P and the direction of the input signal magnetic field Hi generated from the coil 33, the magnetization direction P of the pinned layer of the GMR element 13 and the direction of the input signal magnetic field Hi generated from the coil 35, and the magnetization direction P of the pinned layer of the GMR element 14 The direction of the input signal magnetic field Hi generated from the coil 37 is the same. In this way, each of the coils 31, 33, 35, and 37 is arranged such that the direction of the input signal magnetic field Hi is the same as the magnetization direction P of the pinned layer of the GMR element that is magnetically coupled.

  The magnetoresistive element circuit 5B has the same configuration as the magnetoresistive element circuit 5A. That is, the magnetoresistive element circuit 5 </ b> B includes four GMR elements 25 to 28 connected to the path C in FIG. 1 and four coils 31, 33, 35, and 37. The GMR elements 25 to 28 are arranged on the four peripheral edges of the IC chip 3 so that the magnetization direction P of the pinned layer is shifted by 90 degrees. Each of the coils 31, 33, 35, and 37 is arranged so that the direction of the input signal magnetic field Hi is the same as the magnetization direction P of the pinned layer of the GMR element that is magnetically coupled.

  The magnetoresistive element circuit 6 </ b> A includes four GMR elements 15 to 18 connected to the path D in FIG. 1 and four coils 32, 34, 36 and 38. Also in the magnetoresistive element circuit 6A, the GMR elements 15 to 18 are arranged one by one on the four peripheral edges of the IC chip 3 so that the magnetization direction P of the pinned layer is shifted by 90 degrees. Further, in the magnetoresistive element circuit 6A, the magnetization direction P of the pinned layer of the GMR element 15 and the direction of the input signal magnetic field Hi generated from the coil 38, the magnetization direction P of the pinned layer of the GMR element 16 and the input generated from the coil 36. The direction of the signal magnetic field Hi, the magnetization direction P of the pinned layer of the GMR element 17 and the direction of the input signal magnetic field Hi generated from the coil 34, and the direction of magnetization of the pinned layer of the GMR element 18 and the input signal magnetic field Hi generated from the coil 32. The direction of is opposite. Thus, each of the coils 32, 34, 36, and 38 is arranged so that the direction of the input signal magnetic field Hi is opposite to the magnetization direction P of the pinned layer of the GMR element that is magnetically coupled.

  The magnetoresistive element circuit 6B has the same configuration as the magnetoresistive element circuit 6A. That is, the magnetoresistive element circuit 6B includes four GMR elements 21 to 24 and four coils 32, 34, 36, and 38 connected to the path B in FIG. The GMR elements 21 to 24 are arranged at the four peripheral edges of the IC chip 3 so that the magnetization direction P of the pinned layer is shifted by 90 degrees. Each of the coils 32, 34, 36, and 38 is arranged so that the direction of the input signal magnetic field Hi is opposite to the magnetization direction P of the pinned layer of the GMR element that is magnetically coupled. All the GMR elements 11 to 18 and 21 to 28 in the bridge circuit 1 preferably have the same electrical characteristics. It is preferable that all the coils 31 to 38 in the bridge circuit 1 have the same electrical characteristics.

FIG. 3 is a plan view showing a circuit layout in the section 3A of FIG.
The wiring pattern 40 (black) is a wiring for connecting the GMR elements 12, 17, 22, and 27. As is apparent from the figure, each GMR element shown in FIGS. 1 and 2 is actually three GMR elements connected in series. For example, the GMR element 12 in FIG. 1 corresponds to the three GMR elements 12A, 12B, and 12C in FIG. The GMR element 27 in FIG. 1 corresponds to the three GMR elements 27A, 27B, and 27C in FIG.

  The wiring pattern 41 (gray) is a coil pattern formed in a spiral shape, and corresponds to the coils 33 and 34 shown in FIGS. In the spiral wiring pattern 41, the direction of the current flowing on the wiring pattern 41 extending in the vertical direction is reversed between the left side and the right side of the center. Accordingly, the GMR elements 12A to 12C and 27A to 27C are formed on the wiring pattern 41 extending in the vertical direction on the left side in the drawing, and the GMR elements 17A to 17C are formed on the wiring pattern 41 extending in the vertical direction on the right side in the drawing. And 22A to 22C, two coils 33 and 34 in which the direction of the input signal magnetic field Hi is reversed can be formed by one spiral wiring pattern 41. 3 is an out-side wiring pattern for the coils 33 and 34, and is formed in a layer different from the in-side wiring pattern 41. In FIG.

FIG. 4 is a circuit diagram showing an equivalent circuit of the bridge circuit 1.
In the figure, the resistance value of the magnetoresistive element circuit 5A (the combined resistance value of the GMR elements 11 to 14) is represented as Ra, and the resistance value of the magnetoresistive element circuit 6A (the combined resistance value of the GMR elements 15 to 18) is represented as Rb. Represents. Further, the resistance value of the magnetoresistive element circuit 6B (the combined resistance value of the GMR elements 21 to 24) is represented as Rc, and the resistance value of the magnetoresistive element circuit 5B (the combined resistance value of the GMR elements 25 to 28) is represented as Rd. Yes. A comparator 50 is provided in the subsequent stage of the bridge circuit 1, the first midpoint terminal T2a of the bridge circuit 1 is connected to the first input terminal (−) of the comparator 50, and the second midpoint terminal T2b of the bridge circuit 1 is Are connected to the second input terminal (+) of the comparator 50. As a result, the output voltage of the bridge circuit 1 is amplified by the comparator 50 with a predetermined amplification factor (gain) and output from the comparator 50 as the output signal Vout. Since the bridge circuit 1 is a full bridge circuit as described above, the signal level of the output signal Vout can be doubled compared to the case of the half bridge circuit, and the detection sensitivity of the input signal magnetic field Hi is increased. It is done.

  FIG. 5 shows a set of GMR elements 14 and a coil 37 constituting the magnetoresistive element circuit 5A. The magnetization direction P of the pinned layer of the GMR element 14 is the + x direction. The direction of the input signal magnetic field Hi generated from the coil 37 is also the + x direction. Therefore, when there is no disturbance magnetic field Hn, the input signal magnetic field Hi is applied to the GMR element 14 in the same direction as the magnetization direction P of the pinned layer. On the other hand, when the disturbance magnetic field Hn in the direction as shown in FIG. 5 is generated, the combined magnetic field Hm of the input signal magnetic field Hi and the disturbance magnetic field Hn is applied to the GMR element 14 as shown in FIG. Thus, the direction and strength of the applied magnetic field applied to the GMR element 14 varies depending on the presence or absence of the disturbance magnetic field Hn. It also varies depending on the direction and strength of the generated disturbance magnetic field Hn. For example, when the direction of the disturbance magnetic field Hn is the following four directions, the influence of the disturbance magnetic field Hn on one GMR element 14 is as follows.

[1] When the direction of the disturbance magnetic field Hn is the ± x direction Since the input signal magnetic field Hi is applied with the disturbance magnetic field Hn applied as an offset, the resistance value of the GMR element 14 changes compared to the state without the disturbance magnetic field Hn. The amount does not change.
[2] When the direction of the disturbance magnetic field Hn is the + y direction Since the anisotropic magnetic field Hk is strengthened, fluctuations in the magnetization direction due to the input signal magnetic field Hi can be suppressed, and the resistance value of the GMR element 14 can be reduced as compared with the state without the disturbance magnetic field Hn. The amount of change decreases (resistance value increases).
[3] When the direction of the disturbance magnetic field Hn is in the -y direction Since the anisotropic magnetic field Hk is weakened, fluctuations in the magnetization direction due to the input signal magnetic field Hi increase, and the resistance value of the GMR element 14 is higher than in the state without the disturbance magnetic field Hn. The amount of change increases (resistance value decreases).

  Next, consider the influence of the disturbance magnetic field Hn on the four GMR elements 11 to 14 of the magnetoresistive element circuit 5A when the disturbance magnetic field Hn in the + x direction is generated as shown in FIG. In this case, the GMR element 11 is affected by the disturbance magnetic field Hn corresponding to the above [3], and the GMR element 13 is affected by the disturbance magnetic field Hn corresponding to the above [2]. Further, the GMR elements 12 and 14 are affected by the effect corresponding to the above [1]. Therefore, the influence of the disturbance magnetic field Hn on the GMR element 11 and the influence of the disturbance magnetic field Hn on the GMR element 13 are offset. Such cancellation of the influence of the disturbance magnetic field is performed not only in the magnetoresistive element circuit 5A but also in other magnetoresistive element circuits 5B, 6A and 6B.

  In the magnetoresistive element circuits 5A and 5B, the magnetization direction P of the pin layer of the GMR element and the direction of the input signal magnetic field Hi are the same, whereas in the magnetoresistive element circuits 6A and 6B, the pin layer of the GMR element. Is opposite to the direction of the input signal magnetic field Hi. Thus, the resistance value of the GMR element differs depending on the direction of the input signal magnetic field Hi. More specifically, the resistance value of the GMR element is larger when the direction of magnetization of the pinned layer P and the direction of the input signal magnetic field Hi are opposite than when the directions of both are opposite. Therefore, in the bridge circuit 1, when a current corresponding to the input signal is supplied to the coils 31 to 38, the resistance value Ra of the magnetoresistive element circuit 5A (the combined resistance value of the GMR elements 11 to 14) and the magnetoresistive element circuit 5B Resistance value Rd (combined resistance value of GMR elements 25 to 28), resistance value Rb of magnetoresistive element circuit 6A (combined resistance value of GMR elements 15 to 18), and resistance value Rc of magnetoresistive element circuit 6B (GMR element 21) The combined resistance value of ˜24 is Ra = Rd <Rb = Rc.

  In the bridge circuit 1 of FIG. 2, when the current corresponding to the input signal is not supplied to the coils 31 to 38, Ra = Rb = Rc = Rd in both cases where the disturbance magnetic field Hn is present and not, and the bridge The output voltage (V1-V2) of the circuit 1 becomes zero. Note that the values of Ra, Rb, Rc, and Rd do not vary depending on the presence or absence of the disturbance magnetic field Hn, the strength of the disturbance magnetic field Hn, and the like.

  On the other hand, when the uniform disturbance magnetic field Hn is applied to the bridge circuit 1 from the outside of the IC chip 3 and the current corresponding to the input signal is supplied to the coils 31 to 38, as described above. Ra = Rd <Rb = Rc. Therefore, the output voltage (V1-V2) of the bridge circuit 1 is 0 when no current is supplied to the coils 31 to 38, but a difference occurs. Therefore, by detecting the input signal magnetic field Hi using the output voltage of the bridge circuit 1 when current is supplied to the coils 31 to 38, the disturbance magnetic field Hn can be applied to the disturbance magnetic field Hn in any direction. The influence of can be canceled.

<2. Modification>
The present invention is not limited to the above-described embodiment, and for example, the following modifications are possible. Moreover, you may combine the 2 or more deformation | transformation shown below suitably.

(1) A half-bridge circuit that excludes the magnetoresistive element circuits 6B and 5B and the second midpoint terminal T2b from the configuration of FIG. Moreover, it is good also as a half bridge circuit remove | excluding the magnetoresistive element circuits 5A and 6A and 1st midpoint terminal T2a from the structure of FIG. For example, in the case of the former configuration, when there is a disturbance magnetic field Hn and a current corresponding to an input signal is supplied to the coils 31 to 38, the resistance value Ra of the magnetoresistive element circuit 5A and the magnetoresistive element circuit 6A The resistance value Rb becomes a value corresponding to the change in resistance value due to the disturbance magnetic field Hn and each input signal magnetic field Hi, but whether the magnetization direction P of the pinned layer of the GMR element is the same as the direction of the input signal magnetic field Hi? Depending on whether or not, Ra <Rb. In addition, since both the magnetoresistive element circuits 5A and 6A constituting the half bridge circuit are affected by the disturbance magnetic field Hn, the influence of the disturbance magnetic field Hn is canceled from the first middle point potential V1. Therefore, the influence of the disturbance magnetic field Hn can be canceled by detecting the input signal magnetic field Hi using the first midpoint potential V1 when a current is supplied to the coils 31 to 38.

(2) Focusing on the magnetoresistive element circuit 5A, for example, when there is a disturbance magnetic field Hn and no current corresponding to the input signal is supplied to the coils 31, 33, 35 and 37, the resistance of the magnetoresistive element circuit 5A The value Ra is a constant value that does not depend on the disturbance magnetic field Hn. On the other hand, when there is a disturbance magnetic field Hn and a current corresponding to the input signal is supplied to the coils 31, 33, 35, and 37, the resistance value Ra of the magnetoresistive element circuit 5A is the disturbance magnetic field Hn and each input signal magnetic field. It becomes a value corresponding to a change in resistance value due to Hi. Therefore, since it is possible to detect the input signal magnetic field Hi using both, the magnetoresistive element circuit 5A or 5B may be used alone. The same applies to the magnetoresistive element circuits 6A and 6B.

  In the case of the bridge circuit 1 described in the embodiment, the measurement for detecting the input signal magnetic field Hi may be performed only when the current corresponding to the input signal is supplied to the coils 31 to 38. It is not necessary to perform measurement when no current is supplied to .about.38 or to hold the measured value obtained in that case.

(3) In the above-described embodiment, the four GMR elements connected in series are arranged so that the magnetization direction P of the pinned layer is shifted by 90 degrees. However, the arrangement is not limited to 90 degrees, and is arranged at other angles. May be. However, in order to suppress the influence of the disturbance magnetic field Hn as much as possible, it is preferable to dispose them by approximately 90 degrees.

(4) In the above-described embodiment, the coil is arranged so that the magnetization direction P of the pinned layer of the GMR element is the same as or opposite to the direction of the input signal magnetic field Hi. The reverse case is not limited. However, since the detection sensitivity can be maximized when both directions are the same or opposite, it is preferable to arrange the coils so that both directions are substantially the same or substantially opposite.

(5) The magnetoresistive element circuit and the bridge circuit according to the present invention are used in, for example, isolators, current sensors, AC adapters, etc., and are mounted on various electronic devices.

  DESCRIPTION OF SYMBOLS 1 ... Bridge circuit, 3 ... IC chip, T1a ... High power supply terminal, T1b ... Low power supply terminal, T2a ... 1st midpoint terminal, T2b ... 2nd midpoint terminal, AD ... Path | routes 11, 18, 21- 28 (12A-12C, 17A-17C, 22A-22C, 27A-27C) ... GMR element, 31-38 ... coil, 5A, 5B, 6A, 6B ... magnetoresistive element circuit, VDD ... high power supply potential, VSS ... low Power supply potential, V1 ... first midpoint potential, V2 ... second midpoint potential, 40, 41 ... wiring pattern, 50 ... comparator, Ra ... resistance value of magnetoresistive element circuit 5A, Rb ... resistance of magnetoresistive element circuit 6A Value, Rc: resistance value of magnetoresistive element circuit 6B, Rd: resistance value of magnetoresistive element circuit 5B, Vout: output signal, P: magnetization direction of pinned layer, Hi: input signal magnetic field, Hn: disturbance magnetic field, Hk ... Anisotropic magnetic field, Hm The combined magnetic field.

Claims (5)

Comprising four GMR elements connected in series between a first terminal and a second terminal;
When the four GMR elements are a first GMR element, a second GMR element, a third GMR element, and a fourth GMR element, the magnetization direction of the pinned layer of the first GMR element is used as a reference. As described above, the magnetization direction of the pinned layer of the second GMR element, the magnetization direction of the pinned layer of the third GMR element, and the magnetization direction of the pinned layer of the fourth GMR element are shifted by approximately 90 degrees. The first to fourth GMR elements are disposed;
A first coil magnetically coupled to the first GMR element;
A second coil magnetically coupled to the second GMR element;
A third coil magnetically coupled to the third GMR element;
A fourth coil magnetically coupled to the fourth GMR element;
A magnetoresistive element circuit. The magnetization direction of the pinned layer of the first GMR element and the direction of the magnetic field generated from the first coil, the magnetization direction of the pinned layer of the second GMR element and the direction of the magnetic field generated from the second coil, The magnetization direction of the pinned layer of the third GMR element and the direction of the magnetic field generated from the third coil, and the magnetization direction of the pinned layer of the fourth GMR element and the direction of the magnetic field generated from the fourth coil. Are arranged such that the first to fourth coils are substantially the same.
The magnetoresistive element circuit according to claim 1. The magnetization direction of the pinned layer of the first GMR element and the direction of the magnetic field generated from the first coil, the magnetization direction of the pinned layer of the second GMR element and the direction of the magnetic field generated from the second coil, The magnetization direction of the pinned layer of the third GMR element and the direction of the magnetic field generated from the third coil, and the magnetization direction of the pinned layer of the fourth GMR element and the direction of the magnetic field generated from the fourth coil. Are arranged such that the first to fourth coils are substantially reversed.
The magnetoresistive element circuit according to claim 1. A first power supply terminal to which a first power supply potential is supplied;
A second power supply terminal to which a second power supply potential is supplied;
A midpoint terminal;
A first magnetoresistive element circuit provided between the first power supply terminal and the midpoint terminal;
A second magnetoresistive element circuit provided between the midpoint terminal and the second power supply terminal;
The first magnetoresistive element circuit is the magnetoresistive element circuit according to claim 2,
The second magnetoresistive element circuit is the magnetoresistive element circuit according to claim 3,
A bridge circuit characterized by that. A high power supply terminal to which a high power supply potential is supplied;
A low power supply terminal to which a low power supply potential is supplied; and
A first midpoint terminal;
A second midpoint terminal;
A first magnetoresistive element circuit provided between the high power supply terminal and the first midpoint terminal;
A second magnetoresistive element circuit provided between the first midpoint terminal and the low power supply terminal;
The second magnetoresistive element circuit provided between the high power supply terminal and the second midpoint terminal;
The first magnetoresistive element circuit provided between the second midpoint terminal and the low power supply terminal;
The first magnetoresistive element circuit is the magnetoresistive element circuit according to claim 2,
The second magnetoresistive element circuit is the magnetoresistive element circuit according to claim 3,
A bridge circuit characterized by that.

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