JPH0718972Y2 - Magnetic detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a magnetic detection device for detecting a magnetic signal recorded on a magnetic recording medium by using a magnetoresistive element and outputting it as an electric signal.

(Prior Art) Magnetic detection for detecting a magnetic signal recorded on a magnetic recording medium by using a magnetoresistive element utilizing a magnetoresistive effect in which electric resistance of a ferromagnetic metal or a semiconductor is changed by the action of a magnetic field as a detection sensor. 2. Description of the Related Art Devices are known and widely used as sensors for magnetic signal detection, magnetic field measurement, displacement sensors, rotation speed sensors, rotation angle sensors, and the like.

FIG. 5 shows an example of a general configuration of a magnetic detection device using the magnetoresistive element.

Here, MR in the drawing indicates a magnetoresistive element, and this magnetoresistive element MR is composed of _two magnetoresistive stripes MR ₁ and MR ₂ whose resistance values are indicated by R ₁₁ and R ₁₂ , respectively. The magnetoresistive stripes MR ₁ and MR ₂ are arranged so as to face the magnetic recording medium 4, and magnetic signals of the magnetic recording medium 4, for example, N and S poles are alternately arranged at a constant cycle as shown in the figure. If the recording wavelength of the magnetic signal is λ, the distance between the _two magnetoresistive stripes MR ₁ and MR ₂ is usually set to λ / 4.

Also, one end side of each magnetic stripe MR ₁ , MR ₂ is connected to a common power supply voltage Vc, and the other end side is connected to a constant current source 5, 6, respectively.

Here, the magnetic signals detected by the magnetoresistive element MR are the voltages V ₁₁ and V _{12 of the} two magnetoresistive stripes MR ₁ and MR _2.
The difference V ₁₁ −V ₁₂ is detected as a differential output.

(Problems to be Solved by the Invention) By the way, in the magnetic detection device shown in FIG. 5, when the magnetoresistive element MR and the magnetic recording medium 4 are moved at a constant speed in the relative movement direction shown by F in the figure, it is detected. Above differential output
V ₁₁ −V ₁₂ becomes an approximate sine wave as shown in FIG.

However, each magnetoresistive stripe M of the magnetoresistive element MR
Since the resistance values of R ₁ and MR ₂ and the strength of the magnetic signal recorded on the magnetic recording medium 4 are affected by temperature, the detected amplitude A ₁ of the differential output V ₁₁ −V ₁₂ is As shown in FIG. 7, it has a temperature coefficient of about −1800 ppm / ° C.

Here, the reason why the amplitude of the differential output has a temperature coefficient of about −1800 ppm / ° C. will be described.

In FIG. 5, when the relative moving distance between the magnetoresistive element MR and the magnetic recording medium 4 is x, the magnetoresistive stripes MR ₁ , M
The resistance change of R _{2 is due to} the resistance of one magnetoresistive stripe MR ₁ R ₁₁
Based on (x), R ₁₂ (x) = R ₁₁ (x + λ / 4) ().

Now, it is assumed that a magnetic flux density of a recording signal, B (x) = Ba sin {(2π / λ) x} ... (), is applied to the magnetoresistive stripes MR ₁ and MR ₂ . Further, the resistance change rate with respect to the applied magnetic flux density of the magnetoresistive stripe is approximated to a quadratic curve as shown in FIG. 8 (a), and ρ (B (x)) = A {B (x)} ² (...) Suppose

Here, when a magnetic flux density as shown in FIG. 8 (b) is applied to the magnetoresistive stripe, the resistance change rate ρ (B (x)) changes as shown in FIG. 8 (c). That is, the magnetic flux density of the resistance value R ₁₁ of the magnetoresistive stripe MR ₁ on the reference side is B
When the resistance value at (x) = O (gauss) is R ₀ , R ₁₁ is expressed by the following equation.

_{R 11 (x) = R 0} {1-ρ (B (x))} ‥‥ () That is, when B (x) is applied, R ₁₁ (x) is R ₀ from R ₀
The resistance value decreases by ρ (B (x)).

Here, if the above equation () is written down using equations () and (), From the expression (), R ₁₂ (x) is expressed by the following expression.

Here, from FIG. 5, the differential output V ₁₁ (x) −V ₁₂ (x) of the magnetoresistive stripes MR ₁ and MR ₂ is V ₁₁ −V ₁₂ = Vc−R ₁₁ (x) I− {Vc −R ₁₂ (x) I} = {R ₁₂ (x) −R ₁₁ (x) I ... () Therefore, using the formulas () and (), V ₁₁ −V ₁₂ = −ABa ² R ₀ Icos {4π / λ) x}.

That is, the amplitude A ₁ of the differential output V ₁₁ (x) −V ₁₂ (x) is
As shown in the figure, it can be seen that A ₁ = ABa ² R ₀ I.

Therefore, from the amplitude A ₁ = ABa ² R ₀ I, the temperature coefficient of the amplitude A ₁ is four factors, A, Ba ² , R ₀ , I, that is, It can be seen that each temperature coefficient is affected.

Here, in the magnetic detection device shown in FIG. 5, since the temperature coefficient of the drive current is usually 0 ppm / ° C., the mutual influence of the three factors A, Ba, and R ₀ (A × Ba ² × R ₀ ) Temperature coefficient −1
800 ppm / ° C appears as the temperature coefficient of amplitude −1800 ppm / ° C.

However, since the temperature coefficients of the above three factors A, Ba, and R ₀ are values that are uniquely determined in terms of physical properties, it is impossible to make the temperature coefficients of each factor zero, so that the amplitude It is difficult to reduce the temperature coefficient to zero.

Therefore, in the magnetic detection device having the configuration shown in FIG. 5, since the amplitude A ₁ of the output signal V ₁₁ -V ₁₂ has a negative temperature characteristic, in order to eliminate the influence of the temperature of the output signal, The signal processing circuit connected had to be temperature compensated.

A magnetic detection device using a magnetoresistive element, which takes into consideration the temperature change of the resistance of the magnetoresistive element, is proposed as follows: (a) JP-A-61-91577 and (B) JP-A-61-86614. ing.

Here, in the magnetic detection device described in the above (a), the magnetoresistive element and one end of a resistor having the same temperature coefficient of resistance as the magnetoresistive element are connected to a common potential, and the other ends thereof are independent constant currents. It is characterized in that the voltage difference between the magnetoresistive element and the other end of the resistor is detected while being connected to the source.

In the magnetic detection device (differential sensor) described in B), two magnetoresistive elements are connected to each other at their adjacent terminals, and a current flows through the two magnetoresistive elements. In the operation sensor, a connection point of two magnetoresistive elements is grounded, and a voltage between free terminals of the magnetoresistive elements is taken out as a sensor output voltage. In order for the current to compensate for the change in the resistance value of the magnetoresistive element,
It is characterized by having an inverse dependence on temperature.

However, in each of the above a) and b), consideration is given to the temperature change of the resistance value of the magnetoresistive element, but no consideration is given to the influence of other factors, and moreover, the magnetic detection described above is not taken into consideration. There is no mention of the problem of the temperature coefficient of the amplitude of the output signal of the device, and no means for solving this problem is disclosed.

Therefore, even in the magnetic detection device described in the above a) and b), the above-mentioned problem of the temperature coefficient of the amplitude of the output signal cannot be solved.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a magnetic detection device in which temperature compensation is performed at the magnetic signal detection stage and the problem of temperature dependence of the output signal is solved.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a magnetoresistive element that is arranged to face a magnetic recording medium on which a magnetic signal is recorded and that detects the magnetic signal, and a voltage is applied to the magnetoresistive element. The magnetoresistive element includes a power supply for applying a voltage and a constant current source connected in series with the magnetoresistive element, and the magnetoresistive element is composed of one magnetoresistive stripe arranged at a predetermined interval.
When the magnetoresistive element is composed of one magnetoresistive stripe, one end of the magnetoresistive stripe is connected to the power source and the other end is connected to the constant current source to apply a constant current to the magnetoresistive stripe, thereby changing the output voltage of the magnetoresistive stripe. A sinusoidal output signal corresponding to the magnetic signal is detected, and when the magnetoresistive element is composed of two magnetoresistive stripes, one end side of the two magnetoresistive stripes is connected to a common power source and the other end side is a constant current. A magnetic source for detecting a sinusoidal output signal according to a magnetic signal from the output voltage difference (differential output) of both magnetoresistive stripes by connecting a constant current source to the two magnetoresistive stripes. In the detection device, the constant current source is a current control amplifier connected to the magnetoresistive stripe of the magnetoresistive element, and a magnetic field connected between the amplifier and the ground side. The current detection resistor for detecting the value of the current flowing through the resistor stripe, and at least two resistors connected in series between the power source and the ground side are formed, and an intermediate portion between the power source side resistor and the ground side resistor is connected to the amplifier. A reference voltage circuit for generating a reference voltage to the amplifier, wherein the amplifier is a current control element (transistor or the like) connected between the magnetoresistive stripe and the current detection resistor;
A negative input terminal to which the voltage at the connection between the current control element and the current detection resistor is input, a positive input terminal to which the reference voltage is input, and an output terminal that outputs a voltage to the control terminal of the current control element. And an operational amplifier for controlling the current flowing through the magnetoresistive stripe by feeding back the output voltage to the control terminal of the current control element so that the voltages input to the positive and negative input terminals become equal. The resistance on the ground side in the reference voltage circuit has a larger positive temperature coefficient than the resistance on the power supply side.

(Operation) In the present invention, the constant current source of the magnetic detection device is composed of an amplifier, a reference voltage circuit and a current detection resistor, and the amplifier is composed of a current control element (transistor (power transistor, FET) etc.) and an operational amplifier. A feedback type amplifier, in which the current value flowing in the magnetoresistive stripe of the magnetoresistive element is detected as a voltage applied to the current detecting resistor and is fed back to the negative input terminal of the operational amplifier of the amplifier, and the feedback voltage is positive. Since the current control element is controlled so as to be equal to the reference voltage input to the input terminal, the current flowing through the magnetoresistive stripe can be a constant current. In the present invention, the resistance on the ground side in the reference voltage circuit that generates a reference voltage for obtaining a constant current has a larger positive temperature coefficient than the resistance on the power supply side. Since the reference voltage can have a positive temperature coefficient, and thus the current flowing through the current detection resistor, that is, the current flowing through the magnetoresistive stripe, can have a positive temperature coefficient, the output of the magnetoresistive element The negative temperature coefficient of is canceled out, and the temperature dependence (temperature change) of the amplitude of the output signal of the magnetoresistive element can be removed.

(Embodiment) Hereinafter, the present invention will be described in detail based on an illustrated embodiment.

FIG. 1 shows an example of a schematic circuit configuration of a magnetic detection device according to the present invention. In the figure, reference symbol MR is two magnetoresistive stripes MR ₁ and MR ₂
A magnetoresistive element comprising:
MR ₁ and MR ₂ are arranged so as to face a magnetic recording medium 4 on which a magnetic signal (in the illustrated example, an example of a magnetic signal in which N and S poles are alternately recorded at a constant cycle is shown) is recorded. Reference numeral 1 in the figure indicates a constant current source connected in series with the magnetoresistive element.

Here, the overall structure of the magnetic detection device shown in FIG. 1 is almost the same as that shown in FIG. 5, but in the present invention, the constant current source 1 is used as the magnetoresistive stripe of the magnetoresistive element MR. An amplifier 2 for current control connected to MR ₁ and MR ₂ ,
The current detection resistors R ₁ and R ₂ connected between the amplifier 2 and the ground side for detecting the value of the current flowing in the magnetoresistive stripes MR ₁ and MR ₂ , and a series connection between the power supply Vc and the ground side. It consists of at least two resistors R ₄ and R ₅ connected, and the middle part of the power source side resistor R ₄ and the ground side resistor R ₅ is connected to the amplifier 2 and the reference voltage
The reference voltage circuit 3 for generating V _CNTL for the amplifier 2 is provided. Further, the amplifier 2, the MR stripe MR _1, MR ₂ and the current detection resistor R _1, a current control element connected between the R ₂ (transistor (power transistor, FET), etc.) TR _1, TR ₂ And the current control elements TR ₁ and TR ₂
And the reference voltage V _CNTL and the negative input terminal to which the voltage V _{2 at} the connection between the current detection resistors R ₁ and R ₂ (either one side is enough, R ₂ side in the example shown) is input. Voltage input to the positive and negative input terminals (V _CNTL , V ₂ ) that has a positive input terminal to be input and an output terminal that outputs a voltage to the control terminals of the current control elements TR ₁ and TR ₂ The output voltage V _out is fed back to the control terminals of the current control elements TR ₁ and TR ₂ so that they become equal to each other, and it is composed of an operational amplifier OP ₁ for controlling the current flowing in the magnetoresistive stripes MR ₁ and MR _2. There is.

Further, the present invention is characterized in that the resistance R ₅ on the ground side in the reference voltage circuit 3 has a larger positive temperature coefficient than the resistance R ₄ on the power supply side.

Hereinafter, as a more specific embodiment, an example in which an npn type power transistor is used as the current control element of the amplifier 2 will be described.

In the illustrated example, in the amplifier 2, the collector terminals are connected to the magnetoresistive stripes MR ₁ and MR ₂ of the magnetoresistive element MR, and the emitter terminals are connected to the current detection resistors R ₁ and MR ₂ , respectively.
_Two transistors TR ₁ and TR ₂ connected to R ₂ and its 2
The output terminals are connected to the base terminals of the _two transistors TR ₁ and TR ₂ via resistors, the positive input terminal to the reference voltage circuit 3 and the negative input terminal to the current detection resistors R ₁ and R _{2 2}
It is composed of an operational amplifier OP ₁ connected to the side.

The reference voltage circuit 3 has a configuration in which two resistors R ₄ and R ₅ are connected in series. The free terminal side of the resistor R ₄ is connected to the power supply voltage Vc and the free terminal side of the resistor R ₅ is grounded. Has been done. The positive input terminal of the operational amplifier OP ₁ is connected to the intermediate portion of the resistors R ₄ and R ₅ .

Here, the operational amplifier OP ₁ outputs the output voltage Vout such that the voltage V ₂ input to the negative input terminal and the voltage V _CNTL input to the positive input terminal become equal. The voltage V _CNTL of the reference voltage circuit 3 input to the positive input terminal of the operational amplifier OP ₁ is expressed by the following equation.

Incidentally, a resistor R ₃ connected to the output terminal of the operational amplifier OP ₁ in the amplifier 2 is provided for preventing oscillation. As the two transistors TR ₁ and TR ₂ , a dual transistor having _two transistors TR ₁ and TR _{2 in} one package is usually used.

The current detecting resistors R ₁ and R ₂ having the same resistance value and the same temperature coefficient are used.

The temperature coefficient of the resistor R ₄ in the reference voltage circuit 3 is 0 ppm / ° C.
A resistor with a temperature coefficient as close as possible to the
R ₅ is a positive temperature coefficient resistor, and the temperature coefficient of this resistor R ₅ is such that the temperature coefficient of the voltage V _CNTL input to the positive input terminal of the operational amplifier OP ₁ is positive. Greater than the temperature coefficient of R ₄ .

Incidentally, when the gain of the operational amplifier OP ₁ is small, the resistor R ₃ is
Alternatively, it can be omitted when h _{FE of} transistor TR ₂ is small.

By the way, in the magnetic detection device provided with the constant current source 1 having the above configuration, the current flowing from the base to the emitter of the _two transistors TR ₁ and TR ₂ is far greater than the currents I ₁₁ and I ₁₂ flowing from the collector to the emitter. Since it is small, it can be approximated that I ₁₁ flows in the current detection resistor R ₁ on one side and I ₁₂ flows in the other current detection resistor R ₂ .

Therefore, the operational amplifier OP ₁ outputs the output voltage so that the input voltages V ₂ , V ₂ = R ₂ I ₁₂ (2) of the negative input terminal and the reference voltage V _CNTL input to the positive input terminal are equal. Vout, that is, the base voltage V _B is output. That is, the following equation, I ₁₂ = V _CNTL / R ₂ (3) is established, and I ₁₂ is determined by V _CNTL and the resistance R ₂ . Here, the resistor R ₂ serves as a current detector.

If the base-emitter voltages of the _two transistors TR ₁ and TR ₂ are equal, then R ₁ I ₁₁ = R ₂ I ₁₂ (4) holds, and when R ₁ = R ₂ , I ₁₁ = I ₁₂ (5)

Therefore, if R ₁ = R ₂ , then the magnetoresistive stripe M
It will drive the R _1, MR ₂ with the same current value I ₁₁ = I _12. Further, this current value is determined by V _CNTL and R ₂ from the equation (3).

Since the resistor R ₅ of the reference voltage circuit 3 has a positive temperature coefficient as described above, the output voltage V _CNTL of the reference voltage circuit 3
Also has a positive temperature coefficient. Therefore, (3)
As is clear from the equation, the current flowing through the current detection resistor R ₂
I ₁₂ has a positive temperature coefficient, and the current I ₁₁ flowing through the current detection resistor R ₁ also has a positive temperature coefficient from the equation (5).

Therefore, in the magnetic detector according to the present invention having the configuration shown in FIG. 1, the resistance values of the resistors R ₄ and R ₅ of the reference voltage circuit 3 and the temperature coefficients of the currents I ₁₁ and I ₁₂ are +1800 ppm / ° C. By selecting the temperature coefficient, the output signal (differential voltage) V ₁₁ −V
The temperature dependence (temperature change) of the amplitude A ₁ of ₁₂ can be eliminated.

FIG. 2 shows the amplitude of the output signal of the magnetic detection device according to the present invention.
The relationship between A ₁ and temperature is shown. The amplitude A ₁ does not change with temperature, and therefore the amplitude has no temperature dependence.

FIG. 3 is a schematic circuit configuration diagram of a magnetic detection device showing another embodiment of the present invention. In this magnetic detection device, two resistors R ₅ of the reference voltage circuit 3 of the device shown in FIG. Resistor R
_It is divided into ₅₁ and R ₆ , and these two resistors R ₅₁ and R ₆ are connected in series.

Here, one resistor R ₅₁ is a stripe-shaped linear resistor formed on the same chip as the _two magnetoresistive stripes MR ₁ and MR ₂ of the magnetoresistive element MR, and its resistance value changes depending on the signal magnetic field. Magneto-resistive stripes MR ₁ and MR ₂ so as not to change
It is placed at a right angle. When the resistance value is desired to be increased, the pattern is reciprocated. Also, the other resistor R ₆ is
Like the other resistor R _{4 of the} reference voltage circuit 3, the temperature coefficient is smaller than that of the resistor R _{5 of the} circuit shown in FIG.
Those around ℃ are used.

By the way, when temperature compensation of the output signal is performed in the magnetic detection device, the more accurate the temperature compensation unit is, the closer the temperature sensor section of the temperature compensation circuit is to the temperature compensation target, that is, the magnetic resistance element and the magnetic recording medium. You can The magnetic detection device having the configuration shown in FIG. 3 is intended for this purpose, and the resistor R ₅₁ formed on the same chip as the magnetoresistive stripes MR ₁ and MR ₂ serves as a temperature sensor of the temperature compensation circuit. To fulfill.

The resistor R ₅₁ is made of the same material as the magnetoresistive element or a material having a similar temperature coefficient, and is set to have the same temperature coefficient as the magnetoresistive element. For example, in the case of a magnetoresistive element made of ferromagnetic metal Ni-Fe,
While having a temperature coefficient of ~4000ppm / ℃, this time resistor R ₅₁
Are also formed to have the same temperature coefficient.

Now, in the magnetic detection device having the configuration shown in FIG. 3, similarly to the magnetic detection device shown in FIG. 1, the reference voltage circuit 3 has a reference voltage V _{CNTL so that} the temperature coefficient of the reference voltage V _CNTL becomes 1800 ppm / ° C. By determining the resistance value of each of the resistors R ₄ , R ₅₁ , and R ₆ of 3, the temperature dependence of the amplitude of the differential output signal V ₁₁ −V ₁₂ can be removed. The resistor R ₆ can be omitted in some cases.

By the way, by substituting the equation (1) into the equation (3) used in the description of the magnetic detection device shown in FIG. Becomes From this equation, another temperature compensation method for I ₁₂ is as follows: A) The temperature coefficient of the power supply voltage Vc is +1800 ppm / ° C.

B) The temperature coefficient of resistance of the current detection resistors R ₁ and R ₂ is -1800ppm / ℃
And

There are two options.

However, regarding the temperature compensation method of the above A), the temperature coefficient of the power supply voltage Vc applied to the resistor R ₄ of the reference voltage circuit 3 of the magnetic detection device having the configuration shown in FIG. 1 is +1800 ppm / ° C.
However, a circuit for generating the reference voltage must be provided in addition to the power supply circuit for generating the power supply voltage Vc, which complicates the circuit configuration and increases the cost, which is not a good idea.

Further, in the temperature compensation method of the above B), the temperature coefficient of resistance of the current detection resistors R ₁ and R ₂ must be set to −1800 ppm / ° C. at the same time in order to satisfy the condition shown in the equation (5). That is, it is necessary to use two resistors having a special temperature coefficient of −1800 ppm / ° C. and good pair matching, and it takes time to select the resistors.

Therefore, as the temperature compensation of the magnetic detection device, the circuit configuration of the embodiment shown in FIGS. 1 and 3 can be realized more simply and cheaply.

In FIG. 1, the so-called incremental phase of the position encoder has been described, but the case of the origin (absolute) phase can be handled in the same manner.

Further, although the magnetic detecting device of the embodiment shown in FIGS. 1 and 3 is shown for the case of differential output, like the magnetic detecting device shown in FIG. 4, the magnetoresistive stripe MR ₂ has only one side. Even in the case of single output, temperature compensation of the output signal can be similarly performed.

Incidentally, in FIG. 4, the components denoted by the same reference numerals as those in FIG. 1 have the same functions, and the description thereof will be omitted.

(Effect of the Invention) As described above with reference to the illustrated embodiment, according to the present invention, the temperature coefficient of the amplitude of the output signal of the magnetic detection device can be set to zero.

Further, since the temperature compensation with high accuracy of the magnetic signal detection stage can be realized with a simple circuit configuration, the signal processing of the subsequent stage becomes easy.

Therefore, according to the present invention, it is possible to provide a low-cost circuit including the signal processing circuit in the subsequent stage, and to provide a high-performance magnetic detection device in which the temperature dependence of the output signal is eliminated. .

[Brief description of drawings]

FIG. 1 is a schematic circuit configuration diagram of a magnetic detection device showing an embodiment of the present invention, and FIG. 2 is a graph showing the relationship between the amplitude of the output signal of the magnetic detection device according to the present invention shown in FIG. 1 and the temperature. FIG. 3 is a schematic circuit configuration diagram of a magnetic detection device showing another embodiment of the present invention, FIG. 4 is a schematic circuit configuration diagram of a magnetic detection device showing yet another embodiment of the present invention, and FIG. FIG. 6 is a schematic circuit configuration diagram of a magnetic detection device showing an example of a technique, and FIG. 6 shows a magnetic signal recorded on the magnetic recording medium shown in FIG. 5 by moving a magnetoresistive element relative to the magnetic recording medium. FIG. 8 is a graph showing the time change of the output signal of the magnetic detection device when it is detected. FIG. 7 is a graph showing the relationship between the amplitude of the output signal of the conventional magnetic detection device shown in FIG. 5 and the temperature. ) Indicates the magnetic field applied to the magnetoresistive stripe of the magnetic detection device shown in FIG. A graph showing the relationship between the bundle density and the resistance change rate of the magnetoresistive stripe approximated to a quadratic curve. FIG. 8B shows the magnetic recording medium and the magnetoresistive element in the magnetic detection device having the configuration shown in FIG. FIG. 8 (c) is a graph showing an example of a change in the magnetic flux density applied to the magnetoresistive stripe when the and are moved relative to each other, and FIG. 8 (b) shows the magnetoresistive stripe in the magnetic detecting device shown in FIG. FIG. 9 is a graph showing the change in resistance change rate of the magnetoresistive stripe when the magnetic flux density as shown in FIG. 9 is applied. FIG. 9 shows the change rate of the resistance of the magnetoresistive stripe in the magnetic detection device shown in FIG. 7 is a graph showing a change in output signal when the output signal changes as shown in FIG. 1 ... Constant current source, 2 ... Amplifier, 3 ... Reference voltage circuit,
4 Magnetic recording medium, MR, magnetoresistive element, MR ₁ , MR ₂
Magneto-resistive stripe, OP _1, operational amplifier, R ₁ , R ₂
Resistance for current detection, R ₄ , R ₅ ... Resistance in reference voltage circuit,
TR ₁ , TR ₂ Transistor, Vc Power supply voltage.

Claims (1)

[Scope of utility model registration request] 1. A magnetoresistive element arranged to face a magnetic recording medium having a magnetic signal recorded thereon to detect the magnetic signal, a power supply for applying a voltage to the magnetoresistive element, and a series connection with the magnetoresistive element. A constant current source, wherein the magnetoresistive element comprises one or two magnetoresistive stripes arranged at a predetermined interval. When the magnetoresistive element comprises one magnetoresistive stripe, one end thereof is the power source. By connecting the other end side to the constant current source and flowing a constant current through the magnetoresistive stripe, a sinusoidal output signal corresponding to the magnetic signal is detected from the output voltage of the magnetoresistive stripe. In the case of two magnetoresistive stripes, one end of each of the two magnetoresistive stripes is connected to a common power source and the other end of each is connected to a constant current source.
In a magnetic detection device for detecting a sinusoidal output signal according to a magnetic signal from the output voltage difference (differential output) of both magnetoresistive stripes by applying a constant current of the same value to each of the magnetoresistive stripes, The source is an amplifier for current control connected to the magnetoresistive stripe of the magnetoresistive element, a current detection resistor connected between the amplifier and the ground side for detecting the current value flowing in the magnetoresistive stripe, A reference voltage circuit for connecting the power supply side resistor and the ground side resistor, wherein the intermediate portion of the power source side resistor and the ground side resistor is connected to the amplifier and generates a reference voltage to the amplifier; The amplifier includes a current control element (transistor or the like) connected between the magnetoresistive stripe and the current detection resistor,
A negative input terminal to which the voltage at the connection between the current control element and the current detection resistor is input, a positive input terminal to which the reference voltage is input, and an output terminal that outputs a voltage to the control terminal of the current control element. And an operational amplifier for controlling the current flowing through the magnetoresistive stripe by feeding back the output voltage to the control terminal of the current control element so that the voltages input to the positive and negative input terminals become equal. The magnetic detection device, wherein the ground side resistance in the reference voltage circuit has a positive temperature coefficient larger than that of the power supply side resistance.