JPH07220206A - Magneto-resistance effect element reproducing circuit - Google Patents

Abstract

PURPOSE:To unnecessitate a coupling capacitor and to reduce the cost by connecting an output of a differential amplifier circuit to a current control input of a current source and making the output of the differential amplifier circuit a reproducing output. CONSTITUTION:The magneto-resistance effect element reproducing circuit is equipped with a magneto-resistance effect element 2 whose resistance value is varied according to an input magnetic field, a transistor 4 as a current source for supplying a sense current to this element 2, a voltage source 7 for outputting a prescribed voltage and the differential amplifier circuit 6 having such inputs as an output voltage to be generated by making the sense current flow into the element 2 and an output voltage of a voltage source 5. The output of the differential amplifier circuit 6 is connected to the current control input of the current source 4, and then the output of the differential amplifier circuit 6 is rendered to be the reproducing output. By making feedback of the sense current, even when an initial value of the magneto-resistance effect element 2 as a resistance value at the time of no signal is varied due to its mass production, the output voltage of the element 2 is always equalized to the output voltage of the voltage source 5, so that amplifying operation is performed by the differential amplifier 6 without generating an abnormal offset. Consequently, no coupling capacitor is required.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reproducing apparatus using a magnetoresistive effect element in magnetic recording / reproducing.

[0002]

2. Description of the Related Art In recent years, magnetic recording / reproducing apparatuses typified by compact cassette tape recorders and video tape recorders have been popular with apparatuses using a coil type magnetic head.
On the other hand, there has been proposed a magnetic head using a magnetoresistive effect element that converts a change in magnetic field into a change in resistance by using a recent thin film forming technique. Since this head can be mass-produced, it is expected to be popularized by lowering the price in the future. A conventional example of a magnetic tape reproducing device using this head will be described below with reference to FIG.

In FIG. 10, 1 is a magnetic tape, 2 is a magnetoresistive element, 61 is a current source for supplying a sense current,
62 is a coupling capacitor, 63 is an amplifier, and 64 is an output terminal.

Regarding the conventional example configured as described above,
The operation will be described below. The resistance value of the magnetoresistive effect element 2 shows a constant initial value when the input magnetic field received from the magnetic tape 1 is zero, and when the input magnetic field from the magnetic tape 1 is present, the resistance change proportional to the strength thereof is used as the initial value. The total sum is shown. On the other hand, in the magnetoresistive effect element 2, a constant sense current flows from the current source 61 to the magnetoresistive effect element 2.
Therefore, when the input magnetic field is zero, a constant DC voltage, which is the product of the sense current and the initial value of the magnetoresistive effect element 2, appears across the magnetoresistive effect element 2. When there is an input magnetic field, a product voltage of the sense current and the total value of the magnetoresistive effect element 2 appears and becomes an output signal. With respect to this output signal, a constant DC voltage due to the initial value of the magnetoresistive element 2 is blocked by the coupling capacitor 62, and a signal voltage due to a resistance change corresponding to the input magnetic field is transmitted to the amplifier 63. The amplifier 63 amplifies this signal and outputs a reproduction signal to the output terminal 64.

[0005]

However, in the above-mentioned conventional configuration, the initial value of the magnetoresistive effect element 2 varies during mass production, and therefore the DC voltage which is the product of the sense current and the initial value of the magnetoresistive effect element 2 is generated. Variation (1 as an example
0-50 mV). The gain of the normal amplifier 63 is large (1000 times as an example). Therefore, in the case of this example, a voltage offset of 10V to 50V is generated in the output of the amplifier 63. Since a power supply voltage of 5V is normally used, an offset exceeding the power supply voltage is generated by the amplifier 63.
Will be saturated and become inoperable. Therefore, as in the conventional example, the coupling capacitor 62 for cutting off the DC voltage is required.

Further, in the case of performing multi-track recording consisting of 9 channels like the recent digital compact cassette tape recorder, 9 coupling capacitors are required, which is a very big obstacle for rationalization. .

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a magnetoresistive effect element reproducing circuit which does not require a coupling capacitor and can reduce the cost.

[0008]

In order to achieve this object, a magnetoresistive effect element reproducing circuit of the present invention includes a magnetoresistive effect element whose resistance value changes in response to an input magnetic field and the magnetoresistive effect element. A current source that supplies a sense current, a voltage source, and a differential amplifier circuit that receives the output voltage generated by the sense current flowing through the magnetoresistive effect element and the output voltage of the voltage source, The output of the differential amplifier circuit is connected to the current control input of the current source,
The output of the differential amplifier circuit is used as a reproduction output.

[0009]

According to the present invention, the current value of the current source is determined so that the output voltage of the magnetoresistive effect element is always equal to the output voltage of the voltage source. Therefore, even if the initial value of the magnetoresistive element varies during mass production, the output voltage of the magnetoresistive element is constant, so that the differential amplifier circuit operates normally without shifting the operating point. Therefore, conventionally, a capacitor that is used for coupling the output of the magnetoresistive element and the amplifier and cuts off the DC voltage becomes unnecessary.

[0010]

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

FIG. 1 shows the configuration of an audio signal reproducing apparatus using a magnetic tape according to the first embodiment of the present invention. In FIG. 1, 1 is a magnetic tape as a magnetic recording medium, 2 is a magnetoresistive effect element, 3 is a power supply terminal, 4 is a transistor forming a current source, 5 is a voltage source, 6 is a differential amplifier circuit, and 7 is a resistor. , 8 are output terminals.

The operation of the audio signal reproducing apparatus using the magnetic tape of the present embodiment having the above-mentioned structure will be described below with reference to FIG. 2 showing operation waveforms of respective parts.

2A shows the magnetization of the tape, FIG. 2B shows the resistance value of the magnetoresistive element, FIG. 2C shows the sense current, and FIG.
Indicates the output voltage of the magnetoresistive effect element, area 1 indicates the case where nothing is recorded on the magnetic tape 1, and area 2 indicates the case where an audio signal is recorded on the magnetic tape 1 as a change in the strength of magnetization. ing.

First, consider a case where nothing is recorded on the magnetic tape 1 in the area 1. At this time, since the magnetic field input to the magnetoresistive effect element 2 is zero as shown in (a), the resistance value of the magnetoresistive effect element 2 shows an initial value as shown in (b). The current source that determines the sense current flowing through the magnetoresistive effect element 2 is composed of the transistor 4. The base of the transistor 4 has a resistor 7 connected to the output of the differential amplifier 6.
And the output of the differential amplifier 6 is fed back.
By this feedback, the transistor 4 becomes the magnetoresistive effect element 2
To supply a sense current whose output voltage is always the same as the output voltage of the voltage source 5. The sense current is constant as shown in (c). The output voltage of the magnetoresistive effect element 2 is equal to the output voltage of the voltage source 5 as shown in (d).

Next, consider a case where an audio signal is recorded on the magnetic tape 1 in the area 2 as a change in the strength of magnetization. Magnetoresistive element 2 near magnetic tape 1
The resistance value of 1 changes in proportion to the change of the input magnetic field from the magnetic tape 1 as shown in (b). As in the case of no signal (that is, the region 1), the collector current (sense current) of the transistor 4 flows so that the output voltage of the magnetoresistive effect element 2 becomes the same as the output voltage of the voltage source 5. The sense current at this time changes as shown in (c). The output voltage of the magnetoresistive element 2 is always the voltage source 5 as shown in (d).
Is equal to the output voltage of. Therefore, the differential amplifier circuit 6 is always in operation.

An example of the differential amplifier circuit 6 is shown in FIG. In the figure, 11 is a negative phase (-) input terminal, 12 is a positive phase (+) input terminal, 13 is an output terminal, 14 is a power supply terminal, 15, 16, 17, 19, 20, 21, 22, 23.
Is a transistor and 18 is a resistor. The operation will be described below. The transistors 15, 16 and 17 form a current mirror, and a current determined by the power supply voltage, the base-emitter voltage of the transistor 17 and the resistor 18 is supplied from the collectors of the transistors 15 and 16 to the connected circuit. The transistors 19 and 20 form a differential pair, and the collector current of the transistor 19 appears in the collector current of the transistor 22 in the current mirror composed of the transistors 21 and 22. The difference between the collector current of the transistor 22 and the collector current of the transistor 20 is output to the transistor 23, amplified by the transistor 23, and an output is obtained. With the above operation, the function of the differential amplifier 6 is fulfilled.

According to the present embodiment configured as described above, by feeding back the sense current, even if the initial value which is the resistance value of the magnetoresistive effect element 2 when there is no signal varies due to mass production, Since the output voltage of the resistance effect element 2 is always equal to the output voltage of the voltage source 5, the differential amplifier 6 performs an amplifying operation without generating an abnormal offset. Therefore, the conventionally used coupling capacitors are not required.

FIG. 4 shows the structure of an audio signal reproducing apparatus using a magnetic tape according to the second embodiment of the present invention.
In the figure, 1 is a magnetic tape which is a magnetic recording medium, 2
Is a magnetoresistive effect element, 4 is a transistor forming a first current source, 5 is a voltage source, 6 is a differential amplifier circuit, 7 is a resistor,
Reference numeral 31 is a transistor forming a second current source, 32 is an operational amplifier, 33 is a resistor, 34 is a power supply terminal, and 35 is an output terminal.

The operation of the audio signal reproducing apparatus using the magnetic tape of this embodiment having the above-mentioned structure will be described below. The operations of the magnetic tape 1, the magnetoresistive effect element 2, the transistor 4, the voltage source 5, the differential amplifier circuit 6, and the resistor 7 are the same as those in the case of FIG. An operation different from that in the embodiment will be described. As described in the first embodiment, the sense current output from the first current source is a current value at which the output voltage of the magnetoresistive effect element 2 becomes equal to the output voltage of the voltage source 5. Further, when the resistance of the magnetoresistive effect element 2 changes in response to the signal magnetic field generated from the magnetic tape 1, the sense current corresponds to the signal magnetic field so that the output voltage of the magnetoresistive effect element 2 is always constant. Change. Therefore, the sense current can be output as a signal. Here, since the base and the emitter of the transistor 4 forming the first current source and the transistor 31 forming the second current source are connected to each other, their collector currents are equal to each other. Therefore, the output current of the transistor 31 forming the second current source becomes the output signal current corresponding to the signal magnetic field. This output signal current is amplified by the operational amplifier 32 and the resistor 33 and output to the output terminal 35. As the operational amplifier used here, a general-purpose IC such as AN4558 manufactured by Matsushita Electronic Industrial Co., Ltd. can be used.

According to the present embodiment configured as described above,
By feeding back the sense current as in the first embodiment, the same effect as in the first embodiment can be obtained. Further, since a current equal to the sense current when the output voltage of the magnetoresistive effect element 2 becomes constant becomes an output signal, an output current with a small waveform distortion that corresponds accurately to the resistance change of the magnetoresistive effect element 2 can be obtained. .

FIG. 5 shows the structure of an audio signal reproducing apparatus using a magnetic tape according to the third embodiment of the present invention.
In FIG. 5, 1 is a magnetic tape which is a magnetic recording medium, 2
Is a magnetoresistive element, 3 is a power supply terminal, 38 is a third current source for supplying a sense current, 37 is a transistor forming a fourth current source, 36 is a resistor, 6 is a differential amplifier circuit, and 7 is a resistor. , 39 are output terminals.

The operation of the audio signal reproducing apparatus using the magnetic tape of the present embodiment having the above-mentioned structure will be described below with reference to FIG. 6 which shows operation waveforms of respective parts.

6A shows the magnetization of the tape, FIG. 6B shows the resistance value of the magnetoresistive element 2, FIG. 6C shows the output current of the fourth current source, and FIG. 6D shows the voltage of the resistor 36. Area 1 shows a case where nothing is recorded on the magnetic tape 1, and area 2 shows a case where an audio signal is recorded on the magnetic tape 1 as a change in the strength of magnetization.

First, consider the case where nothing is recorded on the magnetic tape 1 in the area 1. At this time, since the magnetic field input to the magnetoresistive effect element 2 is zero as shown in (a), the resistance value of the magnetoresistive effect element 2 shows an initial value,
The output voltage due to the sense current has a constant value as shown in (b). The voltage of the resistor 36 is the product of the value of the resistor 36 and the value of the collector current of the transistor 37 forming the fourth current source, as shown in (d). The output of the differential amplifier 6 is connected to the base of the transistor 37 via the resistor 7, and the output of the differential amplifier 6 is fed back. Due to this feedback, the collector current of the transistor 37 in which the voltage of the resistor 36 is always the same as the output voltage of the magnetoresistive effect element 2 flows. (C) shows the collector current of the transistor 37 which is the fourth current source. (D) is the voltage of the resistor 36,
It is equal to the output voltage of the magnetoresistive effect element 2.

Next, consider a case where an audio signal is recorded on the magnetic tape 1 in the area 2 as a change in the strength of magnetization. Magnetoresistive element 2 near magnetic tape 1
The output voltage of 1 changes in proportion to the change of the input magnetic field from the magnetic tape 1 as shown in (b). (C) shows the collector current of the transistor 37 which is the fourth current source. As in the case of no signal (that is, the region 1), the collector current of the transistor 37 flows so that the voltage of the resistor 36 becomes the same as the output voltage of the magnetoresistive effect element 2. The collector current of the transistor 37 at this time is shown in (d). The output voltage of the resistor 36 is equal to the output voltage of the magnetoresistive effect element 2 as shown in (d). Therefore, the voltage of the resistor 36 is always equal to the output voltage of the magnetoresistive effect element 2,
The differential amplifier circuit 6 always holds the operating state.

Now, consider the value of the resistor 36. As an example, when the value of the resistor 36 is 50Ω which is the same as the initial value of the magnetoresistive effect element 2, the collector current of the transistor 37 becomes the same as the sense current and becomes about 10 mA. next,
If the value of the resistor 36 is, for example, 500Ω, the voltage is the same as in the previous example, and therefore the collector current of the transistor 37 is about 1 mA. In this way, by selecting a large value for the resistance 36 with respect to the initial value of the resistance of the magnetoresistive effect element 2, the collector current of the transistor 37 forming the fourth current source can be made lower than the sense current. . If the collector current becomes small, the differential amplifier circuit 6 having a small output current supply capability of the differential amplifier circuit 6 can be used.

According to the present embodiment configured as described above, the resistance of the magnetoresistive effect element 2 when there is no signal is fed back to the fourth current source for generating the current that determines the voltage of the resistor 3. Even if the initial value, which is a value, varies due to mass production, the voltage of the resistor 36 is always equal to the output voltage of the magnetoresistive effect element 2, so that the differential amplifier 6 performs an amplifying operation without generating an abnormal offset. Therefore, the conventionally used coupling capacitor is unnecessary, and the same effect as that of the first embodiment can be obtained. Further, in contrast to the first embodiment, this embodiment can reduce the collector current of the transistor 37 constituting the fourth current source as described above, and therefore uses a circuit having a small output current supply capability. Is something that can be done. Further, when this embodiment is applied to an integrated circuit, it becomes possible to use a transistor having a size smaller than that of the first embodiment, which contributes to a reduction in chip size and a reduction in IC cost. .

FIG. 7 shows the structure of an audio signal reproducing apparatus using a magnetic tape according to the fourth embodiment of the present invention.
In the figure, 1 is a magnetic tape which is a magnetic recording medium, 2
Is a magnetoresistive effect element, 38 is a third for supplying a sense current
Current source, 36 is a resistor, 37 is a transistor forming a fourth current source, 6 is a differential amplifier circuit, 7 is a resistor, 40 is a transistor forming a fifth current source, 32 is an operational amplifier, and 33 is Resistor, 34 is a power supply terminal, 35 is an output terminal, 4
1 is a bias voltage source.

The operation of the audio signal reproducing apparatus using the magnetic tape of the present embodiment having the above-mentioned structure will be described below. The operation of the magnetic tape 1, the magnetoresistive effect element 2, the transistor 4, the third current source 38, the resistor 36, the transistor 37 forming the fourth current source, the differential amplifier circuit 6, and the resistor 7 is shown in FIG. It is the same as the case of the third embodiment.

As described in the third embodiment, the output current of the fourth current source is a current value at which the voltage of the resistor 36 becomes equal to the output voltage of the magnetoresistive effect element 2. Furthermore, when the resistance of the magnetoresistive effect element 2 changes in response to the signal magnetic field generated from the magnetic tape 1 and the output voltage changes, the voltage of the resistor 36 is always equal to the output voltage of the magnetoresistive effect element 2. Thus, the collector current of the transistor 37 changes. Therefore, the collector current of the transistor 37 can be used as a signal output. Here, since the base and the emitter of the transistor 37 forming the fourth current source and the transistor 40 forming the fifth current source are connected to each other, their collector currents are equal to each other. Therefore,
The output current of the transistor 40 forming the fifth current source becomes an output signal current corresponding to the signal magnetic field. This output signal current is amplified by the operational amplifier 32 and the resistor 33 and output to the output terminal 35.

According to the present embodiment configured as described above,
Similar to the third embodiment, by feeding back the fourth current source that generates the current that determines the voltage of the resistor 36, the same effect as the third embodiment can be obtained. Furthermore, a current equal to the collector current of the transistor 37, which is proportional to the output voltage of the magnetoresistive effect element 2, becomes an output signal, so that an output current with a small waveform distortion that accurately corresponds to the resistance change of the magnetoresistive effect element 2 is obtained. .

FIG. 8 shows the structure of an audio signal reproducing apparatus using a magnetic tape according to the fifth embodiment of the present invention. In FIG. 8, 1 is a magnetic tape which is a magnetic recording medium, 2 is a magnetoresistive effect element, 42 is a resistor, 5 is a voltage source,
6 is a differential amplifier circuit, 43 and 44 are transistors, 45 and 46 are resistors, 47 is a power supply terminal, and 48 is an output terminal.

The operation of the audio signal reproducing apparatus using the magnetic tape of this embodiment having the above-mentioned structure will be described below. In the configuration of this embodiment, the current source composed of the transistor 4 in the first embodiment is replaced by the transistor 4
3 and 44, and a voltage source composed of a resistor 45 and a resistor 42. In the first embodiment, the output of the differential amplifier circuit 6 is connected to the current source via the resistor 7, and the collector of the transistor 4, which is the output of the current source, is connected to the magnetoresistive element 2. In the case of the present embodiment, the output of the differential amplifier circuit 6 is connected to the base of the transistor 44 forming the voltage source via the resistor 46, and the emitter of the transistor 43, which is the output of the voltage source, is magnetically connected via the resistor 42. It is connected to the resistance effect element 2. The collector current of the transistor 44 is the resistance 4
It is controlled by the output of the differential amplifier circuit 6 which is applied via 6. This collector current flows through the resistor 45, and a voltage obtained by subtracting the voltage drop across the resistor 45 from the voltage at the power supply terminal 47 appears at the collector of the transistor 44. Since the collector of the transistor 44 is connected to the base of the transistor 43, the emitter of the transistor 43, which is the output of the voltage source, outputs a voltage smaller than the collector voltage of the transistor 44 by the base-emitter voltage of the transistor 43. Therefore, the voltage controlled by the differential amplifier circuit 6 is output to the emitter of the transistor 43 which is the output of the voltage source. The output voltage causes a sense current to flow through the resistor 42 and the magnetoresistive effect element 2 and the output of the differential amplifier circuit 6 is fed back, so that the transistors 43 and 44 and the resistor 45 that constitute the voltage source of this embodiment are connected to each other. The circuit portion of the resistor 42 is the transistor 4 which constitutes the current source in the first embodiment.
Same operation as.

According to the present embodiment configured as described above, the same effect as that of the first embodiment can be obtained by feeding back the sense current via the voltage source.

FIG. 9 shows the structure of an audio signal reproducing apparatus using a magnetic tape according to the sixth embodiment of the present invention. In FIG. 9, 1 is a magnetic tape as a magnetic recording medium, 2 is a magnetoresistive element, 38 is a current source for supplying a sense current, 49 is a first resistor, 50 is a second resistor, and 6 is differential amplification. Circuits, 43 and 44 are transistors, 45 and 46
Is a resistor, 47 is a power supply terminal, and 48 is an output terminal.

The operation of the audio signal reproducing apparatus using the magnetic tape of this embodiment having the above-mentioned structure will be described below. In the configuration of this embodiment, the current source including the transistor 37 and the resistor 36 in the third embodiment, the voltage source including the transistors 43 and 44 and the resistor 45, and the first resistor are included.
The resistor 49 is replaced with the resistor. The third embodiment is
The output of the differential amplifier circuit 6 is connected to the current source via the resistor 7, and the collector of the transistor 37, which is the output of the current source, is connected to the magnetoresistive element 2. In the case of the present embodiment, the output of the differential amplifier circuit 6 is connected to the base of the transistor 44 constituting the voltage source via the resistor 46, and the emitter of the transistor 43, which is the output of the voltage source, is resistor via the resistor 49. Connected to 50. The collector current of the transistor 44 is controlled by the output of the differential amplifier circuit 6 applied via the resistor 46. This collector current flows through the resistor 45, and a voltage obtained by subtracting the voltage drop across the resistor 45 from the voltage at the power supply terminal 47 appears at the collector of the transistor 44. Since the collector of the transistor 44 is connected to the base of the transistor 43, the transistor 4 which is the output of the voltage source
The emitter of No. 3 outputs a voltage smaller than the collector voltage of the transistor 44 by the base-emitter voltage of the transistor 43. Therefore, the voltage obtained by feeding back the output of the differential amplifier circuit 6 is output to the emitter of the transistor 43 which is the output of the voltage source. This output voltage is divided by the first resistor 49 and the second resistor 50 and input to the differential amplifier circuit 6, and is simultaneously controlled by the differential amplifier circuit 6. Therefore, the voltage source of this embodiment is Transistor 43,
The circuit portion of 44, the resistor 45 and the first resistor 49 operates in the same manner as the transistor 37 constituting the current source in the third embodiment.

According to the present embodiment configured as described above, the same effect as that of the third embodiment is obtained by feeding back the voltage source for supplying the input voltage of the differential amplifier circuit 6. .

[0038]

As described above, according to the present invention, by feeding back the sense current supplied to the magnetoresistive effect element,
Even if the initial value of the resistance of the magnetoresistive effect element varies, the amplifying circuit can perform a normal amplifying operation without generating an abnormally large offset. Therefore,
Conventionally, there is no need for a coupling capacitor that blocks the scattered DC voltage that causes abnormal offset. This is effective in reducing the system cost. In particular, when 9-channel multi-track recording was performed as in the case of recent digital compact cassette tape recorders, 9 coupling capacitors were conventionally required, but these 9 capacitors were all abolished and the The cost can be reduced. Furthermore, in order to further rationalize the wiring of a magnetic recording system using multi-track multi-track in the future, a method of integrating a magnetic head portion using a magnetoresistive effect element and a circuit is effective. At this time, by using the present invention which does not require the use of a coupling capacitor that requires a large volume, it is possible to realize a multi-track configuration having more channels.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an audio signal reproducing device using a magnetic tape according to a first embodiment of the present invention.

FIG. 2 is an operation waveform diagram of each part of the audio signal reproducing device using the magnetic tape according to the first embodiment of the present invention.

FIG. 3 is a circuit diagram showing an example of a configuration of a differential amplifier circuit according to the first embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of an audio signal reproducing device using a magnetic tape according to a second embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of an audio signal reproducing device using a magnetic tape according to a third embodiment of the present invention.

FIG. 6 is an operation waveform diagram of each part of an audio signal reproducing device using a magnetic tape according to a third embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of an audio signal reproducing device using a magnetic tape according to a fourth embodiment of the present invention.

FIG. 8 is a block diagram showing a configuration of an audio signal reproducing device using a magnetic tape according to a fifth embodiment of the present invention.

FIG. 9 is a block diagram showing a configuration of an audio signal reproducing device using a magnetic tape according to a sixth embodiment of the present invention.

FIG. 10 is a block diagram showing a configuration of a magnetic tape reproducing device in a conventional example.

[Explanation of symbols]

 1 Magnetic Tape 2 Magnetoresistive Element 4 Transistor Constituting Current Source 5 Voltage Source 6 Differential Amplifier Circuit 8 Output Terminal

Claims (6)

[Claims] 1. A magnetoresistive effect element whose resistance value changes in response to an input magnetic field, a current source for supplying a sense current to the magnetoresistive effect element, a voltage source for outputting a predetermined voltage, and the sense current. Is provided with an output voltage generated by flowing through the magnetoresistive element and an output voltage of the voltage source, and an output of the differential amplifier circuit is used as a current control input of the current source. A magnetoresistive effect element reproducing circuit which is connected and which uses the output of the differential amplifier circuit as a reproducing output. 2. A magnetoresistive effect element whose resistance value changes in response to an input magnetic field, a first current source for supplying a sense current to the magnetoresistive effect element, and a voltage source for outputting a predetermined voltage. A differential amplifier circuit that receives an output voltage generated when the sense current flows through the magnetoresistive element and an output voltage of the voltage source, and outputs the output of the differential amplifier circuit to the first current. A magnetoresistive effect element reproducing circuit which uses the current control input of the first current source and the current output of a second current source having a current control input common to the current control input of the first current source as a reproduction output. 3. A magnetoresistive effect element whose resistance value changes in response to an input magnetic field, a first current source for supplying a sense current to the magnetoresistive effect element, and a resistor for generating a predetermined voltage. A second current source for supplying a current to the resistor; a voltage generated by the current of the second current source flowing through the resistor; and an output generated by the sense current flowing through the magnetoresistive element. And a differential amplifier circuit having a voltage as an input, the output of the differential amplifier circuit being a current control input of the second current source, and the output of the differential amplifier circuit being a reproduction output. Effect element reproduction circuit. 4. A magnetoresistive effect element whose resistance value changes in response to an input magnetic field, a first current source for supplying a current to the magnetoresistive effect element, and a resistor for generating a predetermined voltage. A second current source for supplying a current to the resistor; a voltage generated by the current of the second current source flowing through the resistor; and a current of the first current source flowing through the magnetoresistive effect element. A differential amplifier circuit that receives an output voltage generated by the second current source as an input, and an output of the differential amplifier circuit as a current control input of the second current source, and a current control input of the second current source. A magnetoresistive effect element reproducing circuit which uses a current output of a third current source having a common current control input as a reproducing output. 5. A magnetoresistive effect element whose resistance value changes in response to an input magnetic field, a resistor connected in series with the magnetoresistive effect element, and a voltage supplied to the magnetoresistive effect element and the resistor. A first voltage source, and a differential amplifier circuit having as inputs the voltage obtained by dividing the output of the first voltage source by the magnetoresistive effect element and the resistor and the output voltage of the second voltage source. A magnetoresistive effect element reproducing circuit comprising: an output of the differential amplifier circuit as a voltage control input of the first voltage source and an output of the differential amplifier circuit as a reproduction output. 6. A magnetoresistive effect element whose resistance value changes according to an input magnetic field, a current source for supplying a sense current to the magnetoresistive effect element, and a voltage which is divided to generate a predetermined voltage. A first and a second resistor connected in series for the purpose of: a voltage source for supplying a voltage to the first and the second resistor; and an output voltage generated by the sense current flowing through the magnetoresistive element. The output of the voltage source is the first
Differential amplifier circuit that receives the voltage divided by the second resistor and the second resistor as an input, the output of the differential amplifier circuit is used as a voltage control input of the voltage source, and the differential A magnetoresistive effect element reproduction circuit that uses the output of the amplifier circuit as the reproduction output.