JPH0729105A - Recording/reproducing circuit for magnetoresistance effect head - Google Patents

Abstract

PURPOSE:To enable demagnetization of (shielded core of) an MR head with an MR sense current only by externally providing a plurality of parts to a recording/reproducing circuit. CONSTITUTION:A sense current for extracting a change of resistance of an MR element 11 as a voltage with a sense current control circuit 27 is applied to an MR element 11 through an amplifier circuit 31 connected to a magnetoresistance effect element (MR element) 11 of a magnetoresistance effect type head. Simultaneously, a demagnetization current which is an AC current of which the ampitude is gradually reduced is also applied to the MR element 11 by the demagnization current control circuit 28.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistive head recording / reproducing circuit for recording / reproducing using a magnetoresistive magnetic head having a magnetoresistive element.

[0002]

2. Description of the Related Art In a magnetoresistive effect type magnetic head (hereinafter referred to as an MR head), its magnetically sensitive portion is composed of a magnetic thin film having a magnetoresistive effect, and the resistivity of this magnetic thin film is magnetic on a magnetic recording medium. A current (sense current) flows through the magnetic thin film because it changes depending on the signal magnetic field based on recording.
To detect the resistance change as a reproduction output voltage. Since this MR head has features such as high output, low crosstalk, and no speed dependency, it is used as a reproducing head for a hard disk drive (HDD), or a high-density recording / reproducing head such as a digital audio tape recorder. Is used as.

As an example of such an MR head, FIG.
A shield type MR head as shown in FIG. 5 is known.

In FIG. 15, a shield type MR head 100 includes an upper (or upper layer) shield core 102.
The MR element 101 as a magnetic sensitive section made of one or a plurality of magnetic thin films having a magnetoresistive effect is provided in a space forming a predetermined reproducing gap G _R sandwiched between the lower shield core 103 and the lower (or lower) shield core 103. This MR element 1 is arranged
A pair of electrodes 105 for supplying a direct current as a sense current to 01 and extracting a resistance change as a voltage change.
a and 105b are electrically connected. A bias conductor 104 is provided in parallel with the MR element 101. For the shield cores 102 and 103 of the shield type MR head 100, a single bulk magnetic material, a single-layer plating film, a sputter film or the like is mainly used.

Further, FIG. 16 shows a so-called M in which an MR reproducing head and an ordinary inductive magnetic recording head are combined.
An example of the R inductive head is shown, and since the MR head part is configured in the same manner as the example of FIG. 15 described above, the same reference numerals are given to the corresponding parts and the description thereof will be omitted.

In FIG. 16, a predetermined recording gap G _{W is formed} on the upper shield core 102 of the MR head section.
The magnetic core 106 is provided via the
A spiral head winding 107 is provided so as to surround a magnetic coupling portion that is a connection portion with the shield core 102 of 6. In such an MR inductive head structure, the lower shield core 103 is provided on the base body or substrate 108 made of, for example, Al ₂ O ₃ —TiC, and the protective film layer 109 is laminated on the magnetic core 106 to form the gap. Is filled (or laminated) with a non-magnetic insulating material. The tip surface of the MR inductive head provided with the reproducing gap G _R and the recording gap G _W is a so-called ABS (air bearing surface) which is a surface facing a magnetic recording medium (for example, a hard disk).

FIG. 17 shows an example of a recording / reproducing IC (integrated circuit) for recording / reproducing using the MR inductive head as shown in FIG.

In FIG. 17, the MR inductive head 110 has a structure as shown in FIG. 16, for example.
MR element 111 and bias conductor 114 in FIG.
6 corresponds to the MR element 101 and the bias conductor 104, and the recording head 117 in FIG. 17 corresponds to the inductive head structure including the shield core 102, the magnetic core 106 and the head winding 107 in FIG. These MR element 111, bias conductor 114 and recording head 1
Reference numeral 17 denotes a connection terminal T of the MR inductive head 110.
Via terminals _{1 to} T ₆ , terminals T ₁₁ , T ₁₂ and T _{13 of} a recording / reproducing IC (MR inductive head recording / reproducing circuit) 120.
And so on. That is, one terminal T ₁ of the bias conductor 114 and one terminal T ₂ of the MR element 111 are grounded, and the other terminal T ₃ of the MR element 111.
Is connected to the amplifier circuit 131 in the W / R circuit section 130 via the terminal T ₁₁ of the recording / reproducing IC 120, and the magnetic head 1
Both terminals T ₄ and T ₅ of 17 are connected to a driver circuit 132 in a reproducing / recording (R / W) front circuit section 130 via terminals T ₁₂ and T ₁₃ of the recording / reproducing IC 120, respectively. The signals from the terminals T ₁₁ , T ₁₂ and T ₁₃ are respectively M
R (MR0), INX (IN0X), INY (IN0
Y). In the example of FIG. 17, such MR
It is configured so that four units (4 channels) of the unit of the inductive head 110 can be connected. FIG. 17
Since the bias conductor 114 shown in FIG. ₁ corresponds to one end of the four bias conductors connected in series, one terminal T ₁
Is grounded, and the other terminal T ₆ is connected to the bias conductor of the adjacent head. The other terminal of the bias conductor at the other end of the four bias conductors is the recording / reproducing IC 120.
Is connected to the bias current source 126 via the terminal T ₃₁ of the.

Next, the structure and operation of the recording / reproducing IC 120 will be described. The amplifier circuit 131 in the reproduction / recording front circuit unit 130 is a first-stage amplifier that amplifies the reproduction output from the MR head. Since the MR head is single-ended with one side grounded, the amplifier circuit 131 has a single-ended input and differential output. Has become. The reproduction output signal from the amplifier circuit 131 is the amplifier 121 which is the second-stage amplifier.
Are further amplified by and are taken out as signals RDY and RDX from the terminals T ₂₂ and T ₂₃ , respectively. The driver circuit 132 is a recording current driver and supplies a recording current to the recording head 117 during recording. These amplifier circuits 131
The driver circuits 132 are provided in four sets corresponding to the above four heads.

Mode control circuit 1 in recording / reproducing IC 120
22 to the playback / recording switching control signal R via a terminal T _24.
/ W, and the power save signal PS is supplied via the terminal T ₂₅ . This mode control circuit 22
It has the function of turning on the necessary circuits and turning off the unnecessary circuits in the playback, recording, and power save modes. When the reproduction / recording switching control signal R / W is "H" (high level), the reproduction (R) mode is set, the amplifier circuit 131, the amplifier 128, the bias current source 126, and the sense current control circuit 127 are turned on, and the driver Circuit 132, T-type flip-flop (T-FF) 1
24 and the recording current source 125 are turned off. When the reproduction / recording switching control signal R / W is "L" (low level), the recording (W) mode is set. Contrary to the above reproduction mode,
Amplifier circuit 131, amplifier 128, and bias current source 1
26, the sense current control circuit 127 is turned off, and the driver circuit 132, the T-FF 124, and the recording current source 125 are turned on. When the power save signal PS is "H" (high level), the power save (PS) mode is set, and all but the mode control circuit 122 are turned off, and the power consumption is kept low.

The head selection circuit 123 has a function of selecting a head to be used, and two (2-bit) selection control signals HS1 and HS0 supplied to terminals T ₂₆ and T ₂₇ , respectively.
Only the set of the amplifier 131 and the driver 132 corresponding to the head selected by the combination of is turned on. T-
An FF (T-type flip-flop) 124 is a flip-flop that switches the direction in which a recording current flows at the time of recording, and the write data signal WDI supplied to the terminal T ₂₈ is "H" →
The fall of "L" is used as a trigger to change the direction of the recording current to I.
Alternately switch between NX → INY and INY → INX.
The recording current source 125 is a circuit that sets the value of the recording current.
The recording current is set according to the control voltage WC obtained by the recording current setting resistor 125R connected to the terminal T ₂₉ .
Specifically, a recording current inversely proportional to the resistance value of the resistor 125R is passed from the driver 132 to the MR element 111. The sense current control circuit 127 is a circuit for setting the value of the sense current, and the sense current proportional to the sense current setting voltage VS supplied to the terminal T ₂₁ is supplied to the MR element 111 via the amplifier circuit 131. Bias current control circuit 1
Reference numeral 26 is a circuit for setting the value of the bias current, and the bias current IB proportional to the bias current setting voltage IBC supplied to the terminal T ₃₀ is supplied to the series circuit of the four bias conductors 114 and the like via the terminal T _31. Be done.

FIG. 18 shows only the reproducing amplifier connected to the MR element and the sense current control portion of the structure of the recording / reproducing IC 120. This FIG.
The configuration of FIG. 1 shows an example in which a so-called base-grounded transistor 135 is used for the first-stage amplifier.
The emitter of 35 is connected to the MR element 111 via the terminal T _11.
It is connected to the. The reproduction output is taken out from the connection point between the collector of the transistor 135 and the load resistor 136. The base potential of the transistor 135 is determined by the sense current control circuit 127, and the emitter potential MR0
Is determined, the sense current is determined from the potential and the resistance value of the MR element 111.

[0013]

However, the conventional shield type MR head as described above has the following problems. That is, when a winding type recording head is provided on the MR head to form a two-gap type recording / reproducing head, or a magnetic core of the winding type recording head and a shield core of the MR head are combined to form one-gap type recording. When a reproducing head is used, a large recording magnetic field is applied to the shield core from the recording head during recording. Therefore, when switching from recording to reproduction, the magnetic domain structure of the shield core may remain in a disordered state. Since the shield core is part of the magnetic path of the magnetic field from the magnetic medium, if the magnetic domain structure of the shield core is disturbed, there is a high possibility that noise due to domain wall movement, so-called Barkhausen noise, will occur. . Further, since the shield core is also a part of the magnetic path of the magnetic bias, the bias state becomes unstable and the reproduced signal waveform becomes unstable.

Even if an attempt is made to suppress a magnetic domain change due to a recording magnetic field by using a shield core in which two or more magnetic films are separated by a nonmagnetic film and laminated, it is difficult to completely stabilize the magnetic domains. Therefore, it is difficult to make the reproduced signal stable by completely converting the magnetic domain into a single magnetic domain.

By the way, it has been known that Barkhausen noise can be reduced by applying a magnetic field in the direction of the easy axis of magnetization. Therefore, it has been considered to stabilize the reproduction output by passing a current through the two-layer shield core, but this method may not be able to completely arrange the magnetic domain structure which is greatly disturbed during recording.

The present invention has been made in view of the above circumstances, and provides a recording / reproducing circuit for a magnetoresistive effect head capable of effectively demagnetizing the shield core of the magnetoresistive effect head. The purpose is.

[0017]

A recording / reproducing circuit for a magnetoresistive head according to the present invention comprises a recording circuit section for supplying a recording signal to the magnetoresistive head, and a magnetoresistive head. In a magnetoresistive head recording / reproducing circuit in which a reproducing circuit section for extracting a reproduced signal is integrated, an amplifier circuit connected to the magnetoresistive element of the magnetoresistive head as the reproducing circuit section, Sense current supply means for supplying a sense current for taking out a resistance change of the magnetoresistive effect element as a voltage via the amplifier circuit, and a gradual amplitude for demagnetizing the magnetoresistive effect element to the magnetoresistive effect element via the amplifier circuit. The above-mentioned problem is solved by having a degaussing current supply means for supplying an alternating current.

The magnetoresistive effect head has a magnetoresistive effect element and a shield core covering the magnetoresistive effect element, and the magnetoresistive effect element and the shield core are electrically connected to each other. Is preferably used.

Further, in the reproducing circuit section, the generation of the sense current and the generation of the degaussing current are performed at different timings (specifically, the sense current is passed after the degaussing current becomes zero). A delay means is provided, a voltage-current conversion means for converting the degaussing current control voltage to a degaussing current and outputting the degaussing current is provided in the amplifier circuit of the reproducing circuit section, and a degaussing current of the reproducing circuit section is provided. As a supply means, a triangular wave generating means for gradually reducing the amplitude,
It is preferable to use one having an alternating current signal generating means and a multiplying means for multiplying each output signal from the triangular wave generating means and the alternating current signal generating means.

[0020]

The shield core can be demagnetized by supplying the magnetoresistive effect element with an alternating current for degaussing which gradually decreases in amplitude and supplying a degaussing current to the sense current path.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block circuit diagram showing a schematic configuration of an embodiment of a recording / reproducing circuit for a magnetoresistive (MR) head according to the present invention, and FIG. 2 is a block circuit diagram showing an essential part thereof.

In FIG. 1, a terminal T ₁₁ of a recording / reproducing IC (integrated circuit) 20 as a recording / reproducing circuit for a magnetoresistive type magnetic head, a so-called MR head, is connected to the magnetic field of the MR head as shown in FIG. A resistance effect (MR) element 11 is connected. This MR head, as described later,
The magnetoresistive effect element (MR element) and the shield core are electrically connected to each other. The MR head (connection structure between the MR element and the shield core) has a DC sense current and a gradual amplitude. The degaussing current of the alternating current is reduced.

The recording / reproducing IC 20 shown in FIG. 1 is the same as that shown in FIG.
In the structure of the recording / reproducing IC 120 of FIG.
8 and a delay circuit 29 are added, and as a structure in the amplifier circuit 31, a g _m amplifier 37 as a voltage-current control means is added to the structure of FIG. 18 as shown in FIG. There is.

That is, the structure and operation of the recording / reproducing IC 20 of FIG. 1 will be described. The reproducing / recording front circuit section 30.
The amplifier circuit 31 therein is a first-stage amplifier that amplifies a reproduction output from the MR head. Since the MR head is a single-ended single-sided ground, the amplifier circuit 31 has a single-ended input and an output is differential. The reproduction output signal from the amplifier circuit 31 is the amplifier 21 which is the second-stage amplifier.
Are further amplified by and are taken out as signals RDY and RDX from the terminals T ₂₂ and T ₂₃ , respectively. Further, as shown in FIGS. 2 and 3, the amplifier circuit 31 causes the sense current set by the sense current control circuit 27 to flow through the MR element 11, and the gradual amplitude set by the degaussing current control circuit 28 is attenuated. MR of the demagnetizing current of the alternating current
It is passed through the element 11. The driver circuit 132 is a recording current driver and supplies a recording current to the recording head 117 during recording. The amplifier circuit 131 and the driver circuit 132 are provided in four sets corresponding to, for example, four heads (for four channels).

A mode control circuit 22 in the recording / reproducing IC 20.
To the playback / recording switching control signal R / W via a terminal T _24.
However, the power save signal PS is also supplied via the terminal T ₂₅ . The mode control circuit 22 has a function of turning on a necessary circuit and turning off an unnecessary circuit in each of the reproduction, recording, and power saving modes. When the reproduction / recording switching control signal R / W is "H" (high level), the reproduction (R) mode is set, the amplifier circuit 31, the amplifier 28, the bias current source 26 and the sense current control circuit 27 are turned on, and the driver The circuit 32, the T-type flip-flop (T-FF) 24, and the recording current source 25 are turned off. Playback / recording switching control signal R / W is "L"
At the time of (low level), the recording (W) mode is set. Contrary to the case of the reproduction mode, the amplifier circuit 31, the amplifier 2
8, the bias current source 26 and the sense current control circuit 27 are turned off, and the driver circuit 32, the T-FF 24 and the recording current source 25 are turned on. When the power save signal PS is "H" (high level), the power save (PS) mode is set, and all but the mode control circuit 22 are turned off.
Keep power consumption low.

The head selection circuit 23 is a circuit for selecting head used, the head selected by the two (2 bits) combination of the selection control signal HS1, HS0 of which are supplied to the terminal T _26, T ₂₇ Corresponding amplifier circuit 3
Only the set of 1 and the driver 32 is ON-controlled. T-FF
A (T-type flip-flop) 24 is a flip-flop for switching the direction of flow of a recording current at the time of recording, and has a terminal T _28.
Of the write data signal WDI supplied to the "H" → "L"
Of the recording current in INX →
Alternately switch between INY and INY → INX. The recording current source 25 is a circuit for setting the value of the recording current, and is a terminal T _29.
The recording current is set according to the control voltage WC obtained by the recording current setting resistor 25R connected to the. Specifically, a recording current inversely proportional to the resistance value of the resistor 25R is passed from the driver 32 to the MR element 11. The sense current control circuit 27 is a circuit for setting the value of the sense current, and the sense current proportional to the sense current setting voltage VS supplied to the terminal T ₂₁ is supplied to the MR element 11 via the amplifier circuit 31. An example of this sense current is shown in B of FIG. The bias current control circuit 26 is a circuit for setting the value of the bias current, and the bias current IB proportional to the bias current setting voltage IBC supplied to the terminal T ₃₀ is supplied to four bias conductors (not shown) via the terminal T _31. No)) flowed in the series circuit.

Further, the degaussing current control circuit 28 has a terminal T
_According to the initial amplitude data supplied to ₃₃ , the attenuation time data DT supplied to the terminal T ₃₄ , and the frequency data DF supplied to the terminal T ₃₅ , the initial amplitude, the attenuation time, and the frequency of the AC signal whose amplitude gradually decreases. Is set. Further, the delay circuit 29 delays (or does not delay) the mode control signal from the mode control circuit 22 in accordance with the delay control data supplied to the terminal T ₃₇ , and the sense current control circuit 27.
I am sending it to.

FIG. 3 shows only the reproducing amplifier connected to the MR element and the sense current control portion of the structure of the recording / reproducing IC 20. The configuration of FIG. 3 shows an example in which a so-called base-grounded transistor 35 is used in the first-stage amplifier, and the emitter of this transistor 35 is connected to the MR element 11 via the terminal T ₁₁ . The reproduction output is taken out from the connection point between the collector of the transistor 35 and the load resistance 36. Since the base potential of the transistor 35 is determined by the sense current control circuit 27 and the emitter potential MR0 is determined, the sense current is determined from the potential and the resistance value of the MR element 11. Moreover, the demagnetization current control signal from the demagnetization current control circuit 28 (voltage signal) Voltage - g _m amplifier 37 is a current converter
Is supplied to the emitter of the transistor 35 via, is added to the sense current from the emitter, and is supplied to the MR element 11.

Specific examples of the sense current and the degaussing current are shown in FIGS. First, in FIG. 4, when the reproduction / recording (R / W) mode changes as shown in A of FIG.
The sense current direct current of a current value I _s is given reproduction (R) mode to as B in FIG. 4, an alternating current (initial current amplitude value gradually reduced as shown in C of FIG. 4 in this sense current ± I _d ) is superimposed so that D of FIG.
A current as shown in is obtained. In the example of FIG. 4, the sense current and the degaussing current are made to flow simultaneously at the switching time t ₁ from the recording (W) mode to the reproducing (R) mode, but in addition to this, as shown in FIG. It is also possible to flow only the degaussing current at the end of recording (time t ₁ ), and to pass the sense current from time t _{3 at} which the passing of this degaussing current is completed.
Such timing control can be realized by controlling the delay time in the delay circuit 29.

Next, FIG. 6 shows the degaussing current control circuit 28.
3 is a block circuit diagram showing a specific example of FIG. In FIG. 6, the degaussing current control voltage generating circuit 28 includes a triangular wave generating circuit 28a, an AC signal generating circuit 28b, and these circuits 2
And a multiplier 28c for multiplying the output signals from 8a and 28b. The triangular wave generating circuit 28a is supplied with amplitude data DA for setting the initial current amplitude value of the degaussing current (above ± I _d ) and decay time data DT for setting the decay time of the amplitude, and the AC signal generating circuit 28b
Is supplied with frequency data DF for setting the frequency of the alternating current. The triangular wave generating circuit 28a outputs a triangular wave voltage having an amplitude and a decay time set based on the data DA and DT, and the AC signal generating circuit 2
The 8b outputs an AC voltage having a frequency set based on the data DF. These output signals are multiplied by the multiplier 28c and extracted as a gradually decreasing AC voltage signal as shown in C of FIG.

The initial amplitude value ± I _d of the degaussing current is set to a value large enough for the shield core of the MR head, which will be described later, to completely show a single domain structure.
The magnetic domain of the shield core is converged to a constant and stable state by changing from I _d to a repetitive wave shape that gradually decreases. Here, in the case of FIG. 4, when the sense current and the degaussing current are simply added, the peak value exceeds the above I _d (or falls below −I _d ), but a current above I _d is unnecessary. As shown in D of FIG. 4, the current may be cut (limited) by I _d . When I _d is a value that is not so large with respect to the sense current I _s , the degaussing current may lose the balance between the forward and reverse directions and the degaussing may not be successful. In this case, as shown in FIG. 5, the sense current may not be supplied while the degaussing current is flowing, and the original sense current may be supplied after the degaussing current becomes zero.

Next, some examples of specific structures of the MR head used in the embodiments of the present invention will be described with reference to the drawings.

FIG. 7 shows an example of a shield type magnetoresistive effect magnetic head (MR head) using two layers of magnetic films for the shield core. The MR head 10 shown in FIG.
In the above, the MR element 1 as a magnetically sensitive portion formed of a magnetic thin film of a single layer or a plurality of layers having a magnetoresistive effect has a predetermined size sandwiched between a pair of shield cores 2 and 3 (that is, the upper shield core 2 and the lower shield core 3). Are arranged in a space forming a gap G _R of A bias conductor 4 is arranged in parallel with the MR element 1 in the space between the shield cores 2 and 3.

One end of the one shield core (for example, the upper shield core) 2 on the reproduction gap G _R side has a non-magnetic conductor 5
It is electrically connected to the MR element 1 via a. MR
An electrode 5b is electrically connected to the other end of the element 1 and is taken out to the outside. The shield core 2 electrically connected to the MR element 1 has a structure in which two layers of magnetic films 2a and 2b are separated by a non-magnetic film 2c and laminated. An electrode 5c is electrically connected to the other end of the shield core 2 and is taken out to the outside. The direction of arrow J in the figure of such a shield core 2 is a hard axis of magnetization having a high magnetic permeability μ, and a current flows in this direction, so that the current flowing in one of the two magnetic films 2a and 2b is increased. Is applied to the easy axis of magnetization (direction of arrow K) of the other magnetic film 2b, 2a. MR head 1 in FIG. 1 above
1 mainly corresponds to the one in which the MR element 1 and the shield core 12 are electrically connected.

FIG. 8 shows an example in which such a head structure is applied to an MR inductive head of a magnetic disk device such as a hard disk. In this FIG.
The magnetic core 6 is arranged on the two-layer shield core 2 of FIG. 7 with a predetermined recording gap G _W interposed therebetween.
The spiral head winding 7 is provided so as to surround the magnetic coupling portion that is a connection portion with the shield core 2. In such an MR inductive head structure, the shield core 3 is provided on the base or substrate 8 made of, for example, Al ₂ O ₃ —TiC, and the protective film layer 9 is laminated on the magnetic core 6 so that the gap is provided between the gaps. Is filled (or laminated) with a non-magnetic insulating material. The so-called ABS (air-type air) in which the front end surface of the MR inductive head provided with the reproducing gap G _R and the recording gap G _W is the surface facing the magnetic recording medium (for example, hard disk).
Bearing surface).

With such a structure, a repetitive wave-shaped degaussing current that gradually decreases from a size (I _d above) sufficient for the shield core 2 to completely show a single domain structure at the start of reproduction is superimposed on the above sense current. Even if the magnetic domain of the shield core 2 is disturbed during recording, the magnetic domain of the shield core 2 will be in a constant and stable state during reproduction.
Since the bias magnetic field applied to the element 1 is stable and the magnetic path for the signal magnetic field is also stable, the reproduced signal can be stabilized without Barkhausen noise. Therefore,
Conventionally, it is possible to increase the linear recording density, which is limited by the instability of the reproduction signal. In addition, since the magnetic domain becomes unstable in the past, the width of the shield core, which could only be reduced to a certain extent, can be reduced, so that crosstalk from the adjacent tracks picked up via the shield core can be reduced, and the track density can be reduced. Can be improved, and the storage capacity of the magnetic disk device can be increased.

The MR head 10 used in the above embodiment has two magnetic films 2 on the upper shield core 2.
Although the structure in which a and 2b are laminated via the non-magnetic film 2c is used, an upper shield core 2'having a single layer structure may be used as shown in FIGS. 9 and 10. That is, FIG. 9 shows an MR corresponding to the MR head 10 of FIG.
A head 10 'is shown, and FIG. 10 shows a head corresponding to the MR inductive head of FIG. 9 and 10, the configuration is similar except that a single-layer shield core 2'is used in place of the two-layer magnetic film shield core 2 of FIGS. The same reference numerals are given to the parts and the description thereof will be omitted.

Next, FIG. 11 and FIG. 12 show an example of a conventional circuit configuration when a grounded-emitter transistor is used as the first stage amplifier of the MR head. The amplifier circuit 141 of FIG.
FIG. 12 shows a specific configuration example of the above. Since other configurations are the same as (a part of) FIG. 17 described above, the same reference numerals are given to the corresponding portions and the description thereof will be omitted.

In the amplifier circuit 141 of FIG. 11, as shown in FIG. 12, the MR element 111 receives a sense current control signal (voltage signal) from the sense current control circuit 127 as g _m.
The terminal voltage of the MR element 111 supplied via the amplifier 148 is sent to the base of the grounded-emitter transistor 145 via the capacitor 144. A current source 147 for supplying a base current is connected to a connection point between the base of the transistor 13 and the capacitor 12, and a load resistor 146 is connected to a collector of the transistor 145.

By applying the present invention to the recording / reproducing circuit having the common-emitter amplifier structure shown in FIGS. 11 and 12, another embodiment of the present invention as shown in FIGS. 13 and 14 can be constructed. it can. Here, in the configuration of FIG. 13, portions corresponding to those of the configuration of FIG. 2 are designated by the same reference numerals, and description thereof will be omitted. The amplifier circuit 41 used in this embodiment has a configuration as shown in FIG.

In FIG. 14, one end of the MR element 11 of the magnetoresistive head is grounded, the other end is supplied with a direct current serving as a sense current to be described later, and the output from the other end is a direct current. It is adapted to be supplied to the base of a grounded-emitter transistor 45, which serves as a first stage amplifier, via a cutting capacitor 44. A current source 47 for supplying a base current is connected to a connection point between the base of the transistor 45 and the capacitor 44, and a load resistor 46 is connected to a collector of the transistor 45. Here, when the resistance value of the MR element 11 through which the sense current flows changes due to the signal magnetic field, this is taken out as a change in voltage, amplified by the grounded-emitter transistor 45 via the DC cutting capacitor 44, and taken out.

As described above, the MR element 11 has a structure electrically connected to the shield core,
The MR element 11 is supplied with a DC sense current and an AC degaussing current that gradually decreases. That is, the output voltage from the sense current control circuit 27 and the output voltage from the degaussing current control circuit 28 are added by the adder 4
Is added by 9 Voltage - sent to g _m amplifier 48 is a current converter means, being sent is converted into a current to the MR element 11.

The present invention is not limited to the above-described embodiment. For example, a bias magnetic field generated by a bias current flowing through a bias conductor is used as the bias applied to the MR element. A body thin film may be placed instead of the bias conductor to apply the bias magnetic field. Further, although the shield type MR head has been described as an example in the above embodiment, the present invention can be applied to the yoke type MR head. In this case, the yoke core is formed in a two-layer structure instead of the shield core. The same effect can be obtained.

[0044]

As is apparent from the above description, according to the present invention, a recording circuit section for supplying a recording signal to the magnetoresistive head and a reproduction signal from the magnetoresistive head are provided. In a recording / reproducing circuit for a magnetoresistive effect head in which a reproducing circuit section to be taken out is integrated, the reproducing circuit section includes an amplifier circuit connected to a magnetoresistive effect element of the magnetoresistive effect head, and the amplifier circuit. A sense current supply means for supplying a sense current for extracting the resistance change of the magnetoresistive effect element as a voltage via the AC current which gradually reduces the degaussing amplitude to the magnetoresistive effect element via the amplifier circuit. And a degaussing current supplying means for supplying a degaussing current, the degaussing of the magnetoresistive head can be effectively performed with a simple configuration.

The magnetoresistive head has a magnetoresistive effect element and a shield core that covers the magnetoresistive effect element, and these magnetoresistive effect element and the shield core are electrically connected. I am using one. Further, a delay means for causing the generation of the sense current and the generation of the degaussing current at different timings (specifically, flowing the sense current after the degaussing current becomes 0) is provided in the reproduction circuit section. Providing a voltage-current conversion means for supplying a degaussing current control voltage to the degaussing current control voltage in the amplifier circuit of the reproducing circuit section and outputting the degaussing current as a degaussing current supply means for the reproducing circuit section. A triangular wave generating means for gradually reducing the amplitude, an alternating current signal generating means, and a multiplying means for multiplying the output signals from the triangular wave generating means and the alternating current signal generating means are provided.

Therefore, stabilization (demagnetization) of the magnetic characteristics of the shield core at the time of reproduction is possible only by externally attaching several parts for parameter setting to the recording / reproducing IC so as to satisfy the required demagnetization condition. Become.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing the configuration of an embodiment of a magnetoresistive head recording / reproducing circuit according to the present invention.

FIG. 2 is a block circuit diagram showing an essential part of the embodiment.

FIG. 3 is a block circuit diagram for explaining a specific example of a configuration of an amplifier circuit 31 of the one embodiment.

FIG. 4 is an MR of the magnetoresistive head device according to the embodiment.
FIG. 6 is a waveform chart for explaining an example of a current supplied to the head.

FIG. 5 is an MR of the magnetoresistive head device of the embodiment.
It is a wave form diagram which shows the other example of the electric current supplied to a head.

FIG. 6 is a block circuit diagram for explaining a specific example of the degaussing current control circuit of the one embodiment.

FIG. 7 is a perspective view showing a schematic configuration of a specific example of a shield type MR head used in the embodiment.

FIG. 8 is a sectional view showing a schematic configuration of a specific example of the MR inductive head used in the embodiment.

FIG. 9 is a perspective view showing a schematic configuration of another specific example of the shield type MR head used in the one embodiment.

FIG. 10 is a sectional view showing a schematic configuration of another specific example of the MR inductive head used in the one embodiment.

FIG. 11 is a block circuit diagram showing a schematic configuration of a recording / reproducing circuit for a magnetoresistive head using a conventional grounded-emitter amplifier circuit.

FIG. 12 is a block circuit diagram showing an example of a grounded-emitter amplifier circuit used in a conventional magnetoresistive head recording / reproducing circuit.

FIG. 13 is a block circuit diagram showing a schematic configuration of another embodiment of the magnetoresistive head recording / reproducing circuit according to the present invention.

FIG. 14 is a block circuit diagram showing an example of a grounded-emitter amplifier circuit used in the embodiment of FIG.

FIG. 15 is a perspective view showing a schematic configuration of a specific example of a shield type MR head used in a conventional magnetoresistive head device.

FIG. 16 is a cross-sectional view showing a schematic configuration of a specific example of an MR inductive head used in a conventional magnetoresistive head device.

FIG. 17 is a block circuit diagram showing an example of a conventional magnetoresistive head recording / reproducing circuit.

FIG. 18 is a block circuit diagram showing an example of a grounded base amplifier circuit used in a conventional magnetoresistive head recording / reproducing circuit.

[Explanation of symbols]

 MR element 2, 3 Shield core 2a, 2b Magnetic film 2c Nonmagnetic film 4 Bias conductor 5a .... Non-magnetic conductors 5b, 5c ... Electrodes 6 ... Magnetic core 7 ... Head winding 10, 10 '... MR head 22 ... Mode control circuit 27: Sense current control circuit 28: Demagnetization current control circuit 29: Delay circuit 31, 41: Amplifier circuit

Claims (5)

[Claims] 1. A magnetoresistive head including a recording circuit section for supplying a recording signal to the magnetoresistive head and a reproducing circuit section for taking out a reproduced signal from the magnetoresistive head. In the recording / reproducing circuit for use, the reproducing circuit section extracts the resistance change of the magnetoresistive effect element as a voltage through the amplifier circuit connected to the magnetoresistive effect element of the magnetoresistive effect head and the amplifier circuit. And a degaussing current supply means for supplying an alternating current with a gradually decreasing amplitude for degaussing to the magnetoresistive effect element via the amplifier circuit. A magnetoresistive head recording / reproducing circuit. 2. The magnetoresistive head has a magnetoresistive effect element and a shield core covering the magnetoresistive effect element, and the magnetoresistive effect element and the shield core are electrically connected to each other. The recording / reproducing circuit for a magnetoresistive head according to claim 1, wherein: 3. The magnetoresistive device according to claim 1 or 2, wherein delay means for causing the generation of the sense current and the generation of the degaussing current at mutually different timings is provided in the reproduction circuit section. Recording / playback circuit for effect type head. 4. A voltage-current converting means for supplying a degaussing current control voltage to the degaussing current control voltage and converting the degaussing current to output the degaussing current is provided in the amplifier circuit of the reproducing circuit section. A recording / reproducing circuit for the magnetoresistive head described. 5. The degaussing current supply means of the reproducing circuit section comprises:
It has a triangular wave generating means for gradually reducing the amplitude, an alternating current signal generating means, and a multiplying means for multiplying the respective output signals from these triangular wave generating means and alternating current signal generating means. A recording / reproducing circuit for a magnetoresistive effect head according to item 1, 2, 3 or 4.