JPH1011706A - Drive circuit for inductive magnetic head - Google Patents

Abstract

(57) Abstract: It is difficult to shorten the polarity reversal time Tr by reducing the inductance of a magnetic head, so that it has been difficult to support high-density and high-frequency magnetic recording. SOLUTION: In a drive circuit of an induction type magnetic head 10 having three coil terminals 12, 13, 14, one of the three coil terminals 12, 13, 14 is shared by a reproducing system and a recording system. Then, the common coil terminal 13 and each of the remaining two coil terminals 12, 14 are paired to form two coils having different inductances,
A coil having a large inductance is connected to the reproducing circuit 21 and a coil having a small inductance is connected to the recording circuit 22, and the coil terminal 12 other than the common coil terminal 13 to which the reproducing circuit 21 is connected is connected to the recording circuit 2
2 and a dummy circuit 23 having a capacitance equivalent to a capacitance component are connected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive circuit for an induction type magnetic head, and more particularly to an induction type magnetic head having a continuous coil having three coil terminals and recording and reproducing information by a magnetic flux change caused by electromagnetic induction. The present invention relates to a head driving circuit.

[0002]

2. Description of the Related Art In data processing, a magnetic disk device such as a hard disk drive (HDD) is used because of the necessity of high-speed data processing and a large amount of data processing. Such a magnetic disk device is provided with a magnetic head for recording and reproducing information. The magnetic head is
A process of magnetically recording information on a magnetic medium or reading and reproducing the recorded information magnetically is performed by a magnetic flux change due to electromagnetic induction.

Conventionally, as a magnetic head used in a magnetic disk drive, there is an induction type magnetic head which records and reproduces information by a change in magnetic flux due to electromagnetic induction. For example, a ferrite head and a metal-in-gap (MIG) type are available.
Magnetic heads and thin-film magnetic heads are known.

FIG. 13 is a schematic configuration diagram showing a configuration of a conventional induction type magnetic head and its driving circuit. 13, the magnetic head 100 includes one coil 101, and the drive circuit 200 includes a reproducing circuit 201 and a recording circuit 202 commonly connected to the coil 101. The reproduction circuit 201 reads out the current induced in the coil 101 and reproduces recorded information. Recording circuit 202
Supplies information in the forward and reverse directions to the coil 101 in accordance with the recording data to record information.

Next, the operation of the recording circuit 202 in the conventional driving circuit having the above configuration will be described with reference to the operation explanatory diagram of FIG. First, when the recording circuit 202 receives a control signal generated based on recording data, the recording circuit 202
01 is supplied with the recording current I. It should be noted that the control signal in FIG. 14 is NR for performing code conversion every time recording data is input.
The case of the ZI (non return to zero inverted) recording method is shown.

[0006] The magnetic medium is magnetized by a magnetic field generated by a recording current. When the magnitude of the recording current I is small and the magnetic medium is in an unsaturated state, it is in an insufficient magnetization state (A in the figure), and the recording current I is a medium magnetization current sufficient to magnetically saturate the magnetic medium (in the figure). I +, I indicated by broken lines
When the value exceeds-) (C in the figure), the magnetic medium becomes in a sufficiently magnetized state (B in the figure), whereby information is recorded.

Normally, the recording current I flowing through the coil to excite the magnetic head is controlled based on a fixed period of the reversal interval T. When the recording current I exceeds the medium magnetization current value from the input of the control signal, the medium magnetization is reduced. Until the operation is performed, the polarity inversion time Tr
Delay time. The polarity reversal time Tr depends on the circuit characteristics of the recording circuit 202 and the inductance of the magnetic head 101. When the ratio with respect to the reversal interval T increases, for example, the unsaturated magnetization portion in the medium (A in FIG. 14)
Are magnetized in the opposite direction (D in FIG. 14) by the magnetic field in the opposite direction of the adjacent saturated magnetization portion (B in FIG. 14), and excellent due to a phenomenon such as a shift of the magnetization transition point (C in FIG. 14). It is difficult to obtain a magnetized state. For this reason, it is usually desired that the polarity inversion time Tr is 以下 or less of the inversion interval T. In particular, when performing high-frequency recording, the inversion interval T becomes shorter. Become.

In magnetic disk drives, high-frequency recording at high density is desired. For example, the recording density is 6000 TPI in track density and 134 KFCI in linear recording density.
High density is required, and the recording frequency is 50 MHz
The above high frequency recording is desired. In high-frequency recording of 50 MHz or more, the reversal interval T of the recording current is 10 ns, so that a polarity reversal time Tr of 5 ns or less is required. However, for example, using currently available recording circuits,
In order to set the polarity reversal time Tr to 5 ns in a coil magnetic head having 42 turns, the inductance of the magnetic head needs to be about 0.6 μH.

However, a metal-in-gap (MIG) magnetic head having 42 turns has an inductance of about 1.8 μH and a polarity inversion time Tr of 5 ns.
It is difficult to: Therefore, the polarity inversion time T
To reduce r, it is necessary to reduce the inductance of the magnetic head. The magnitude of the inductance of the magnetic head depends on the number of turns of the coil and the cross-sectional area of the magnetic material in the part of the number of turns of the coil. However, in the MIG head, the magnetic head circuit is formed by machining ferrite, so that There is a limit to the reduction of body cross section. Therefore, it is necessary to reduce the number of coil turns in order to reduce the inductance of the magnetic head.

[0010]

However, in the above-described conventional inductive magnetic head drive circuit, recording of information on a magnetic medium and reproduction of recorded information are performed by the same coil 1.
01, the reproduction output level decreases when the number of turns of the coil 101 is reduced. Therefore, it is difficult to shorten the polarity inversion time Tr by reducing the inductance of the magnetic head.
There is a problem that it is difficult to cope with high-density and high-frequency magnetic recording.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to be able to cope with high-density, high-frequency magnetic recording while ensuring a sufficiently large reproduction output level. An object of the present invention is to provide a drive circuit for an inductive magnetic head.

[0012]

A drive circuit according to the present invention is a drive circuit for an induction type magnetic head which includes one continuous coil having three coil terminals and records and reproduces information by a magnetic flux change caused by electromagnetic induction. A reproduction circuit connected to one coil terminal pair formed by two of the three coil terminals and reproducing a signal from a reproduction coil formed by a coil part between the one coil terminal pair; ,
Two of the three coil terminals sharing one of the coil terminal pairs of the one coil terminal pair are connected to another coil terminal pair formed by the two coil terminals, and a coil portion between the other coil terminal pairs is formed. And a load circuit connected to the other coil terminal of the one coil terminal pair and having a capacitance equivalent to a capacitance component of the recording circuit. It has a configuration.

In the driving circuit for an induction type magnetic head having the above-mentioned configuration, first, in the induction type magnetic head, one of three coil terminals of one continuous coil is made common, and this one coil terminal is connected to another coil terminal. By forming two coil terminal pairs between the two coil terminals, each coil portion between the two coil terminal pairs is defined as a reproduction coil and a recording coil. Then, the reproducing circuit reads the information recorded on the magnetic medium by inputting a signal from the reproducing coil, and the recording circuit writes the information on the magnetic medium by supplying the recording current in the normal and reverse directions only to the recording coil.

That is, reproduction and recording can be realized by different coils. Thereby, a reproduction coil having a large inductance and a recording coil having a small inductance can be configured. As a result, a sufficiently large reproduction output level can be ensured during reproduction, and the polarity inversion time T during recording.
r can be set shorter. In addition, the load circuit connected to the other coil terminal of the reproduction coil has a capacitance equivalent to the capacitance component of the recording circuit connected to one coil terminal of the reproduction coil, so that the two input terminals of the reproduction circuit are connected. The capacity load added to each is balanced.

Another drive circuit according to the present invention is a drive circuit for a plurality of inductive magnetic heads, each of which includes one continuous coil having three coil terminals and records and reproduces information by a magnetic flux change caused by electromagnetic induction. A plurality of reproduction circuits connected to one coil terminal pair formed by two of the three coil terminals and reproducing a signal from a reproduction coil formed by a coil portion between the one coil terminal pair; , One of the coil terminal pairs having a common coil terminal.
A plurality of coil terminals connected to another coil terminal pair formed by two of the coil terminals and supplying a recording current in the normal and reverse directions only to a recording coil formed by a coil unit between the other coil terminals; A recording circuit, and a single load circuit commonly connected to the other coil terminal of the one coil terminal pair and having a capacitance equivalent to a capacitance component of the recording circuit for each of the plurality of inductive magnetic heads. It is provided with a configuration.

In the driving circuit for a plurality of inductive magnetic heads having the above configuration, the load circuit connected to the other coil terminal of the reproducing coil is equivalent to the capacitance component of the recording circuit connected to one coil terminal of the reproducing coil. By having a large capacity,
The capacity connected to each of the two input terminals of the reproduction circuit is balanced. In addition, the load circuit is provided in common for each of the plurality of inductive magnetic heads, thereby simplifying the circuit configuration.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram showing one embodiment of the present invention. In FIG. 1, a magnetic head 10 includes one coil 11, and a driving circuit 20 includes a reproducing circuit 21 and a recording circuit 2 connected to the coil 11.
2 is provided. One coil 11 has three terminals: end terminals 12 and 13 at both ends and an intermediate terminal 14. All coils formed between the terminals of the end terminals 12 and 13 constitute a reproduction coil. And the end terminals 12, 1
Reference numeral 3 denotes two circuit input terminals 21a and 21b of the reproduction circuit 21.
It is connected to the.

The coil 11 is connected to the intermediate terminal 14
The first coil 15 is formed between one end terminal 12 and the intermediate terminal 14, and the second coil 16 is formed between the other end terminal 13 and the intermediate terminal 14. ing. One of the first and second coils 15 and 16, in this example, the second coil 16 constitutes a recording coil. The end terminal 13 and the intermediate terminal 14 are connected to two circuit output terminals 22a and 22b of the recording circuit 22.

The first coil 15 is a recording coil,
It goes without saying that the end terminal 12 and the intermediate terminal 14 may be connected to the two input terminals 22a and 22b of the recording circuit 22. Further, the position of the intermediate terminal 14 in the entire coil 11 can be set arbitrarily. In particular,
The position of the intermediate terminal 14 is set such that the inductance of the recording coil falls within the polarity inversion time Tr that can realize the frequency at which magnetic recording is performed.

Further, of the end terminals 12 and 13 to which the reproducing circuit 21 is connected, the terminal to which the recording circuit 22 is not connected, that is, the end terminal 12 has, for example, the same circuit configuration as the recording circuit 22. The dummy circuit 23 is connected to the other end terminal 13.
Is connected as a load circuit having a capacitance equivalent to the capacitance component of the recording circuit 22 connected to the recording circuit 22. Thus, the drive circuit 20 for driving the magnetic head 10 is configured.

FIG. 2 is a circuit diagram showing an example of the circuit configuration of the recording circuit 22. In FIG. 2, transistors Q1,
The emitters of Q2 are connected in common and are further grounded via a resistor R. Each collector of the transistors Q1 and Q2 is connected to two circuit output terminals 22a and 22b of the recording circuit 22.
, And the respective bases are respectively connected to two output terminals of a buffer 24 that derives outputs of phases opposite to each other. Two input terminals of the buffer 24 are connected to the recording circuit 22.
Are connected to the two circuit input terminals 25a and 25b, respectively.

The two output terminals 22a, 22 of the recording circuit 22
As described above, the second coil (recording coil) 16 of the coil 11 is connected to b. Transistor Q1,
Each collector of Q2 is connected to each emitter of transistors Q3 and Q4. The collectors of the transistors Q3 and Q4 are connected to the power supply Vcc, and the bases are respectively connected to two output terminals of a buffer 26 that derive outputs of opposite phases. The two inputs of buffer 26 are:
The recording circuit 22 is connected to two circuit inputs 25a and 25b, respectively.

In the recording circuit 22 having the above configuration, when the transistors Q1 and Q4 are turned on based on the recording data applied to the circuit input terminals 25a and 25b, the second coil (recording coil) 16 When a recording current flows from the output terminal 22b side to the circuit output terminal 22a side (from the right side to the left side in the drawing) and the transistors Q2 and Q3 are turned on, the circuit output from the circuit output terminal 22a side to the second coil 16 is made. Information is recorded by a recording current flowing to the end 22b side (from the left side to the right side in the figure).

In this embodiment, as the dummy circuit 23,
The one having the same circuit configuration as the recording circuit 22 is used. However, since no input of recording data or the like is given to the dummy circuit 23, the dummy circuit 23
Is not performed. The operation of the dummy circuit 23 will be described later in detail.

Here, the operation at the time of reproduction in the drive circuit according to the present embodiment will be described with reference to the circuit diagram of FIG. In FIG. 3, at the time of reproduction, all the coils of the coil 11 become reproduction coils, and the read circuit Ir measures the read current Ir induced in the coil 11 in accordance with the record information of the magnetic medium (not shown). Perform playback. By setting the total inductance Lh at the time of reading of the coil 11 to, for example, about 0.95 μH, it is possible to cope with a magnetic disk device having a maximum recording frequency of 50 MHz or more, and a predetermined reproduction output level can be secured.

Next, the operation at the time of recording will be described with reference to the circuit diagram of FIG. In FIG. 4, at the time of recording, only the second coil 16 of the coil 11 is used as a recording coil. Thereby, the inductance L2 at the time of recording can be made lower than the inductance Lh at the time of reproduction. For example, if the intermediate terminal 14 is set to a substantially middle portion of the coil 11, the inductance L of the coil is in proportion to the square of the number of turns N, so that the inductance L2 at the time of recording is approximately 1/4 of the inductance Lh at the time of reproduction. Become.

Then, the recording circuit 22 supplies the second coil 16 with a recording current of Iw1 or Iw2 in accordance with the recording data. The reverse recording current Iw flowing through the second coil 16
Since the directions of 1 and Iw2 are the directions of the recording current output from the recording circuit 22, there is no need to switch the recording current. Further, since there is only one recording coil, there is no need to switch and supply the recording current to the two recording coils. In addition, about the 1st coil 15 in the coil 11, the end terminal 12
Is not connected to the recording circuit 22 and is not used during recording.

FIG. 5 is an explanatory diagram of the operation of the recording circuit 22. In FIG. 5, when the recording circuit 22 receives a control signal generated based on the recording data, it supplies a recording current I to the second coil 16 of the coil 11. The control signal in FIG. 5 shows the case of the NRZI recording system in which code conversion is performed every time recording data is input.
It is represented by w1, and the negative direction is represented by Iw2. The positive and negative directions are set for convenience, and can be expressed in the opposite direction.

The magnetic medium is magnetized by a magnetic field generated by the recording current I. The recording current I according to the change of the control signal
Is reversed, the recording current I changes with a time constant corresponding to the magnitude of the inductance L2 of the second coil (recording coil) 16. The recording current I is a medium magnetization current sufficient to magnetically saturate the magnetic medium (I shown by a broken line in the drawing).
When the value exceeds (+, I-), the magnetic medium is sufficiently magnetized, thereby recording information.

At this time, the recording current I flowing through the second coil 16 to excite the magnetic head 10 is controlled based on a constant period of the reversal interval T. This is performed after a delay time of the polarity reversal time Tr until the medium magnetization is performed beyond the current value. The polarity reversal time Tr depends on the circuit characteristics of the recording circuit 22 and the inductance of the magnetic head 10. By setting the inductance L2 of the second coil (recording coil) 16 to, for example, 0.3 μH or less, the normal magnetic recording is performed. A polarity inversion time Tr of 1/2 or less of a desired inversion period T
The maximum recording frequency is 50 MHz
The above-described magnetic disk device can be supported.

When the reversal interval T is shortened by high-frequency recording and the ratio of the polarity reversal time Tr to the reversal interval T is increased, the reverse magnetization due to the magnetic field in the opposite direction from the adjacent saturated magnetization portion of the medium to the unsaturated magnetization portion in the medium. A phenomenon such as deviation of the magnetization transition point occurs due to a phenomenon such as directional magnetization. However, a phenomenon such as a shift of the magnetization transition point is reduced by shortening the polarity inversion time Tr due to a decrease in the inductance L2 of the second coil (recording coil) 16. Can be reduced.

In the recording circuit 22, the recording current I
Since a current of 10 mA or more flows as
Large transistors are used as the transistors Q1 to Q4 constituting the second transistor. Since one circuit output terminal 22 b of the recording circuit 22 is commonly connected to one circuit input terminal 21 b of the reproducing circuit 21 and one terminal 13 of the coil 11, one terminal of the reproducing circuit 21 A capacitive load due to the capacitive component of the recording circuit 22 is applied between only the circuit input terminal 21b and the ground.

One of the circuit input terminals 21 of the reproducing circuit 21
As the capacitance component of the recording circuit 22 added only to b,
The main parasitic capacitance of the transistor Q2 interposed between the circuit output terminal 22b and the ground. in this way,
Since a capacitive load is applied only to one circuit input terminal 21b of the reproduction circuit 21, ground noise is injected into only one end terminal 13 side of the coil 11 through this capacitive load, and particularly, in the middle region. This will increase the noise level.

FIG. 6 shows the noise characteristics of the reproducing circuit 21 at this time when there is no signal. In FIG. 6, the horizontal axis is frequency,
The vertical axis represents the output level. As is apparent from this noise characteristic diagram, one circuit input terminal 21 of the reproduction circuit 21
It can be seen that when a capacitive load is added only to b, the noise level at the peak of the middle range is boosted to about 4.7 times the noise level of the low range. As a result, S /
N will worsen.

On the other hand, in the present embodiment, the coil 1
A configuration is adopted in which a dummy circuit 23 having the same circuit configuration as the recording circuit 22 is connected to the other end terminal 12 of the recording medium 22.
As a result, the same capacitive load as that of the one circuit input terminal 21b is applied to the other circuit input terminal 22a of the reproduction circuit 21. Thereby, the reproduction circuit 21
The ground noise is commonly input to the two circuit input terminals 22a and 22b. Normally, since the reproduction circuit 21 is configured using a differential amplifier, ground noise commonly input to the circuit input terminals 22a and 22b does not appear in the output. As a result, it is possible to suppress an increase in the noise level particularly in the middle band.

FIG. 7 shows the noise characteristic of the reproducing circuit 21 when there is no signal at this time. In FIG. 7, the horizontal axis is frequency,
The vertical axis represents the output level. As is clear from this noise characteristic diagram, the other circuit input terminal 22 of the reproduction circuit 21
It can be seen that the noise level at the peak of the middle band can be suppressed to about three times the noise level of the low band by adding the same capacitive load to the circuit input terminal 21b side as for a.

The driving circuit including the reproducing circuit 21 and the recording circuit 22 is usually integrated into a plurality of ICs corresponding to the case where there are a plurality of magnetic heads 10 (the case of multi-channel). From this, when all the channels are not used, there is naturally a drive circuit that is not used. Therefore, in such a usage form, a vacant recording circuit can be used without specially manufacturing the dummy circuit 23 as a separate circuit. In that case, the present embodiment can be realized only by slightly changing the wiring pattern.

In this embodiment, the recording circuit 2 is used as a load circuit connected to the other end terminal 12 of the coil 11.
The dummy circuit 23 having the same circuit configuration as that of the coil 11 is used, but as shown in FIG.
It is also possible to connect a capacitor C having a capacitance equivalent to the capacitance component (mainly the parasitic capacitance of the transistor Q2) of the recording circuit 22 connected to 3. According to this, in the case of a single channel, since only one capacitor is required as a newly added element, it can be realized with a simple circuit configuration.

Further, one circuit input terminal 2 of the reproduction circuit 21
Since the parasitic capacitance of the transistor Q2 interposed between the circuit output terminal 22b and the ground is mainly used as the capacitance component of the recording circuit 22 added only to 1b,
As shown in FIG. 9, a transistor having a parasitic capacitance equivalent to the capacitance component of the recording circuit 22 connected to one end terminal 13 of the coil 11, that is, a transistor Q10 having the same size as the transistor Q2 can be connected. It is. As described above, by using a transistor, a driver circuit can be easily manufactured by the same process.

FIG. 10 shows a case where a plurality of magnetic heads, for example, two
FIG. 11 is a schematic configuration diagram showing another embodiment of the present invention applied to the case of two (two channels). In FIG. 9, the first and second
The magnetic heads 30 and 40 of the channels have one coil 31 and 41, respectively. On the other hand, the drive circuit 50 includes reproduction circuits 51 and 52 and recording circuits 53 and 54 connected to the coils 31 and 41. The coil 31 has three terminals: end terminals 32 and 33 at both ends and an intermediate terminal 34.

In this coil 31, the end terminals 32,
All coils formed between the 33 terminals constitute a reproduction coil, and the end terminals 32 and 33 are connected to two circuit input terminals 51 a and 51 b of the reproduction circuit 51. The coil 31 is divided into two coil portions by an intermediate terminal 34, and a first coil 3 is provided between one end terminal 32 and the intermediate terminal 34.
5 and a second coil 36 is formed between the other end terminal 33 and the intermediate terminal 34. Then, for example, the second coil 36 constitutes a recording coil, and the end terminal 33 and the intermediate terminal 34 are connected to two circuit output terminals 53 a of the recording circuit 53.
53b.

Similarly to the coil 31, the coil 41 has three terminals of end terminals 42 and 43 at both ends and an intermediate terminal 44. In the coil 41, the end terminals 42, 4
All the coils formed between the terminals 3 constitute a reproduction coil,
The end terminals 42 and 43 are connected to two circuit input terminals 52 a and 52 b of the reproduction circuit 52. The coil 41 is divided into two coil portions by an intermediate terminal 44, a first coil 45 is formed between one end terminal 42 and the intermediate terminal 44, and a first coil 45 is formed between the other end terminal 43 and the intermediate terminal 44. Form a second coil 46. Then, for example, the second coil 46 constitutes a recording coil, and the end terminal 43 and the intermediate terminal 44 are connected to two circuit output terminals 54 a and 54 of the recording circuit 54.
b.

Of the end terminals 32 and 33 to which the reproduction circuit 51 is connected, the terminal to which the recording circuit 53 is not connected, that is, the end terminal 32 has the same circuit configuration as the recording circuit 53, for example. The dummy circuit 55 is connected to the other end terminal 33.
Is connected as a load circuit having a capacitance equivalent to the capacitance component of the recording circuit 53 connected to the recording circuit 53. This dummy circuit 55
Is also connected to the terminal on the side to which the recording circuit 54 is not connected, that is, the end terminal 42, of the end terminals 42 and 43 to which the reproduction circuit 52 is connected.

That is, a single dummy circuit 55 is commonly connected to the end terminal 32 of the coil 31 and the end terminal 42 of the coil 41. The dummy circuit 55 has the same circuit configuration as the recording circuits 53 and 54, as in the previous embodiment.
A capacitor having a capacitance equivalent to the capacitance component of 54 or a transistor having a parasitic capacitance equivalent to the capacitance component of the recording circuits 53 and 54 is used.

As described above, by adopting a configuration in which the dummy circuit 55 is provided in common for the two-channel reproduction circuits 51 and 52, only one dummy circuit 55 is required, and a minimum number of additional circuit elements are added. Therefore, with a simple circuit configuration, an increase in the noise level of the reproduction output due to the ground noise can be suppressed. In particular, the dummy circuit 5
As a fifth example, when using a vacant recording circuit among a plurality of recording circuits produced for a plurality of channels,
This is useful when only one recording circuit is free.

FIG. 11 is a perspective view showing an example of the configuration of the magnetic head. In the figure, the same parts as those in FIG. 1 are denoted by the same reference numerals. In FIG. 11, the magnetic head 10
A coil 11 is formed by winding a parallel wire around a core 17 made of a magnetic material such as ferrite which forms a magnetic circuit. In the gap 17 of the core 17, metal magnetic films (Fe-Ta-N) 19a and 19b having high magnetic permeability are provided.

The coil (parallel wire) 11
It is composed of two lines as shown in FIG.
One of the two lines (shown by a solid line in the figure) has a terminal a and a terminal b1, and the other line (shown by a broken line in the figure) has a terminal b2 and a terminal c. This parallel wire 11 is wound around a core 17, and as shown in FIG.
Assuming that the terminals a and c are the end terminals 12 and 13 in FIG.
It is possible to form a reproducing coil in which a wire of two lengths is wound.

When the terminals b1 and b2 of each line are connected to form the intermediate terminal 14 shown in FIG. 1, between the end terminal 12 and the intermediate terminal 14 and between the end terminal 13 and the intermediate terminal 14 In the above, the first and second coils 15 and 16 in which wires each having one length are wound can be formed.
Then, the second coil 16 is used as a recording coil. When the recording coil and the reproduction coil are compared, the ratio of the number of turns wound around the core 17 is approximately 1: 2, and the inductance L of the coil is proportional to the square of the number of turns N as described above. The inductance ratio is almost 1
/ 4.

[0049]

As described above, according to the present invention,
In a drive circuit for an induction type magnetic head having three coil terminals, one of the three coil terminals is shared by a reproducing system and a recording system, and this common coil terminal and each of the remaining two coil terminals are used. 2 with different inductance as a pair
One coil with a large inductance is connected to the reproduction circuit, and a coil with the small inductance is connected to the recording circuit.The other coil terminal, which is not the common coil terminal to which the reproduction circuit is connected, has the capacity of the recording circuit. By connecting a load circuit having a capacitance equivalent to the component, the capacitive load added to the two circuit input terminals of the reproduction circuit is balanced and is not affected by ground noise. Thus, it is possible to secure a sufficiently large reproduction output level while suppressing the rise of the magnetic head, and to cope with high-density and high-frequency magnetic head recording.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.

FIG. 2 is a circuit diagram illustrating an example of a circuit configuration of a recording circuit.

FIG. 3 is a circuit diagram of a reproduction system.

FIG. 4 is a circuit diagram of a recording system.

FIG. 5 is an explanatory diagram of an operation of the recording circuit.

FIG. 6 is a noise characteristic diagram of a reproduction circuit when a load circuit is not connected.

FIG. 7 is a noise characteristic diagram of a reproduction circuit when a load circuit is connected.

FIG. 8 is a schematic configuration diagram showing a modification of the embodiment.

FIG. 9 is a schematic configuration diagram showing another modification of the embodiment.

FIG. 10 is a schematic configuration diagram showing another embodiment of the present invention.

FIG. 11 is a perspective view showing an example of a configuration of a magnetic head.

FIG. 12 is a connection diagram of parallel lines forming a coil.

FIG. 13 is a schematic configuration diagram showing a conventional example.

FIG. 14 is a diagram illustrating the operation of a conventional example.

[Explanation of symbols]

10,30,40 Magnetic head 11,31,41
Coil 12, 13, 32, 33, 42, 43 End terminal 14, 34, 44 Intermediate terminal 20, 50 Driving circuit 21, 51, 52 Reproducing circuit 22, 53, 54 Recording circuit 23, 55 Dummy circuit

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor, Yasuo Sakaguchi 5200, Sangejiri, Kumagaya-shi, Saitama Hitachi Metals Co., Ltd. Materials Research Laboratory

Claims (8)

[Claims] 1. A driving circuit for an induction type magnetic head, comprising: a continuous coil having three coil terminals, for recording and reproducing information by a magnetic flux change caused by electromagnetic induction, wherein: A reproduction circuit connected to one coil terminal pair formed by the two coil terminals and reproducing a signal from a reproduction coil formed by a coil portion between the one coil terminal pair; and one of the one coil terminal pair Two of the three coil terminals having a common coil terminal are connected to another coil terminal pair formed by two coil terminals, and only the recording coil formed by the coil part between the other coil terminal pairs is forward / reverse. And a load circuit connected to the other coil terminal of the one coil terminal pair and having a capacitance equivalent to a capacitance component of the recording circuit. Drive circuit for an inductive magnetic head. 2. The drive circuit according to claim 1, wherein the load circuit is a dummy circuit having the same circuit configuration as the recording circuit. 3. The drive circuit according to claim 1, wherein the load circuit is a capacitor having a capacitance equivalent to a capacitance component of the recording circuit. 4. The drive circuit according to claim 1, wherein the load circuit is a transistor having a parasitic capacitance equivalent to a capacitance component of the recording circuit. 5. A drive circuit for a plurality of induction type magnetic heads, comprising a continuous coil having three coil terminals, and recording and reproducing information by a magnetic flux change due to electromagnetic induction, wherein: A plurality of reproduction circuits connected to one coil terminal pair formed by two of the coil terminals and reproducing signals from a reproduction coil formed by a coil portion between the one coil terminal pair; and the one coil terminal The recording coil is connected to another coil terminal pair formed by two of the three coil terminals having one of the pair of coil terminals in common, and formed by a coil portion between the other coil terminal pairs. A plurality of recording circuits for supplying a recording current only in the forward and reverse directions, and the plurality of inductive magnetic heads are connected in common to the other coil terminal of the one coil terminal pair and the recording is performed. And a single load circuit having a capacitance equivalent to a capacitance component of the circuit. 6. The drive circuit according to claim 5, wherein the load circuit is a dummy circuit having the same circuit configuration as the recording circuit. 7. The drive circuit according to claim 5, wherein the load circuit is a capacitor having a capacitance equivalent to a capacitance component of the recording circuit. 8. The drive circuit according to claim 5, wherein the load circuit is a transistor having a parasitic capacitance equivalent to a capacitance component of the recording circuit.