JPH0438705A - Multi-track reproduction circuit - Google Patents

Abstract

PURPOSE:To offer the multi-track reproduction circuit of a very small circuit scale by giving a bias magnetic field to each closed magnetic circuit of a magnetic reluctance element to be common to plural closed magnetic circuits formed of each magnetic field of plural tracks on a magnetic tape. CONSTITUTION:The reproducing magnetic field of a first track, a second track, a third track, and a fourth track on the magnetic tape form the closed magnetic circuits corresponding to each track by each yoke 21, 22, 23, and 24, parts overlapping each yoke of the magnetic reluctance element 10 common to each track, and a base board 20. The parts overlapping each yoke of the magnetic reluctance element 10 convert the reproducing magnetic field of each track into electric resistance. Here, in the case that, for instance, the reproduced signal of the third track is obtained, a first current value is supplied to a bias conductor 13 corresponding to the third track. The current value to generate the magnetic field Hb is selected as the first current value. A second current value to generate the magnetic field Hs at which sensitivity becomes minimum is supplied to the other bias conductors 11, 12, and 14.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a multi-track reproducing circuit using a magnetoresistive element in a recording and reproducing apparatus that records and reproduces digital signals such as audio signals using a multi-track recording and reproducing method. It is something.

2. Description of the Related Art In recent years, devices that perform high-density digital magnetic recording, such as DAT (digital audio tape recorders), have been commercialized. In such devices, a multi-track recording/reproducing method is adopted to realize high-density recording.

As an example of a reproducing head realizing a multi-track recording/reproducing system, FIG. 6 is an enlarged perspective view showing an example of the structure of a four-track multi-track reproducing head using a magnetoresistive element.

In FIG. 6, reference numerals 15, 16, 17 and 18 are magnetoresistive elements for reproducing the magnetic fields of the first track, second track, third track and fourth track, respectively. Also 11, 12.
13 and 14 are magnetoresistive elements 15, 16, and 17, respectively.
and a bias conductor that provides a bias magnetic field to 18.

20 is a substrate made of Mn-Zn ferrite or the like; 21, 22, 23 and 24 are magnetoresistive elements 15, 16, . This is a yoke made of a Ni-Fe alloy, etc., for guiding the wires to 17 and 18.

FIG. 5 shows a block diagram of a conventional multi-track playback circuit constructed using the head shown in FIG. 6.

In FIG. 5, 50 surrounded by a broken line is the head shown in FIG. 6, and the other parts are peripheral circuits. 11.12 inside the multi-track playback head 50. 13,
14, 15, 18, 17, and 18 are the same as in FIG. 6, so their explanation will be omitted.

51 is a bias current source that provides a constant bias current to the bias conductors 11 to 14, 3 is a sense current source that provides a constant current to the magnetoresistive elements 15 to 18, 4 is a coupling capacitor for DC cut, and 52 is a magnetoresistive element. Element 15~
18 is a selection circuit for selecting the output, 5 is an output terminal for a reproduced signal, and 6 is a common terminal.

Next, the operation will be explained with reference to FIGS. 5 and 6. Consider the case of reproducing a recorded magnetic tape (not shown). The reproducing magnetic field of the first track, second track, third track, and fourth track on the magnetic tape is generated by the yokes 21, 22, 23, and 24, and the magnetoresistive element 1, respectively.
5. 16. 17 and 18 and the substrate 20 form a closed magnetic path corresponding to each track. Magnetoresistive elements 15 to 18 in each closed magnetic path convert the reproduction magnetic field of each track into electrical resistance.

FIG. 3 shows an example of the characteristics of the electrical resistance of a magnetoresistive element against a magnetic field. In order to achieve efficient conversion with little distortion, a constant magnetic field H is required so that the operation occurs at the center of the region where the resistance change is linear with respect to the magnetic field change, that is, at point (a) in Figure 3.
Just give b.

Therefore, the bias current source 51 supplies a constant current called a bias current to the bias conductors 11 to 14 so that the bias conductors 11 to 14 generate Hb.

On the other hand, changes in resistance of the magnetoresistive elements 15 to 18 are output as voltage changes by applying a constant current from the sense current source 3. Each voltage change is connected to the coupling capacitor 4
After the DC component is cut off, the selection circuit 52 selects the playback signal of the track required at that time, and outputs it from the output terminal 5.

Problems to be Solved by the Invention However, the above configuration requires a selection circuit for selecting a reproduced signal, and also requires coupling capacitors for the number of tracks, resulting in an increase in circuit scale.

In view of the above problems, it is an object of the present invention to provide a multi-track reproduction circuit with a very small circuit scale.

Means for Solving the Problems In order to achieve the above object, the multi-track reproducing circuit of the present invention includes a magnetoresistive element common to a plurality of closed magnetic paths formed by the respective magnetic fields of a plurality of recording tracks on a magnetic tape. A first current value is supplied to a plurality of bias conductors that apply a bias magnetic field to each closed magnetic path of the magnetoresistive element, and a bias conductor corresponding to a predetermined closed magnetic path, and a second current value is supplied to other bias conductors. and a current source circuit that supplies a current value of 1, and is characterized in that a resistance change corresponding to a change in the magnetic field forming the predetermined closed magnetic path is obtained as an output of the magnetoresistive element.

Function: With the above-described configuration of the multi-track reproducing circuit of the present invention, the portion of the magnetoresistive element corresponding to each closed magnetic path converts the reproducing magnetic field of each track into electric resistance.

The magnetic field-resistance conversion characteristics of the portion of the magnetoresistive element corresponding to each closed magnetic path are determined by the first or second current value supplied to the bias conductor by the current source circuit.

Embodiment FIG. 2 is an enlarged perspective view showing an example of the structure of a four-track multi-track reproducing head for realizing a multi-track reproducing circuit according to an embodiment of the present invention.

11 in Figure 2. 12. 13. 14. 20. 2
1.degree. 23 and 24 are the same as those in the conventional example shown in FIG. 6, so their explanation will be omitted. 10 is one magnetoresistive element common to the first track, the second track, the third track, and the fourth track.

FIG. 1 is a block diagram showing a multi-track reproducing circuit according to an embodiment of the present invention, and is an example of a four-track circuit constructed using the reproducing head shown in FIG.

In FIG. 1, 1 surrounded by a broken line is a multi-track reproducing head, 2 is a current source circuit that applies a first or second current value to the bias conductors 11 to 14, and 3 is a current source circuit that applies a constant current to the magnetoresistive element 10. 4 is a coupling capacitor, 5 is a reproduction signal output terminal, and 6 is a common terminal.

The operation will be described below with reference to FIGS. 1 and 2.

First, consider the case of playing back a recorded magnetic tape (not shown).
The reproduction magnetic field of the third track, the third track, and the fourth track is generated by the yokes 21, 22, 23, and 24, the portion where the magnetoresistive element 10 common to each track overlaps each yoke, and the substrate 20. A corresponding closed magnetic path is formed.

The portion of the magnetoresistive element 10 that overlaps each yoke converts the reproduction magnetic field of each track into electrical resistance.

Here, for example, when obtaining the reproduction signal of the third track,
A first current value is applied to the bias conductor 13 corresponding to the third track. As the first current value, a current value that generates a magnetic field Hb with the operating point at point (a) in FIG. 3 is selected. For the other bias conductors 11, 12, and 14, a second current value is supplied that generates a magnetic field Hs whose operating point is the operating point at which the sensitivity is minimum, for example, the point in FIG. 3(b). As a result, only the portion of the magnetoresistive element 10 constituting the closed magnetic path corresponding to the third track becomes operational. That is, the magnetoresistive element 10 converts only the magnetic field of the third track into a change in resistance.

The resistance change of the magnetoresistive element 10 is converted into a voltage change by a constant current from the sense current source 3, and the voltage change is outputted from the output terminal 5 after the direct current component is cut by the coupling capacitor 4.

Here, the second current value of the current source circuit is as shown in Fig. 3 (
It is not limited to point b), but may be any value as long as it is an operating point at which the sensitivity of the magnetoresistive element becomes small.

FIG. 4 is a block diagram showing a multi-track reproduction circuit according to another embodiment of the present invention, in which instead of one magnetoresistive element 10 common to each closed magnetic path in FIG. Magnetoresistive elements 15 to 18 are connected in series.

The operation is exactly the same as in FIG.

Effects of the Invention As described above, according to the multi-track playback circuit of the present invention, there is no need for a selection circuit and only one coupling capacitor is required regardless of the number of tracks, so the scale of the peripheral circuitry can be significantly reduced. This contributes to the miniaturization of devices and is extremely useful in practice.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a multi-track reproducing circuit according to an embodiment of the present invention, FIG. 2 is an enlarged perspective view showing an example of the structure of the multi-track reproducing head in FIG. 1, and FIG.
FIG. 4 is a block diagram of a multi-track reproducing circuit according to another embodiment of the present invention, and FIG. 5 is a block diagram of a conventional multi-track reproducing circuit. 6 is an enlarged perspective view showing an example of the structure of the multi-track reproducing head shown in FIG. 5. DESCRIPTION OF SYMBOLS 1... Multi-track reproduction head, 2... Current source circuit, 10... Magnetoresistive element, 11-14
...Bias conductor.

Claims (1)

[Claims] A magnetoresistive element that is common to a plurality of closed magnetic paths formed by the magnetic fields of each of a plurality of recording tracks on a magnetic tape, and a plurality of magnetoresistive elements that apply a bias magnetic field to each closed magnetic path of the magnetoresistive elements. It is composed of a bias conductor and a current source circuit that supplies a first current value to the bias conductor corresponding to a predetermined closed magnetic path and a second current value to the other bias conductors, and the current source circuit supplies the magnetoresistive element. A multi-track reproducing circuit characterized in that a resistance change corresponding to a change in a magnetic field forming the predetermined closed magnetic path is obtained as an output.