JPS61284819A - Magneto-resistance effect type reproducing head - Google Patents

Abstract

PURPOSE:To obtain a magneto-resistance effect type reproducing head preventing generation of a thermal noise, by making a sampling period of a sample holding circuit coincide with a period of a bias use high frequency current. CONSTITUTION:A high frequency current circuit is connected to a bias conductor, and also an output signal of a magneto-resistance effect element is divided into two, one is supplied to a differential amplifier 10, and the other is supplied to the differential amplifier 10 through a sample holding circuit 9. In this case, said signal is converted to a signal having an envelope by executing an operation by the sample holding circuit 9 and the differential circuit 10. By processing this signal by a detecting/rectifying circuit 11, an electric signal corresponding to an input magnetic field signal of an MR element 1 is obtained in an output terminal 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a magnetoresistive read head to which a bias magnetic field is applied.

[Background of the invention]

Conventionally, in order to use a magnetoresistive element with good linearity, a bias magnetic field is applied to the magnetoresistive element by passing a current through a conductor provided close to the magnetoresistive element, that is, a bias conductor. type playback heads are known (for example, Japanese Patent Laid-Open No. 51-112
320, JP-A-58-182125). However, such a configuration has a problem in that the reproduced signal waveform is distorted due to thermal noise generated in the magnetoresistive element.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetoresistive reproducing head which eliminates the problems of the prior art and prevents the generation of thermal noise.

[Summary of the invention]

The magnetoresistive effect is an interaction between a current passed through an element and magnetic spin, and is essentially different from a change in thermal resistance based on the interaction between electrons. Thermal noise is caused by the element temperature shifting as indicated by the arrow → in FIG. 5 as the temperature T1 changes to T2 due to tape sliding. In order to achieve the above object, the present invention is shown in FIG.

Paying attention to the fact that B, -A, = B2 - A2, set the bias magnetic field applied to the magnetoresistive element to a sufficiently large value. Point) By extracting the difference between Bl and B2 as a reproduced signal.

The feature is that it eliminates thermal noise.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a magnetoresistive reproducing head according to the present invention, in which 1 is a magnetoresistive element (hereinafter referred to as MR element), 2 is an insulator, 3 is a bias conductor, 4a and 4b are bias conductor connection terminals, 5a
, 5b is the MR element connection terminal.

6a, 6b, 6c, 6 (I is lead wire, 7
8 is a high frequency bias circuit, 8 is an MR element current circuit, 9 is a sample hold circuit, IO is a differential circuit, 11 is a detection rectifier circuit, and 12 is a reproduced signal output terminal.

In the figure, the bias conductor 3 is a connection terminal 4a.

In this embodiment, it is only necessary that the MR element be placed close to the MR element so that the magnetic field generated when a current is passed through 4b rotates the MR element 10 in the width direction (orthogonal direction to the connecting terminals 5a and 5blC). An MR element 1 is placed on a bias conductor 3 with an insulator 2 interposed therebetween.

The MR element 1 is connected to the MR element current circuit 8 in Fig. 2 (1a).
As shown in FIG.
, 5a and a grounded lead 6b. Further, the lead wire 6d has a sample hold circuit 9. Differential circuit 10. The detection rectifier circuits 11 are connected in order,
The configuration is such that the reproduction signal of the MR element 1 is output to an output terminal 12. As shown in FIG. 2 (bl), the high frequency bias current circuit 7 supplies the bias conductor 3 with Ib,
, A high frequency current that changes between two values of Ib2 flows through the lead wire 6.
c, it flows through the connecting terminals 4b, 4a and the grounded lead 6a. The frequency of this high frequency current may be at least twice the upper limit of the signal frequency. In this embodiment, this upper limit is set to 50 kHz, and a high frequency current of 50 kHz is used.

Figure 3 shows the resistance change Δ against the input magnetic field H of the MR element 10.
This is an operating curve showing ψ, and the operating point changes alternately between )(rbt l HIb2) due to the high frequency bias current. 12 is the input signal magnetic field.

It is in a state where it is superimposed on the magnetic field generated by the high frequency bias current. Reference numeral 13 indicates the output signal of the MR element 1, which is a high frequency signal whose envelope is the input signal.

Also, the part marked A is in a normal playback state, and the part marked B is a state in which, for example, the element temperature rises due to frictional heat, the overall resistance shifts to the high resistance side, and the playback signal has level fluctuations. be.

Here, the sample hold circuit 9 shown in FIG. By performing the calculation of αn A in FIG. 3 by the differential circuit 10, the signal is converted into a signal having an envelope as shown in FIG. 4. By processing this signal by the detection rectifier circuit 11.

An electrical signal corresponding to the input magnetic field signal of the MR element 1 is obtained at the output terminal 12. It goes without saying that setting the bias operating point HIbl at a steep slope of the Δψ-H curve increases the reproduction sensitivity.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to prevent the generation of thermal noise that is difficult to avoid with a single magnetoresistive element.
A reproduction signal free of thermal noise can be obtained, and a magnetoresistive reproduction head with excellent functions can be provided without the drawbacks of the prior art described above.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of the magnetoresistive reproducing head according to the present invention, FIG. 2 is a waveform diagram showing the current applied to the magnetoresistive element of FIG. 1, and FIG. fbl
is a waveform diagram of the high frequency bias current in FIG. 1, FIG. 3 is an explanatory diagram of the operation of the embodiment shown in FIG. 1, FIG. 4 is a waveform diagram showing its output signal, and FIG. 5 is the operating principle of the present invention. It is a diagram. l...Magnetoresistive element. 3...Bias conductor 1゜7...High frequency bias current circuit. 9...Sample hold circuit. 10...Differential circuit. <Reactor agent Masaru Ogawa, deceiver 1 m

Claims (1)

[Claims] In a magnetoresistive read head configured to determine the operating point of the magnetoresistive element by a magnetic field generated by passing a current through a bias conductor provided close to the magnetoresistive element, a high frequency wave is applied to the bias conductor. In addition to connecting the current circuit, the output signal of the magnetoresistive element is divided into two, one is supplied to the differential amplifier, and the other is supplied to the differential amplifier via the sample and hold circuit. A magnetoresistive reproducing head characterized in that a sampling period is made to match the period of a bias high-frequency current.