JPS58208902A - Reproducing amplifying circuit for multi-track mr head - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reproduction amplification circuit for a multi-track MR head, which is made up of an aggregate of a plurality of magnetic heads using the magnetoresistive effect.

Conventionally, electromagnetic induction type magnetic heads have been mainly used as magnetic heads used in magnetic recording/reproducing devices such as tape recorders. In recent years, with the increasing demand for high-density recording and advances in thin film technology, magnetoresistive elements (Af
Multi-track 1dR recording heads, which are composed of a plurality of magnetic heads using an R element (referred to as an R element), have come into use.

This magnetic head utilizes the resistance change of a ferromagnetic thin film such as permalloy due to an external magnetic field, and an example of this magnetic head is shown in FIG.

In FIG. 1, 1 and 2 are metal electrodes, 6 is a ferromagnetic thin film, 4 is a magnetic recording medium, MT is the magnetization vector of the magnetic recording medium 4, M is the magnetization vector of the forced thin film 1lyX5, and I is the ferromagnetic thin film. 5, and metal Vt other pole 1.
When there is no external a-field, the angle θ between the current vector I and the magnetization vector M of the ferromagnetic thin film 5 is 45°. Note that 10 indicates the entire MR hect.

When the magnetic recording medium 4 whose external signal magnetization vector AfT changes by iAh comes into contact with this MR hect.

Due to the magnetic field of the magnetization vector Afr, the angle 0 between the magnetization vector M of the ferromagnetic dilution 5 and the current vector I becomes the magnetization vector M.
It changes according to the change ΔMr in T, and is obtained as the resistance change ΔR of the ferromagnetic thin film 5 according to the change ΔMr in the magnetization vector AIT of the recording medium 4, as shown in the m2 diagram. Therefore, by detecting this resistance change iR as a potential difference between the metal electrodes 1 and 2, it is possible to read out the signal recorded on the recording medium 4 as a signal.

Therefore, in order to read and reproduce a distributed signal using this MR head, a drive current circuit that supplies 5111t to the MR head and an amplifier circuit that detects the resistance change of the MR element are required. For this reason, conventionally, a reproducing amplification circuit for a multi-track AfR head has been used in which these circuits are configured separately, for example, as shown in FIG. 3, for a plurality of tracks.

In FIG. 5, 10-1 to 10-n are respectively 1st to 10-n.
Lutrak MR head, 11 is a transistor, 12 is a differential amplifier circuit, 15-16 is a capacitor, 17 variable resistors, 18-22 are resistors, 23 DC power supplies, 24-1-2
4-n are output signals of the first to nth tracks, respectively.

In this circuit, the transistor 11ViAf/? For driving head N cap 1, l:lt variable resistance 17 resistance 18
19 and the power supply voltage of the DC power supply 25 determine the drive current. If the MR head is driven with a constant current, the resistance of the MR head changes in proportion to the external magnetic field applied to the MR head, so the collector voltage of the transistor 11 changes, and this voltage change is absorbed by the differential amplifier circuit. 12, capacitor 14-1
6. The signal from the recording medium 4 can be read by amplifying and extracting it using an amplifier circuit composed of resistors 20 to 22.

However, in this conventional example, since the current drive circuit and the amplifier circuit are provided independently, there are drawbacks such as a complicated configuration and a significant increase in cost. In addition, in the conventional example described above, the noise sources are the resistance noise of the MR head and the noise caused by the transistors in the differential amplifier circuit 12, as well as the noise caused by the resistance 19 of the resistor 19.
．． Since many noises such as thermal noise from the transistor 21 and noise from the transistor 11 are included in the noise, it is difficult to reduce the noise and it is difficult to maintain sufficient circulation.

Further, when the above-mentioned reproduction amplification circuit is used as a reproduction amplification circuit for a multi-track MR head.

There is a drawback that the driving current of the 1MR head must be finely adjusted for each track using a variable resistor 17 due to variations in the voltage between the base and emitter of the transistor.

The purpose of the present invention is to eliminate the above-mentioned drawbacks of the prior art, to simplify the circuit configuration, to easily reduce noise, and to simplify the adjustment of drive currents for multiple tracks. The present invention provides a reproduction amplification circuit for a track MR head.

The present invention takes advantage of the fact that the elements constituting the t'dR head are the same as the resistance under equal constraints, and that there is little variation in resistance between elements fabricated at the same time due to the use of thin film formation technology in the manufacturing process [7, A regenerative amplifier was constructed so that a constant DC reverse pressure could be obtained at its input, and the amplifier was used for multiple tracks to simplify the adjustment of the drive current for multiple tracks and to reduce noise. Be mindful of things.

Hereinafter, the present invention will be explained in detail with reference to embodiments shown in the drawings.

A concrete example circuit diagram according to the present invention is shown in FIG. In FIG. 4, 6-1 to 6-n are IfR head regeneration increase 1m1 circuits for the 1st to rL tracks, and 10-1 to 6-n, respectively.
10-n are the AIR hects of the 1st to nth tracks, respectively;
12 is a differential amplifier 1 @ circuit, 1 (S, 25 is a capacitor, 2
5 is a DC power supply, 24-1 to 24-r are 1st to r, respectively.
Output number terminals of AfR head of L track, 26-27
is a resistor, 28 is a variable resistor, and 29 is a drive voltage circuit.

Referring to FIG. 4, the operation of the MR head reproduction amplification circuit for each track will be explained. If the open loop gain of the differential amplifier circuit 12 is sufficiently higher than the closed loop gain, the resistor 26 and the MR heads 10-1 to 10-
Each MR head 10-1 is connected via the resistor 26 so that the voltage at the connection point of the drive voltage circuit 29 is equal to the voltage at the connection point between the resistor 27 and the variable resistor 2B.
~10-n is supplied with current.

The output of the MR head is such that when the resistance of the pMR head changes due to the magnetic field in the tape, the feedback current changes so that the voltage at the connection point between the MR head and the resistor 26 is always equal to the output voltage of the drive voltage circuit 29. , MR is connected to both ends of the resistor 26.
An output voltage proportional to the change in resistance of the head can be obtained. In addition, in the amplifier circuits 6-1 to 5-n of each track, only the resistance noise of the MR heads 10-1 to 10-1 and the transistor noise of the differential amplifier circuit 12 are used as noise sources. A low-noise regenerative amplifier circuit can be realized simply by using a low-noise transistor as the first-stage transistor of the amplifier circuit 12.

Furthermore, since the manufacturing process of the elements constituting the MR head uses a thin film formation technique, there is little variation in resistance among the casings 10-1 to 10-n of the MR heads manufactured at the same time. Therefore, in FIG. Simply connect the output of the drive voltage circuit 29 composed of a resistor 27 and a variable resistor 28 to the non-inverting input side of the differential amplifier circuit 12 of each track, and vary the output voltage of the drive voltage circuit 29 with the variable resistor 28. This makes it possible to adjust the MR head drive current for each track at the same time, significantly improving operability.

As explained above, according to the present invention, the amplification of the MR head signal and the supply of drive current to the MR' By being able to simultaneously adjust the 6" drive ring of the AIR head of the track, it is possible to realize a regeneration tank circuit for a multi-track MR head with a simple structure and low noise without the drawbacks of the prior art.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing an example of an MR head, Fig. 2 is a characteristic diagram for explaining its operation, Fig. 5 shows a conventional example of a reproducing amplification circuit for a multi-track MR head, 1-Circuit diagram, Fig. 4 1 is a circuit diagram showing an embodiment of the present invention; FIG. 10-1~In-n: Magnetoresistive magnetic head (MR
head), 11: Transistor for supplying drive current of IdR head, 12: Differential amplifier circuit, 2B: i5J variable resistor for adjusting drive current of MR head, 2
9: Drive voltage circuit. t 1 Figure 0 Year 3 Figure 't' 4 Mouth

Claims (1)

[Claims] (Li) A magnetic head amplifier circuit using a magnetoresistive element has a non-inverting input and an inverting input, and by keeping one of these inputs at a nearly constant potential, the other input can be kept at a nearly constant potential. means for connecting the magnetic head formed by the magnetoresistive element between the amplifying circuit and the other input and a common potential, the connecting means connects the magnetic head, and the drive current for the magnetic head is A reproduction amplification circuit configured such that the supply of the signal and the amplification of the reproduced signal can be commonly performed by the amplifier circuit are provided for a plurality of tracks of the magnetic head. Connect the magnetic head of the track,
1. A reproducing amplifier circuit for a multi-track MR head, characterized in that the other input is common to each track and is configured to connect a drive voltage circuit, and is comprised of an assembly of magnetic heads made up of a plurality of magnetoresistive elements.