JPS6120051B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a magnetic recording/reproducing device using a magnetoresistive element (hereinafter referred to as an MR element).

MR elements are characterized by a large output voltage, but the output is not proportional to the input signal magnetic field. However, when an MR element is used in a magnetic recording/reproducing device, it has the disadvantage that the reproduced signal is distorted with respect to the original signal.

A magnetic recording/reproducing device which eliminates this drawback has been considered, and this device is shown in FIG. In this figure, 1 is an MR element, 2 is a coil that constitutes a magnetic head with MR element 1, 3 is a DC power supply, 4 is a current limiting resistor, 5 is an amplifier, 6 is a differential amplifier, and 7 is a reference voltage generator. , 8 is a coil current source, 9 is a coil current control circuit, 10 is a current/voltage conversion circuit, and 11 is an output terminal.

Next, the operation of the magnetic recording/reproducing apparatus configured as described above will be explained. Due to the so-called "magnetoresistive effect," when the MR element 1 receives a signal magnetic field from a recording medium (not shown), its electrical resistance value changes in a special relationship with respect to the magnetic field. The DC power supply 3 converts the resistance value into a voltage signal and detects it by passing a DC current through the MR element 1 via the current limiting resistor 4. This voltage signal is amplified by the amplifier 5 and the difference is It becomes one input of the dynamic amplifier 6. On the other hand, the reference voltage generator 7 determines in advance an input magnetic field in a region where the change in resistance value is the largest with respect to fluctuations in the input magnetic field of the MR element 1, and stores a voltage equal to the output voltage after amplification in this magnetic field, This voltage is used as a reference voltage and is generated for the other input of the differential amplifier 6. Then, the differential amplifier 6 amplifies the difference between the reference voltage and the actual output voltage and inputs it to the coil current control circuit 9. On the other hand, a coil current flows through the coil 2 from a coil current source 8 via a current/voltage conversion circuit 10 and a coil current control circuit 9, and the MR as well as the signal magnetic field from the recording medium
A magnetic field is applied to element 1. In this case, there is a good proportional relationship between the coil magnetic field and the coil current, and the coil current is controlled based on the output of the differential amplifier 6 so that the above reference voltage matches the actual output voltage. Controlled by circuit 9. That is, in this type of magnetic recording/reproducing device, a coil magnetic field is applied so that the signal magnetic field from the recording medium is canceled and the output voltage of the MR element 1 is always constant, and the change in the coil current that occurs at this time is the signal magnetic field. This coil current is converted into a voltage signal by the current/voltage conversion circuit 10 and outputted to the output terminal 11 by utilizing the fact that the current corresponds to the change in the voltage. In this case, the input magnetic field of the MR element 1 is adjusted so that its output voltage becomes a substantially constant voltage. Therefore, distortion of the reproduced output due to nonlinearity between the input magnetic field and the output voltage (resistance value) of the MR element 1 is completely eliminated.

However, the magnetic recording/reproducing apparatus as described above has a drawback that the reproduction output decreases or disappears due to temperature changes of the MR element 1. That is, the rate of change in the resistance value of the MR element 1 due to the input magnetic field is at most about 2% of the resistance value of the element itself.
On the other hand, the rate of change in resistance value due to temperature change of the MR element 1 is about 0.6%/°C. therefore,
If the temperature of MR element 1 changes by several degrees from the temperature at the time the reference voltage was set, the resistance value of MR element 1 will not be able to output an output voltage equal to the reference voltage under the input magnetic field. It becomes unusable. Furthermore, by the time this state is reached, the output voltage has passed through a region where the change in the output voltage is small relative to the change in the input magnetic field, so the reproduction output becomes small at this point.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and involves superimposing a fixed value of DC current and an AC current controlled based on the AC component of the MR element output to flow through the coil. By doing this, the output voltage can be set in the region where the resistance value changes greatly due to magnetic field fluctuations of the MR element, regardless of the temperature change of the MR element, and at the same time, distortion can be maintained for AC signals such as video and audio as before. It is an object of the present invention to provide a magnetic recording and reproducing device that can generate a reproduction output that is unique.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows a magnetic recording/reproducing device according to one embodiment, and in this figure, 1 is an MR element, and 2 is an MR element.
A coil 3 that constitutes a magnetic head with the MR element 1
is a DC power supply, 4 is a current limiting resistor, 5 is an amplifier, 8
9 is a coil current source, 9 is a coil current control circuit, and 10 is a coil current source.
1 is a current/voltage conversion circuit, 11 is an output terminal, 21 is a capacitor connected to the input of the amplifier 5, and 22 is a current regulating resistor. In this case, a constant DC current is passed through the coil 2 from the coil current source 8 through the current regulating resistor 22, and the current/voltage conversion circuit 10 and the coil are connected in parallel with the current regulating resistor 22. A current is passed through the coil 2 via the current control circuit 9. Further, the current passing through the coil current control circuit 9 is amplified by the amplifier 5.
The coil current control circuit 9 is controlled by the AC component signal of the output of the MR element 1 to cancel this output. Further, the current/voltage conversion circuit 10 converts the controlled current into a voltage and outputs it to the output terminal 11.
The DC power supply 3 is the same as the conventional one.

That is, although the resistance value of the MR element 1 changes with temperature changes, the change in magnetic characteristics is relatively small in the general operating temperature range. Therefore, in the above device, the current regulating resistor 22 is adjusted to set the coil magnetic field when there is no signal in a region where the resistance value changes greatly in response to changes in the input magnetic field of the MR element 1. Since the signal magnetic field is superimposed at the center, even if the temperature changes, the resistance value will not deviate from the region where the change is large. This point is a major difference between conventional devices and the above devices. Conventionally, MR
Although the resistance value of element 1 was used as the standard, in the above device,
A reference was established for the input magnetic field to the MR element 1.
On the other hand, regarding the distortion of the reproduced output, the coil current is controlled to keep the output of MR element 1 constant as in the conventional case, and the output is reproduced from the coil current. Since we can take advantage of the very good proportionality of

FIG. 3 is a specific circuit diagram of the above device. In this figure, 1 is an MR element, 2 is a coil, 11 is an output terminal, 31 to 36 are resistors, 41 to 44 are capacitors, 51 is a transistor, and 52 is a power supply, 53
is earth. The resistor 31 and the capacitor 41 form a stabilizing circuit for flowing direct current to the MR element 1, and the resistor 332 is a resistor for limiting the current to the MR element 1. This element direct current is supplied from the power supply 52 to the resistors 31, 32 and
It flows through the MR element 1 to the ground 53. Only the alternating current component of the voltage change based on the signal magnetic field from the recording medium is applied to the base electrode of the transistor 51 via the capacitor 42 . On the other hand, the coil current flows from the power source 52 through the resistor 33, the coil 2, the collector electrode of the transistor 51, and the emitter electrode to the ground 53. The resistors 34, 35, and 36 and the capacitor 44 create a voltage that very slowly follows the opposite polarity as the coil current increases and decreases, and this voltage regulates the amount of DC current component flowing through the coil 2. The amount of base current of transistor 51 is determined. An AC component based on the output of the MR element 1 applied via the base electrode of the DC component and the capacitor 42 is simultaneously applied to the base electrode of the transistor 51, and these signals are applied to the base electrode of the transistor 51.
The current is amplified by 1 and becomes the current of coil 2.
Also, in this circuit, the output is capacitor 4
3 to the output terminal 11.

In addition, to explain the phase between such a specific circuit and FIG. 2, the DC power supply 3 in FIG. 2 corresponds to a stabilizing circuit including a resistor 31 and a capacitor 41.
In this case, the resistor 31 may be replaced with a coil.
Further, the current limiting resistor 4 corresponds to the resistor 32, and the transistor 51 functions as both the amplifier 5 and the coil current control circuit 9. Coil current source 8 is connected to power source 52
The current/voltage conversion circuit 10 performs this by detecting the voltage drop using the resistor 33. Further, the capacitor 21 is a capacitor 42, and the regulating resistor 22 has a function corresponding to that of the resistors 34, 35, and 36, so that an appropriate DC coil current automatically flows together with the capacitor 44. Note that in FIG. 3, when the output of the MR element 1 is small, it is effective to insert an amplifier circuit between the MR element 1 and the capacitor 42.

As described above, according to the magnetic recording and reproducing apparatus according to the present invention, since the conventional reference voltage setting method is changed to the reference coil magnetic field setting method, the operating temperature range is widened, and the distortion of the reproduced output is reduced. It has the effect of obtaining something.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional magnetic recording/reproducing device, FIG. 2 is a block diagram showing an embodiment of the magnetic recording/reproducing device according to the present invention, and FIG. 3 is a specific circuit diagram of the device according to the present invention. . 1...MR element, 2...coil, 3...DC power supply, 4
...Current limiting resistor, 5...Amplifier, 8...Coil current source, 9...Coil current control circuit, 10...Current voltage conversion circuit, 11...Output terminal, 21...Capacitor, 2
2... Regulatory resistance, 31-36... Resistance, 41-44...
Capacitor, 51...transistor, 52...electrode.
Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A magnetic head consisting of a magnetoresistive element and a coil that applies a magnetic field to the element, a circuit that detects an alternating current component of the output of the magnetoresistive element,
A circuit that has a power source that allows current to flow through the coil and can superimpose a constant DC current and a current controlled based on the output of the upstream magnetoresistive element with respect to the coil current, and a circuit that can convert the controlled current amount into a voltage. A magnetic recording/reproducing device comprising a circuit for converting into a value. 2 Has a DC power supply, a capacitor and an amplifier,
Direct current is passed from a DC power supply to the magnetoresistive element, and the output voltage generated at both ends of this element is amplified by the AC component through a capacitor.
The resistor and the coil current control circuit are inserted between the current path from the power supply to the coil to cause the coil current to flow, and based on the output signal of the amplified alternating current component, the above-mentioned 2. The magnetic recording and reproducing apparatus according to claim 1, wherein the coil current is controlled by a coil current control circuit. 3 It has a transistor as an amplifier, uses a capacitor and a group of resistors to smooth the output voltage for its base current, and also uses a control current corresponding to the DC component of the coil current that has been adjusted and the output signal of the magnetoresistive element. Claims 1 or 2, characterized in that the transistor has both the functions of output amplification and control of the coil current by applying the voltage in a superimposed manner and connecting the coil to the collector electrode of the transistor. The magnetic recording and reproducing device described in .