JPH09147303A - Magnetic recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide means for obtaining a best S/N in any of cases where a noise reduction effect is switched On and OFF in a magnetic recording/ reproducing device using an MR element as a magnetic reproducing head. SOLUTION: By a first switch element 4 switched associatively with a second switch element for switching ON/OFF the noise reduction effect of a noise reduction part 13, a first current source is supplied from a first power source 7 through a first resistor 5 to a MR element 2 when the noise reduction effect is switched ON, a second current source is supplied from the first power source 7 through a second resistor 6 to the MR element 2 when the noise reduction effect is switched OFF. Thus, by switching a sense current supplied to the MR element 2 associatively with the switching ON/OFF of the noise reduction effect so as to give an optimal sense current, a best S/N is obtained overall.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus using an MR element as a magnetic reproducing head of a tape recorder or the like.

[0002]

2. Description of the Related Art In recent years, a magnetic reproducing apparatus for music using an MR element as a magnetic reproducing head of a tape recorder has been proposed and put into practical use. An example of a conventional magnetic recording / reproducing apparatus will be described below with reference to the drawings. FIG.
7 is a block diagram showing an example of a conventional magnetic recording / reproducing apparatus. In FIG. 7, a constant current is supplied from a current source 102 to an MR element 101 as a magnetic reproducing head installed in a magnetic tape running system. The reproduction output of the MR element 101 is input to the noise reduction unit 105, and the output of the noise reduction unit 105 is connected to the output end 107. The switch element 106 is the noise reduction unit 105.
It is connected to turn on and off the noise reduction effect of.

The operation of the conventional magnetic recording / reproducing apparatus having the above structure will be described below. MR element 101 in which a magnetic flux change of a signal recorded on a magnetic tape (not shown) traveling in a magnetic tape traveling system is in contact with the magnetic tape
Is converted into a change in resistance value. By supplying a constant current from the current source 102 to the MR element 101, the MR element 1
The change in the resistance value of 01 depends on Ohm's law.
It is converted into the voltage change of the both ends. The current supplied by the current source 102 is a so-called sense current. When the change in the resistance value of the MR element 101 when the change in the magnetic flux is ΔΦ is Δr, the voltage change Δe across the MR element 101 due to the current value I of the current source 102 is Δe = Δr · I (1) . This voltage change is input to the noise reduction unit 105 as a signal, and is decoded by the noise reduction unit 105 to reduce noise, and is output to the output terminal 107. At this time, the larger the current value I of the current source 102 is, the larger the output of the MR element 101 can be obtained as can be seen from the equation (1). Therefore, noise generated in the noise reduction unit 105 (mainly due to thermal noise caused by signal source impedance is high). The signal output for the area component noise) can be increased and the S / N ratio can be increased.
1 generates heat, and so-called sliding noise caused by sliding of the magnetic tape on the surface thereof increases noise in the low-frequency component, so that the relationship between the sense current and the signal-to-noise ratio is as shown in FIG.

For this reason, the thermal noise and the sliding noise are combined to set the current value at which the signal-to-noise ratio becomes the best. On the other hand, depending on whether or not the signal recorded on the magnetic tape is encoded by the noise reduction circuit on the recording side at the time of recording, the switching element 106 can select ON / OFF of the noise reduction circuit of the noise reduction unit 105. it can.

[0005]

However, in the above-described conventional magnetic recording / reproducing apparatus, when the noise reduction unit 105 uses the noise reduction circuit of the high frequency noise reduction type conventionally proposed and used, Since the distribution of noise components with respect to the frequency when the noise reduction effect of the noise reduction unit 105 is turned on by the switch element 106 is lower than the distribution of the noise component when the noise reduction effect is turned off by the switch element 106, the high frequency component is lowered. Noise reduction effect The optimum value of the current value I of the current source 102 when turned on is smaller than the optimum value when the noise reduction effect is turned off by the switch element 106, and the optimum value is different as shown in FIG. was there.

The present invention is intended to improve the above-mentioned problems of the prior art, and the best signal-to-noise ratio is obtained when the noise reduction circuit of the noise reduction unit 105 is turned on and off by the switch element 106. It is intended to provide a magnetic recording / reproducing apparatus that supplies the respective sense current values as described above and obtains the best signal-to-noise ratio when the noise reduction circuit is turned on or off. .

[0007]

In order to solve the above problems, a magnetic recording / reproducing apparatus of the present invention comprises an MR element used as a magnetic reproducing head, a first current source, a second current source, and A first switch element for selecting a first current source and the second current source and supplying the selected MR element to the MR element;
A noise reduction section for inputting a signal of an R element and a second switch element for turning on / off the noise reduction effect of the noise reduction section, wherein the first switch element and the second switch element are It is equipped with a configuration that operates in conjunction with each other.

According to the present invention, with the above-described structure, the current source supplied to the MR element by the first switch element that operates in conjunction with the second switch element that turns on and off the noise reduction effect is the first current source and the second current source. Switch to current source.
The set current value of the first current source is set to a current value that gives the best signal-to-noise ratio when the noise reduction effect is on, and the set current value of the second current source when the noise reduction effect is off. The best signal-to-noise ratio can be obtained regardless of whether the noise reduction effect of the noise reduction section is on or off by setting the current values that give the best signal-to-noise ratio.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention comprises an MR element used as a magnetic reproducing head, and
First current source, a second current source, the first current source and the second current source, and supplies them to the MR element.
Switch element, a noise reduction section for inputting a signal of the MR element, and a second switch element for turning on / off the noise reduction effect of the noise reduction section, and the first switch element and the first switch element. The current is supplied to the MR element by the first switch element that is interlocked with the second switch element that turns on and off the effect of the noise reduction unit. Switching the source between a first current source and a second current source. The set current value of the first current source is set to a current value that gives the best signal-to-noise ratio when the noise reduction effect is on, and the set current value of the second current source when the noise reduction effect is off. By setting the respective current values that give the best signal-to-noise ratio, the noise-reduction section acts so as to have the best signal-to-noise ratio regardless of whether the effect is on or off.

According to a second aspect of the present invention, an MR element used as a magnetic reproducing head, a bias conductor for applying a bias magnetic field to the MR element, a first current source, and a second current source are provided. , A first switch element for selecting the first current source and the second current source to supply the MR element, and a DC voltage for generating a bias magnetic field from the bias conductor to the MR element. A bias power supply for applying the voltage, magnetic negative feedback means for magnetically negatively feeding back the MR element by amplifying the terminal voltage of the MR element and applying a feedback voltage to the bias conductor,
A noise reduction section for inputting a signal of an R element and a second switch element for turning on / off the noise reduction effect of the noise reduction section, wherein the first switch element and the second switch element are It is configured to operate in conjunction with each other, and to superimpose a feedback voltage of the magnetic negative feedback means on a DC voltage from the bias power source and apply the superimposed voltage to the bias conductor. The negative feedback means acts to compensate the nonlinearity of the magnetic hysteresis curve and reduce the distortion of the reproduction output.

According to a third aspect of the present invention, in the second aspect of the invention, when the supply current to the MR element changes, the magnetic negative feedback means does not generate a pulse magnetic field that saturates in the direction of the bias magnetic field. In addition to the function of claim 2, the magnetic field provided by the bias conductor is saturated in the direction of the bias magnetic field due to the change in the current supplied to the MR element, and the use area of the MR element has a predetermined hysteresis characteristic curve. It prevents the output from deviating from the region (1) and obtains a reproduction output with good linearity and little distortion.

Embodiments of a magnetic recording / reproducing apparatus of the present invention will be described below in detail with reference to the drawings. FIG.
1 is a block diagram of a main part of a magnetic reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a characteristic diagram showing a relationship between a magnetic field and a magnetic resistance of an MR element, and FIG. 4 is a diagram of hysteresis characteristics of the MR head 1.

In FIG. 1, the MR element 2 and the bias conductor 3 are integrated to form an MR reproducing head 1.
A sense current from the first power supply 7 is applied to the MR element 2 through the switch element 4 through the first resistor 5 or the second resistor 6 having a smaller resistance value than that of the first resistor 5.
The first power source 7 and the first resistor 5 form a first current source to be supplied to the MR element 2, and the first power source 7 and the second resistor 6 are a second current source to be supplied to the MR element 2. Is formed.

The connection point between the switch element 4 and the MR element 2 is connected to the (+) input terminal of the first operational amplifier (hereinafter OP amplifier) 8. First O
Between the (-) input terminal of the P amplifier 8 and the ground, a third
A resistor 9 and a first capacitor 10 are connected in series, and a fourth resistor 11 is connected between the output terminal and the (−) input terminal of the first OP amplifier 8.

From the output terminal of the first OP amplifier 8 to the second
The capacitor 12 is connected to the input of the noise reduction unit 13. The noise reduction section 13 is connected to a second switch element 14 for turning on / off the noise reduction effect, and turns on the noise reduction effect on the terminal 14a side and turns off the terminal 14b side. The second switch element 14 operates in conjunction with the first switch element 4, and operates the second switch element 14 to operate the terminal 1
When connected to the 4a side and the noise reduction operation of the noise reduction unit 13 is turned on, the first switch element 4 is connected to the 4a side to select the first current source, while the second switch element is connected. When the noise reduction operation of the noise reduction unit 13 is turned off by operating 14 and connecting to the side of 14b, the first switch element 4 is set to 4
The second current source is connected so as to be selected by connecting to the b side. The output of the noise reduction unit 13 is connected to the output end 15.

On the other hand, the second OP amplifier 20 is branched from the output terminal of the first OP amplifier 8 through a parallel circuit of a third capacitor 16 and a zener diode 17 having the illustrated polarity and a fifth resistor 18. Connected to the (-) input terminal of
The sixth resistor 19 is connected between the (−) input terminal and the output terminal of the OP amplifier 20. The (+) input terminal of the second OP amplifier 20 is connected to the second power supply 21 having a positive polarity DC voltage, and the output terminal of the second OP amplifier 20 is connected to the bias conductor 3.

The above-mentioned configuration is described below. A signal recorded on a magnetic tape (not shown) running in the magnetic tape running system is converted into a change in resistance value by the MR element 2 of the MR reproducing head 1 in contact with the magnetic tape. First, when the switch element 14 is switched to the contact 14a side corresponding to the ON side of the noise reduction effect, the interlocking first switch element 4 is switched to the contact 4a side, whereby the first power supply 7 and the first resistor 5 are connected.
When the noise reduction effect is turned on and the optimum current I1 is supplied to the MR element 2, the resistance change of the MR element 2 is converted into a voltage change across the MR element 2 according to Ohm's law.

When the change in the resistance value of the MR element 2 when the change in the magnetic flux is ΔΦ is Δr, the voltage change Δe1 across the MR element 1 due to the current value I1 of the first current source is Δe1 = Δr · I1 (2) On the other hand, when the second switching element 14 is operated to turn off the noise reduction effect, the first power source 7 and the second resistor 6 select the second current source by the interlocking first switching element 4. The optimum sense current I2 is supplied to the MR element 2 when the noise reduction effect is turned off. At this time, the voltage change Δe2 across the MR element 1 due to the current value I2 of the second current source is Δe2 = Δr · I2 (3) Becomes This voltage change is used as a signal for the first OP amplifier 8
Is input to the noise reduction unit 13 via the second capacitor 12 and is amplified by the noise reduction unit 13
Noise is reduced by being decoded by the output terminal 1
5 is output.

On the other hand, the DC voltage of the second power source 21 is applied to the bias conductor 3 from the (+) terminal via the second OP amplifier 20, and gives a bias magnetic field to the MR element 2.
From the characteristic diagram showing the relationship between the magnetic field and the magnetic resistance of the MR element in FIG. 2, the relationship between the change in the magnetic field H and the change in the resistance value Δr of the MR element 2 is non-linear near the zero point of the magnetic field H, and A magnetic field is applied to shift the operating point to the center of the straight line portion of the characteristic to reduce the distortion in the use area. Even with this, a small amount of non-linearity remains, so the first OP amplifier 8
From the output terminal of the third capacitor 16 and the fifth resistor 18
Then, the (−) terminal is applied to the bias conductor 3 by the second OP amplifier 20 and magnetically negatively fed back from the bias conductor 3 to the MR element 2 to improve the distortion. This loop is used as a magnetic negative feedback means.

Next, the circuit operation when the switch element 4 is switched will be described with reference to FIG. Switch element 4 to 4a
When switched from 4b to 4b, the MR element 2 is supplied with the sense current I2 from the first power supply 7 through the second resistor 6. As described above, since the second resistor 6 has a smaller resistance than the first resistor 5, the sense current increases, and the voltage across the MR element 2 changes as shown in FIG. Then, the output potential of the first OP amplifier 8 once rises to the power supply voltage in the (+) direction and is fed back through the fourth resistor 11, but in order to increase the amplification factor of the OP amplifier 8, the resistance is increased. 11
Has a large resistance value, the third resistor 9 has been set to a small value, and the first capacitor 10 has a large capacitance, so that the capacitor 10 is charged and the OP amplifier 8 stabilizes as an amplifier. It takes about 1 second to recover. This state is shown in FIG. The solid line in FIG. 3C is the potential at the other end (− side) of the third capacitor 16 when the Zener diode 17 is not provided, and as the potential in FIG. 3B increases to the (+) side power supply voltage. This potential also rises. After that, the potential drops as the capacitor 16 is charged, but when the OP amplifier 8 returns as an amplifier, a potential on the (-) side of the figure is generated due to the potential charged in the capacitor 16, but after that, it is discharged. The potential drops. This potential is amplified by the second OP amplifier 20,
The solid line in FIG. 3D in which the potential of the solid line in (c) is inverted is OP.
It becomes the output waveform of the amplifier 20.

When the waveform of FIG. 3 (d) is applied to the bias conductor 3, the hysteresis characteristic of the MR head 1 including the MR element 2 and the bias conductor 3 of FIG. The pulse on the −) side moves to point (1) on the curve in FIG. 4, and as the (−) potential decreases, (2)
However, it moves to the point (3) by the next (+) pulse, and as the (+) potential decreases, it is biased at the point (5) by the output of the second OP amplifier 20 on the path (4). Since the magnetic field is set, the linear portion is narrow and applied to the non-linear portion, so that distortion occurs.

Therefore, by adding the Zener diode 17 of FIG. 1, the capacitor 16 is charged only up to the Zener voltage, so that the capacitor 18 side (−).
3C, the potential waveform is as shown by the broken line in FIG. 3C, and therefore the output voltage of the second OP amplifier 20 is as shown by the broken line in FIG. 3D, and the (+) side pulse is suppressed. Therefore, it is stabilized on the path (2) of the hysteresis characteristic of FIG. With the output of the second OP amplifier 20 that amplifies the voltage of the second power supply 21 as the bias power supply, the bias magnetic field is set substantially at the center of the straight line portion at the point (6), whereby reproduction with less distortion can be performed. This operation is the same as when the sense current is decreased or when the power is turned on or the like.
It can act to suppress the pulse to the (+) side of (d). Here, the role of this circuit configuration and the Zener diode 17 is to prevent generation of a pulse magnetic field that saturates in the direction of the applied bias magnetic field when the sense current changes. Therefore, the modification of the circuit configuration achieved for this purpose is included in the present invention.

Next, the setting of the sense current when the noise reduction effect is turned on and off by the first resistor 5 and the second resistor 6 will be described. FIG. 5 is a frequency characteristic diagram of the noise voltage with the sense current given to the MR element 2 as a parameter, and FIG. 6 is a frequency characteristic diagram of the noise voltage for ON / OFF of the noise reduction effect. As shown in FIG. 5, when the sense current is increased, the high frequency S / N ratio is improved but the low frequency S / N ratio is deteriorated. When the noise reduction is turned on as shown in FIG. 6, the high frequency S / N ratio is improved. When the noise reduction is off, the high frequency noise component is predominant in the total noise, so the sense current I2 is set to a large value to increase the output and the high frequency due to the signal source impedance generated in the noise reduction unit 13 is caused. Set to suppress component noise. By suppressing the high frequency noise in this way, the overall S / N ratio can be improved. When the noise reduction effect is on, the high-frequency noise component is reduced in all the noise, and the low-frequency noise component is conspicuous. Therefore, the sense current I1 is set small and the low-frequency noise component due to sliding noise is set to be suppressed. The overall S / N ratio can be improved.

As described above, according to the present embodiment, the first sense current is supplied when the noise reduction effect is turned on.
Switching element 4 and the second current source which supplies an optimum sense current when the noise reduction effect is turned off, and supplies the first switching element 4 to the MR element 2 of the MR reproducing head 1.
By interlocking with the second switching element 14 that selects the noise reduction effect, the difference between the frequency-to-noise components when the noise reduction effect of the noise reduction unit 13 is on and when it is off Since an optimum sense current value can be set for each of them, the best signal-to-noise ratio can be obtained for each.

Further, the magnetic negative feedback means of the present embodiment, and further, when the supply current to the MR element is changed, the magnetic negative feedback means is configured so as not to generate a pulse magnetic field which saturates in the direction of the bias magnetic field. It is possible to reduce the distortion caused by the magnetic non-linearity of the MR element and the erroneous setting of the bias magnetic field, and obtain a reproduction output with good linearity.

In the present embodiment, as is clear from the expressions (2) and (3), the output changes when the set current value changes, so that the noise reduction effect of the noise reduction section 13 is ON and OFF. In some cases, in order to make the output constant, a circuit for adjusting the gain in cooperation with the second switch element 14 may be added before or after the noise reduction unit 13.

Further, the illustrated circuit configuration and numerical values are examples,
It is not limited to this.

[0028]

As described above, the magnetic recording / reproducing apparatus of the present invention includes the MR element used as the magnetic reproducing head, the first current source, the second current source, and the first current source. A first switch element that selects and supplies the second current source to the MR element, a noise reduction section that inputs a signal of the MR element, and a noise reduction effect of the noise reduction section are turned on / off. A second switching element is provided, and the first switching element and the second switching element are configured to operate in conjunction with each other, so that the noise reduction effect is on and off, respectively. Since the optimum sense current value can be set for each difference in frequency-to-noise component, the best signal-to-noise ratio can be obtained.

Further, in addition to this structure, a magnetic negative feedback means is added, and further, when the supply current to the MR element is changed, a pulse magnetic field which saturates in the direction of the bias magnetic field is not generated in the magnetic negative feedback means. Depending on the configuration, M
It is possible to reduce the distortion caused by the magnetic non-linearity of the R element and the erroneous setting of the bias magnetic field, and obtain a reproduction output with good linearity.

[Brief description of the drawings]

FIG. 1 is a block diagram of a main part of a magnetic recording / reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing the relationship between the magnetic field and the magnetic resistance of the MR element.

FIG. 3 is a waveform chart of each part of the circuit accompanying switching of the first switch element 4 according to the embodiment of the present invention.

FIG. 4 is a hysteresis characteristic diagram of the MR head 1.

FIG. 5 is a frequency characteristic diagram of a noise voltage with a sense current given to the MR element 2 as a parameter.

FIG. 6 is a frequency characteristic diagram of noise voltage when the noise reduction effect is on / off.

FIG. 7 is a block diagram of a conventional magnetic recording / reproducing apparatus.

FIG. 8 is a characteristic diagram showing the relationship between the sense current and the signal-to-noise ratio of the MR element of the magnetic recording / reproducing apparatus.

[Explanation of symbols]

 1 MR reproducing head 2 MR element 1 3 Bias conductor 4 1st switching element 5 1st resistance 6 2nd resistance 7 1st power supply 8 1st OP amplifier 9 3rd resistance 10 1st capacitor 11 1st 4 resistance 12 2nd capacitor 13 noise reduction part 14 2nd switch element 15 output terminal 16 3rd capacitor 17 Zener diode 18 5th resistance 19 6th resistance 20 2nd OP amplifier 21 2nd power supply

Claims (3)

[Claims] 1. An MR element used as a magnetic reproducing head, a first current source, a second current source, the first current source and the second current source, and the MR element. A first switch element for supplying a signal from the MR element, and a second switch element for turning on / off the noise reduction effect of the noise reduction section, A magnetic recording / reproducing apparatus in which a switch element and the second switch element operate in conjunction with each other. 2. An MR element used as a magnetic reproducing head, a bias conductor for applying a bias magnetic field to the MR element, a first current source, a second current source, the first current source and the first current source. A first switching element for selecting the second current source and supplying it to the MR element; a bias power supply for applying a DC voltage to generate a bias magnetic field from the bias conductor to the MR element; A magnetic negative feedback means for amplifying a terminal voltage of the element and applying a feedback voltage to the bias conductor to magnetically give negative feedback to the MR element; a noise reduction section for inputting a signal of the MR element; A second switch element for turning on / off the noise reduction effect of the noise reduction section, wherein the first switch element and the second switch element are interlocked with each other. And a feedback voltage of the magnetic negative feedback means is superimposed on a DC voltage from the bias power source and applied to the bias conductor. 3. The magnetic recording according to claim 2, wherein the magnetic negative feedback means is configured not to generate a pulse magnetic field that saturates in the direction of the bias magnetic field when the current supplied to the MR element changes. Playback device.