JPH06150208A - Recording / reproducing device for magnetoresistive head - Google Patents

Abstract

(57) [Abstract] [Purpose] A low-pass filtering (LPF) capacitor for DC feedback and a differential amplifier (gm) for feedback to a first-stage transistor in a reproducing amplifier of a recording / reproducing device for an MR (magnetoresistive effect) head. In the one having an amplifier), the switching time is shortened by shifting the timing of switching the gm amplifier and the first-stage transistor at the time of recording / reproducing switching. [Structure] The output of the first-stage transistor 5 of the reproduction amplifier 4 for the MR head 1 is compared with a reference voltage V _ref1 by a gm amplifier 8, an LPF is constituted by gm of the gm amplifier 8 and a capacitor 9, and a DC output of the gm amplifier 8 is formed. In the case where the minute is fed back to the base of the first-stage transistor 5, the delay of the switching time due to the charging of the capacitor 9 caused by the difference in the rising time of the first-stage transistor 5 and the gm amplifier 8 is a control signal from the control circuit 24. The first-stage transistor 5 and the gm amplifier 8 are controlled by being shifted according to.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording / reproducing apparatus for an MR head, which is useful for a magneto-resistive head (hereinafter referred to as an MR head), and particularly relates to a switching time for recording and reproducing. The present invention relates to a recording / reproducing apparatus for MR head, which is shortened.

[0002]

2. Description of the Related Art Conventionally, a hard disk drive (HD
As the reproducing head for D), an MR head is used in addition to the usual induction type head. This MR head is designed so that the resistivity of a magnetic thin film changes due to a magnetic field from a magnetic medium, and this resistance change is detected as a reproduction output voltage. Such an MR head has high output and low crosstalk. Since it has a characteristic that it has no speed dependence, it is widely used as a high-density recording / reproducing head for a digital audio tape recorder or the like.

Since the MR head is a reproducing head, when it is used as a recording / reproducing head, thin-film induction type recording heads are stacked or arranged on the same substrate, or they are combined heads, or integrated with an independent recording head. It is designed to be used.

Various structures of such an MR type head are known, and for example, a shield type MR head as shown in FIG. 10 is known.

In the shield type MR head shown in FIG. 10, an MR element 13 is placed in a gap 12 sandwiched between shield cores 11 and 11 and is integrated with a signal conductor 14. The conductor 15 is also arranged in the gap 12, and the MR element 13 directly picks up the signal magnetic field from the magnetic medium.

Besides such a current bias type MR head, an MR head such as a shunt bias type which does not require the bias conductor 15 is also known. In this MR head, a magnetic field is applied by the MR current itself flowing through the signal conductor 14.

As shown in FIG. 11, the reproducing circuit of the above-mentioned current bias type MR head 1 has a structure in which an MR element 13 and a current source 2 are provided.
Flow an MR current from the
The resistance change of the R element 13 is taken out as a voltage, and a bias current is supplied from the bias current source 16 to the bias conductor 15 so as to apply a bias magnetic field to the MR element 13 for linearly operating the MR element 13. .

The bias conductor 15 and the MR element 13 are grounded at one end, and the voltage from the MR element 13 is supplied to the regenerative amplifier 4 as an unbalanced output through the DC blocking capacitor 3 and amplified. .

The capacitance of the DC blocking capacitor 3 is selected so as to allow the input signal waveform to pass therethrough without reducing the error rate, and is selected to be approximately 0.01 μF to 0.1 μF depending on the bit rate.

Further, in the case of the above-mentioned shunt bias type MR head or the like, the reproducing circuit which is exactly the same as that in FIG. 11 is constructed except that the bias current source 16 and the bias conductor 15 are not provided.

As such a recording / reproducing apparatus for an MR head, the present applicant has previously made the first-stage transistor 5 of the reproducing amplifier 4 a grounded base type (common base) as shown in FIG.
The MR element 13 of the R head 1 is connected between the emitter of the first-stage transistor 5 and the ground, the collector is connected through a load resistor 6 to a Vcc voltage source whose one end is grounded, and is taken out from the connection point of the collector and the load resistor 6. The collected collector voltage is compared with the reference voltage V _ref of the reference voltage source 7, and is amplified by a differential amplifier (voltage input-current output amplifier: hereinafter referred to as gm amplifier) 8. The output current of the gm amplifier 8 is Capacitor 9 for low pass filter (hereinafter referred to as LPF) determined by gm of the gm amplifier 8 and the value of the capacitor 9.
Is supplied to. The AC component is passed by this capacitor 9 and is fed back to the base of the first stage transistor 5 as a base current I _B.

The cutoff frequency of the above-mentioned LPF is determined by the following equation, and fc is kept sufficiently low (for example, 100 KHZ or less), and in order to realize low power consumption, gm of the gm amplifier 8 is set.
Is kept low. The value C of the LPF capacitor 9 requires a relatively large capacitance of about 0.1 μF.

[Equation 1]

[0013]

Although the recording circuit of the recording head system is not shown in the MR head reproducing apparatus having the configuration shown in FIG. 12, the R / WIC circuit of the recording / reproducing circuit is in the recording mode or the reproducing mode. Is configured to reduce power consumption in the R / WIC as much as possible by turning off one mode while turning off the other mode. Therefore, in the reproducing or recording mode of the reproducing apparatus for the MR head as shown in FIG. 12, it is necessary to turn on and off the reproduction amplifier 4 and the gm amplifier 8 which are the first-stage transistors 5 in the R / WIC.

FIG. 13 shows reproduction of R / WIC operation mode.
13 shows a timing waveform of the MR head reproducing apparatus shown in FIG. 12 when switching from recording to reproduction. The figure shows a case where the transistor 5 and the gm amplifier 8 in the first stage are simultaneously turned “on” and “off”.

In FIG. 13, FIG. 13A shows a switching signal obtained from the R / WIC, which is a reproduction mode “1” and a recording mode “0”.
Is done.

In FIG. 13B, the solid line shows the output signal V _C1 of the first-stage transistor 5, and the broken line shows the reference voltage output signal V _ref1 of the reference voltage source 7 supplied to the gm amplifier 8. In this case, the rise or fall of the gm amplifier 8 differs from that of the first-stage transistor 5 depending on the current capacity difference, and the first-stage transistor 5 rises and falls earlier. Therefore, as shown in FIG. 13B, a level difference ΔV is generated between the output signal V _C1 of the transistor 5 and the reference voltage output signal V _ref1 .

When such a level difference ΔV occurs, the gm amplifier 8 detects this level difference ΔV, and this voltage difference ΔV.
To convert the current into a current and pass it through the LPF capacitor 9 in FIG.
The output signal V _gm of the gm amplifier 8 shown in FIG.
As in D, the currents I _C1 and I _C2 are passed through the LPF capacitor 9.

When the recording mode is switched to the reproduction mode and the "on" state, the LPF capacitor 9 is charged with the excess charge slowly after the first-stage transistor 5 and the gm amplifier 8 are completely activated. FIG.
After the recording mode / playback mode switching time T _RW shown in D has elapsed, the switching from recording to playback is completed. The recording mode / reproduction mode switching time T _RW differs depending on the value of the LPF capacitor 9, but this value is as large as about 0.1 μF as described above, and is at the minimum value of several μs.
There was a problem that caused the delay.

The present invention provides a recording / reproducing apparatus for an MR head in which the above problems are solved. The first object of the present invention is, as described above, the first stage transistor 5 of the reproducing amplifier 4.
The gm amplifier 8 operates in a state where is not rising, and an erroneous current flows into the LPF capacitor 9 to be charged, and as a result, the reproduction output causes a DC level fluctuation,
It takes a long time to converge to a predetermined value, and a portion on which a head passes on a recording medium such as a hard disk during this period is a useless area in which recording cannot be performed, and the recording capacity is prevented from decreasing by that amount. An object of the present invention is to provide an MR head recording / reproducing apparatus which shortens the switching time of recording → reproducing mode or reproducing → recording mode in order to reduce the waste of the recording area on the recording medium.

The second object of the present invention is the MR shown in FIG.
A charging / discharging means for rapidly charging or discharging the DC blocking capacitor 3 interposed between the head 1 and the first stage regenerative amplifier 4 or the LPF capacitor 9 connected to the output stage of the gm amplifier 8 shown in FIG. An object of the present invention is to provide a recording / reproducing apparatus for an MR head which is provided and has a short switching time.

[0021]

A recording / reproducing apparatus for an MR head according to a first aspect of the present invention, as an example thereof is shown in FIG. 1, is a first stage of amplifying means for amplifying an output signal of the MR head 1. The amplifier 4 outputs the output signal of the MR head 1 and the reference voltage V
_In an MR head recording / reproducing device configured to feed back the DC component of the output of the differential amplifier 8 that amplifies the difference from _ref , the ON / OFF timings of the differential amplifier 8 and the first stage amplifier 4 are deviated from each other. The control means 24 for controlling the above is provided.

As shown in FIGS. 2 and 5, the MR head recording / reproducing apparatus of the present invention uses the output signal of the MR head 1 as the first stage amplifier among the amplifying means for amplifying the output signal of the MR head 1. In a recording / reproducing apparatus for an MR head, in which a direct current component of an output of a differential amplifier 8 for amplifying a difference from a reference voltage V _ref is fed back through a low-pass filtering capacitor 9, a low-pass filtering is performed. The output current of the differential amplifier 8 is changed when the capacitor 9 is rapidly charged and discharged.

The MR head recording / reproducing apparatus of the third aspect of the present invention, as shown in FIGS. 3 and 4, shows an amplifying means for amplifying the output signal of the MR head 1 through the DC blocking capacitor 3. The first stage amplifier 4 among them has a differential amplifier 8 for amplifying the difference between the output signal of the MR head 1 and the reference voltage V _ref.
In the MR head recording / reproducing device for feeding back the direct current component, the output current of the differential amplifier 8 is changed when the direct current blocking capacitor 9 is rapidly charged and discharged.

[0024]

According to the first MR head recording / reproducing apparatus of the present invention, the current source supplied to the base of the initial stage transistor 5 of the reproducing amplifier 4 and the current source of the gm amplifier 8 are individually controlled by the control circuit 24. Therefore, the switching time from the reproduction mode (recording mode) to the recording mode (reproduction mode) is significantly shortened, and a recording area on the recording medium can be recorded without waste.

According to the second MR head recording / reproducing apparatus of the present invention, the DC blocking capacitor 3 interposed between the MR head 1 and the initial stage reproducing amplifier 4 or the LPF capacitor 9 connected to the output stage of the gm amplifier 8 is used. Since the charging / discharging means 8A and 25 for rapidly charging / discharging the device are provided, it is possible to obtain the amplifier whose rise time and head switching time can be shortened.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the recording / reproducing apparatus for MR head of the present invention will be described in detail below with reference to FIGS.

FIG. 1 shows a circuit diagram of an embodiment in which the first stage transistor of the recording / reproducing apparatus for MR head of the present invention constitutes a grounded base amplifier, and the portions corresponding to those in FIG. There is.

In FIG. 1, the NP constituting the first stage regenerative amplifier 4
The N-type first-stage transistor 5 is a grounded-base amplifier, and since the MR element 13 of the MR head 1 is connected between the emitter and the ground, the conventional first-stage transistor of the common-emitter amplifier configuration shown in FIG. MR element 1 like
DC blocking capacitor 3 with a relatively large capacity between
Does not need

The base of the first-stage transistor 5 has a current source 22 for supplying a base voltage and a P for switching.
The NP transistor 21 as well as the first switching means 26
Is connected to the connection point between the emitter and the emitter, the collector of the PNP transistor is grounded, and the base has a first gm described later.
The direct current signal is fed back from the amplifier 8.

Further, the collector of the first-stage transistor 5 is connected to the Vcc voltage source via the load resistor 6 and also to the inverting input terminal of the first gm amplifier 8 which is a voltage input-current output differential amplifier.

The reference voltage V _ref is supplied from the reference voltage source 7 to the non-inverting input terminal of the first gm amplifier 8. Reference numeral 20 is a differential amplifier for extracting the output, which is the first gm amplifier 8
The input terminals are connected to the non-inverting and inverting input terminals of.

The output of the first gm amplifier 8 is grounded via the LPF capacitor 9, and the AC component of the reproduced signal is passed and the DC component is the PNP transistor 2 for switching.
This PNP transistor 2 is biased to the base of 1
Turn 1 on and off. This gm amplifier includes a current source 23 and a second switching means 2 as will be described later with reference to FIG.
Have 7.

In this example, in order to turn on / off the current sources 22 and 23 for the base currents of the gm amplifier 8 and the first-stage transistor 5 by the control circuit 24, which will be described later with reference to FIG. 3, provided in the R / WIC. The first and second switching means 26 and 27 are suppressed.

The first gm amplifier 8 is an NP as shown in FIG.
N made transistors Q ₁ and the under normal differential amplifier configuration consists of Q _2, the reference voltage V _ref1 from the reference voltage source 7 to the base of the transistor Q ₁ is fed, first stage transistor 5 to the base of the transistor Q ₂ The reproduction signal output, which is the voltage V _C1 across the load resistor 6 connected to the collector of, is supplied. The emitters of the transistors Q ₁ and Q ₂ are connected to each other, and the output of the control circuit 24 controls the switching means 27 provided between the emitter and the ground and the switching means 27 in the series circuit of the current source 23.

The control circuit 24 is an R / WIC as shown in FIG.
A switching signal R provided in the circuit and used in the reproduction or recording mode.
Circuit 30 for delaying / W by about 200 to 300 ns
The delayed signal supplied to the input terminal of each of the AND gate circuit 31 and the OR gate circuit 32, and
The switching signal R / W which is not delayed is directly AND gate circuit 3
1 and the other input terminal of the OR gate circuit 32 to supply the output of the AND gate circuit 31 to the output terminal T ₁ and the output of the OR gate circuit 32 to the output terminal T ₂ . The output of the output terminal T ₁ controls the switching means 27 “on” and “off”, and the output of the output terminal T ₂ controls the switching means 26 “on” and “off”.

The MR having the configuration described in detail with reference to FIGS. 1 to 3 above.
The operation of the head recording / reproducing apparatus will be described with reference to the time chart of FIG.

FIG. 4A shows the switching signal R / W supplied from the R / WIC to the control circuit 24, which is "1" in the reproduction mode.
It is “0” in the recording mode.

Such a switching signal R / W is supplied to the delay circuit 30 shown in FIG. 3 so that the delay time ΔT = 200 ns to 300 ns.
It is delayed by about ns to obtain the ΔT delay waveform as shown in FIG. 4B.

At the time of switching from the reproduction mode to the recording mode, before the output signal V _C1 of the first-stage transistor 5 and the level of the reference voltage source 7 are deviated by ΔV as shown in FIG. 13, first the first gm amplifier 8 is set as shown in FIG. 4D. The output signal of the AND gate circuit 31 in the control circuit 24 turns off the switching means 27.
Let Then, after about ΔT = 200 ns, the switching means 26 is turned “off” by the output signal of the OR gate circuit 32 in the control circuit 24, as shown in FIG. 4C. The value of ΔT in this case is the first gm amplifier 8
Is about 200 ns, since it may be longer than the time until it is completely turned off.

When the recording mode "0" is switched to the reproducing mode "1" as shown in FIG. 4A, conversely, the first-stage transistor 5 of the first-stage reproducing amplifier 4 is replaced with the OR gate circuit 32 in the control circuit 24 as shown in FIG. 4C. After about .DELTA.T = 300 ns has passed since the switching means 26 was turned "on" by the output signal of FIG. 4, the first gm amplifier 8 is turned on by the output of the AND gate circuit 31 as shown in FIG. 4D. The delay time ΔT in this case is approximately 300 ns because it may be longer than the time required for the output of the first-stage transistor 5 and the reference voltage V _ref1 of the reference voltage source 7 to stabilize.

As described above, when the operation mode such as recording mode → reproduction mode or reproduction mode → recording mode is changed, “ON”
Since the unnecessary currents I _C1 and I _C2 flowing through the LPF capacitor 9 can be avoided by shifting the “OFF” timing, the recording mode → reproduction mode switching time can be ideally shortened to about ΔT.

In the MR head recording / reproducing apparatus described above, the first
Of the LPF capacitor 9 connected to the output stage of the gm amplifier 8 or the DC blocking capacitor 3 interposed between the MR head 1 described in the conventional configuration of FIG. It takes a large value. Therefore, in order to start up the first-stage transistor 5, the LPF capacitor 9 or the DC blocking capacitor 3 must be charged to a predetermined potential. Further, since the resistance value and the optimum sense current when the MR head 1 is not operating vary depending on the MR head 1, the DC blocking capacitor 3 or the LPF capacitor 3 is switched when the MR head 1 is switched, for example, from the recording mode to the reproducing mode. The potential of 9 is large (several hundred m
v) It will change, and charging / discharging will be needed.

Since the charge / discharge current is supplied from the base current source in the conventional first stage transistor, the supply current is 10
Since it is 0 μA or less, it takes several ms for the startup time.

An MR head recording / reproducing apparatus which solves the above problems will be described with reference to FIGS.

FIG. 5 shows a circuit diagram when a grounded base amplifier is used for the first stage transistor.
Corresponding parts are designated by the same reference numerals and duplicate description will be omitted. That is, in the case of FIG. 5, the first gm amplifier 8 is a variable gain type gm amplifier 8A.

FIG. 6 shows a grounded base amplifier similar to that shown in FIG. 5, in place of the variable gain type gm amplifier 8A.
As the m-amplifier 8, a small gm is selected, and the gm is made larger than that of the first gm-amplifier 8.
The second gm amplifier 2 capable of rapidly charging and discharging the capacitor 9
5 is selected and the output signal V _C1 of the first-stage transistor 5 is set to the first
And the inverting input terminals of the second gm amplifiers 8 and 25 to supply the reference voltage V _ref1 of the reference voltage source 7 to the first and second gm amplifiers.
It is supplied to the non-inverting input terminals of the m amplifiers 8 and 25, and the outputs of the first and second gm amplifiers 8 and 25 are commonly connected to L
It is configured to be connected to the PF capacitor 9 and to perform DC feedback to the base of the first stage transistor 5.

FIG. 7 shows a case where the first-stage transistor 5 of the regenerative amplifier 4 has a grounded-emitter amplifier structure, and the MR head 1 has the same MR element 13 as that shown in FIG.
Is grounded at one end, and the other end is connected to the current source 2, and the change voltage of the resistance value due to the signal magnetic field taken out from the connection point of the current source 2 and the MR element 13 is passed through the DC blocking capacitor 3 to the first-stage transistor 5 The output of the variable gain type gm amplifier 8A similar to that shown in FIG. 5 is fed back to the connection point between the DC blocking capacitor 3 and the base of the first-stage transistor 5.

FIG. 8 is a modification of FIG. 5 in which the first gm amplifier 8 having a small gm and the second gm amplifier 25 having a large gm are used instead of the variable gain type gm amplifier 8A.

5 to 8 described above, the LPF capacitor 9 having a relatively large capacity and the DC blocking capacitor 3 are rapidly connected at the time of power-on, at the time of rising from the time of power saving, and at the time of head switching. When the variable gain type gm amplifier 8A is used, the first and second gm amplifiers 8 and 25 are controlled so as to increase gm similarly to the above-described operations. As in the case of each operation described above, the one used is switched to the side of the second gm amplifier 25 so as to shorten the rise time of the first-stage transistor 5 and the head switching time. In principle, FIGS. 8 is the same as that of FIG. 8, so this example will be described below with reference to the circuit diagram of FIG. 8 and the timing chart of FIG.

FIG. 8 shows the case where the first-stage transistor 5 has a grounded emitter, the MR element 13 is supplied with a sense current from the current source 2, and the MR element 13 of the MR head 1 changes in resistance due to the signal magnetic field from the magnetic medium. The head output, which has been converted into a voltage and passed through the DC blocking capacitor, is amplified by the first-stage transistor 5. The output signal V _C1 of the first-stage transistor 5 is compared with the reference voltage V _ref1 of the reference voltage source 7 by the first gm amplifier 8, the AC component is passed through the LPF capacitor 9, and the DC component is supplied to the base of the first-stage transistor 5. DC is fed back.

The LPF capacitor 9 and the gm of the first gm amplifier 8 determine the cutoff frequency fc of the LPF. Since this fc is determined by the equation 1 as described above,
If fc is low (100 KHZ or less) and gm is kept low to reduce power consumption, the capacitance C of the LPF capacitor 9 becomes a large value of 0.1 μF. But the first gm
The current supply capacity of the amplifier 8 is 100 μA or less, and the time for charging / discharging the LPF capacitor 9 or the DC blocking capacitor 3 for starting the amplifier and switching the head is several μs.

Then, as shown in FIGS. 9A and 9B, when the power source is turned on and the head is switched from head (0) to head (1) and the first gm amplifier is turned on as shown in FIG. the time period T ₁ or T ₂ required as shown second high gm amplifier 25 to such to "on".

When the second gm amplifier 25 is constantly operated, unnecessary power consumption is increased, and the large gm of the second gm amplifier 25 increases the cut-off frequency fc of the LPF, which causes reproduction. Since the frequency characteristic of the amplifier is destroyed, it is possible to temporarily turn on and off the gm amplifier 25.

In FIG. 9, the time T ₁ , T ₂ during which the second gm amplifier 25 is “on” is the magnitude of the capacitor 9 or 3.
It is determined in consideration of the resistance value of the MR element of the MR head 1 and the sense current flowing in the MR head 1.

Although a circuit for actually controlling "on" and "off" is not shown in FIGS. 5 to 8, even if the CPU or the like provided in the R / WIC counts the actual time,
Alternatively, it is obvious that the output of the second gm amplifier 25 may be monitored and the output thereof may be "on" or "off" controlled. In the case of the variable gain type gm amplifier 8A described with reference to FIGS. 5 and 7, the times T ₁ and T ₂ shown in FIG. 9D are used.
It is obvious that the control may be performed in the high gm state during the period.

[0056]

According to the first aspect of the recording / reproducing apparatus for the MR head of the present invention, the switching time of the recording mode → reproducing mode or the reproducing mode → recording mode is shortened, and the wasted area of the recording area on the recording medium is reduced. Can be done less. Further second
According to the invention, it is possible to obtain the one in which the rise time of the first stage transistor is shortened when the power is turned on or the head is switched.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a recording / reproducing apparatus for an MR head of the present invention.

FIG. 2 is a graph showing a recording / reproducing apparatus for MR head of the present invention.
It is a circuit diagram which shows one Example of an m amplifier.

FIG. 3 is a circuit diagram showing an embodiment of a control circuit used in the MR head recording / reproducing apparatus of the present invention.

FIG. 4 is a timing chart of the circuit shown in FIG. 1 of the MR head recording / reproducing apparatus of the present invention.

FIG. 5 is a circuit diagram showing an example in which the first stage transistor of the MR head recording / reproducing apparatus of the present invention has a grounded base.

FIG. 6 is a circuit diagram showing another example in which the first-stage transistor of the MR head recording / reproducing apparatus of the present invention has a base grounded.

FIG. 7 is a circuit diagram showing an example in which the first-stage transistor of the MR head recording / reproducing device of the present invention has a grounded emitter.

FIG. 8 is a circuit diagram showing another example in which the first-stage transistor of the MR head recording / reproducing apparatus of the present invention has a grounded emitter.

9 is a timing chart of the circuit shown in FIG. 8 of the recording / reproducing apparatus for an MR head of the present invention.

FIG. 10 is a configuration diagram of a conventional shield type MR head.

FIG. 11 is a system diagram of a conventional MR head recording / reproducing apparatus.

FIG. 12 is another circuit diagram of a conventional MR head recording / reproducing apparatus.

FIG. 13 is a circuit timing chart shown in FIG. 12 of a conventional MR head recording / reproducing apparatus.

[Explanation of symbols]

 1 MR head 5 First stage transistor 6 Load resistance 7 Reference voltage source 8 First gm amplifier 8A Variable gain type gm amplifier 9 LPF capacitor 22,23 Current source 24 Control circuit 25 Second gm amplifier 26,27 Switching means

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[Procedure amendment]

[Submission date] February 1, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0022

[Correction method] Change

[Correction content]

As shown in FIGS. 5 and 6 , the recording / reproducing apparatus for MR head according to the second aspect of the present invention has an MR amplifier for amplifying an output signal of the MR head 1 as an initial stage amplifier.
In a recording / reproducing apparatus for an MR head, a direct current component of an output of a differential amplifier 8 for amplifying a difference between an output signal of the head 1 and a reference voltage V _ref is fed back via a low pass filtering capacitor 9. The output current of the differential amplifier 8 is changed when the low-pass filtering capacitor 9 is rapidly charged and discharged.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0023

[Correction method] Change

[Correction content]

The MR head recording / reproducing apparatus according to the third aspect of the present invention has an amplifying means for amplifying the output signal of the MR head 1 through the DC blocking capacitor 3 as shown in FIGS. 7 and 8 . The first stage amplifier 4 among them has a differential amplifier 8 for amplifying the difference between the output signal of the MR head 1 and the reference voltage V _ref.
In the MR head recording / reproducing device for feeding back the direct current component, the output current of the differential amplifier 8 is changed when the direct current blocking capacitor 9 is rapidly charged and discharged.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0030

[Correction method] Change

[Correction content]

Further, the collector of the first-stage transistor 5 is connected to the Vcc voltage source via the load resistor 6 and also to the non- inverting input terminal of the first gm amplifier 8 which is a voltage input-current output differential amplifier. Connected.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0031

[Correction method] Change

[Correction content]

The reference voltage V _ref supplied from the reference voltage source 7 to the inverted input terminal of the first gm amplifier 8. Reference numeral 20 denotes a differential amplifier for taking out an output, the input terminals of which are connected to the non-inverting and inverting input terminals of the first gm amplifier 8.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Name of item to be corrected] 0032

[Correction method] Change

[Correction content]

The output of the first gm amplifier 8 is grounded via the LPF capacitor 9, and the AC component of the reproduced signal is passed and the DC component is the PNP transistor 2 for switching.
Returned to the base of 1 . This gm amplifier has a current source 23 and a second switching means 27 as will be described later with reference to FIG.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0033

[Correction method] Change

[Correction content]

In this example, in order to turn on / off the current sources 22 and 23 for the base currents of the gm amplifier 8 and the first-stage transistor 5 by the control circuit 24, which will be described later with reference to FIG. 3, provided in the R / WIC. It controls the first and second switching means 26 and 27.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0034

[Correction method] Change

[Correction content]

An example of the first gm amplifier 8 is shown in FIG. The reference voltage V _ref1 from the reference voltage source 7 is supplied to the base of the transistor Q ₁ , and the output current Io is supplied from the collector Vo of the first stage transistor 5 to the base of the transistor Q ₂ . The emitters of the transistors Q ₁ and Q ₂ are 2
The output of the control circuit 24 controls the switching means 27 in the series circuit of the current source 23 and the switching means 27 connected between the two resistances and between the two resistances and the ground. The collectors of the transistors Q ₁ and Q ₂ are
The collectors of the transistors Q ₃ and Q ₄ are connected,
The collector and base of transistor Q ₃ are connected in common.
In addition, the bases of the transistors Q ₃ and Q ₄ are the same.
And the collectors of transistors Q ₃ and Q ₄ are electrically connected.
It is connected to the pressure source Vcc. This is the transistor Q ₄
The output current Io is output to Vo via the inductor.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0042

[Correction method] Change

[Correction content]

In the MR head recording / reproducing apparatus described above, the first
Of the LPF capacitor 9 connected to the output stage of the gm amplifier 8 or the DC blocking capacitor 3 interposed between the MR head 1 described in the conventional configuration of FIG. It takes a large value. Therefore, in order to start up the first-stage transistor 5, the LPF capacitor 9 or the DC blocking capacitor 3 must be charged to a predetermined potential. Furthermore, MR resistance and optimum sense current potential of the MR at DC blocking capacitor head 1 example cut conversion 3 or LPF capacitor 9 for get rose by MR head 1 in the non-operation of the head 1 is large (hundreds mv ) It will change, and charging and discharging will be required.

[Procedure Amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0043

[Correction method] Change

[Correction content]

In the conventional example (FIG. 12) , the charge / discharge current is supplied from the gm amplifier 8. However, since the gm is small, the supply current is 100 μA or less , and the startup time is several ms.
Need time.

[Procedure Amendment 10]

[Document name to be amended] Statement

[Correction target item name] 0046

[Correction method] Change

[Correction content]

FIG. 6 shows a grounded base amplifier similar to that shown in FIG. 5, in place of the variable gain type gm amplifier 8A.
As the m-amplifier 8, a small gm is selected, and the gm is made larger than that of the first gm-amplifier 8.
The second gm amplifier 2 capable of rapidly charging and discharging the capacitor 9
5 is selected and the output signal V _C1 of the first-stage transistor 5 is set to the first
And the second is supplied to the non-inverting input terminal of the gm amplifier 8 and 25, supplies a reference voltage V _ref1 of the reference voltage source 7 to the inverted input terminal of the first and second gm amplifiers 8 and 25, the first And the outputs of the second gm amplifiers 8 and 25 are commonly connected to L
It is configured to be connected to the PF capacitor 9 and to perform DC feedback to the base of the first stage transistor 5.

[Procedure Amendment 11]

[Document name to be amended] Statement

[Correction target item name] 0051

[Correction method] Change

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The LPF capacitor 9 and the gm of the first gm amplifier 8 determine the cutoff frequency fc of the LPF. Since this fc is determined by the equation 1 as described above,
If fc is low (100 KHZ or less) and gm is kept low to reduce power consumption, the capacitance C of the LPF capacitor 9 becomes a large value of 0.1 μF. But the first gm
Current supply capability of the amplifier 8 is a 100μA or less, the time for charging and discharging the LPF capacitor 9 or DC blocking capacitor 3 in the launch and head switching amplifier comprising a number m s.

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[Name of item to be corrected] Figure 1

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[Figure 1]

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[Name of item to be corrected] Figure 2

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[Fig. 2]

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[Name of item to be corrected] Figure 5

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[Figure 5]

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[Name of item to be corrected] Figure 6

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[Figure 6]

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[Name of item to be corrected] Figure 7

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[Figure 7]

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[Correction target item name] Figure 8

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[Figure 8]

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[Name of item to be corrected] Fig. 12

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[Fig. 12]

Claims (10)

[Claims] 1. A direct current of an output of a differential amplifier for amplifying a difference between an output signal of the magnetoresistive head and a reference voltage in an initial stage amplifier of an amplifying means for amplifying an output signal of the magnetoresistive head. A recording / reproducing apparatus for a magnetoresistive effect head, which is configured to feed back components, comprising control means for controlling ON / OFF timings of the differential amplifier and the first-stage amplifier so as to be shifted from each other. A recording / reproducing apparatus for a magnetoresistive head, which is characterized by: 2. The direct current component of the output of a differential amplifier for amplifying the difference between the output signal of the magnetoresistive head and the reference voltage in the first stage amplifier of the amplifying means for amplifying the output signal of the magnetoresistive head. In a recording / reproducing device for a magnetoresistive effect head, in which is fed back through a low-pass filtering capacitor, the output current of the differential amplifier is changed when the low-pass filtering capacitor is rapidly charged and discharged. A recording / reproducing apparatus for a magnetoresistive effect type head, which is configured to be variable. 3. A differential amplifier for amplifying the difference between the output signal of the magnetoresistive head and the reference voltage in the first stage amplifier of the amplification means for amplifying the output signal of the magnetoresistive head via the DC blocking capacitor. In a head recording / reproducing device for a magnetoresistive effect in which a direct current component of a dynamic amplifier is fed back, an output current of the differential amplifier is changed when the direct current blocking capacitor is rapidly charged and discharged. A recording / reproducing apparatus for a magnetoresistive head, which is characterized in that 4. The control means is configured to turn off the differential amplifier first when the magnetoresistive head is switched from the reproducing state to the recording state and turn off the first stage amplifier after a predetermined time. A recording / reproducing apparatus for a magnetoresistive head according to claim 1. 5. The control means is configured such that, when the magnetoresistive head is switched from the recording state to the reproducing state, the first stage amplifier is turned on first, and the differential amplifier is turned on after a predetermined time. The recording / reproducing apparatus for a magnetoresistive head according to claim 1, which is characterized in that. 6. The magnetoresistive head recording / reproducing apparatus according to claim 1, wherein the first stage amplifier is a grounded base amplifier. 7. The magnetoresistive head recording / reproducing apparatus according to claim 1, wherein the first-stage amplifier is a grounded-emitter amplifier. 8. The magnetoresistive effect according to claim 2, wherein the differential amplifier for varying the output current is configured to switch and output two differential amplifiers according to the magnitude of gain. Recording / playback device for mold head. 9. The magnetoresistive head recording / reproducing apparatus according to claim 2, wherein the first stage amplifier is a grounded base amplifier. 10. The magnetoresistive head recording / reproducing apparatus according to claim 3, wherein the first-stage amplifier is a grounded-emitter amplifier.