JPH07202575A - Waveform shaping circuit for analog signal - Google Patents

Abstract

PURPOSE:To provide the waveform shaping circuit for analog signal simplifying the post processing by correcting the positive and negative asymmetry for the reference level of an input signal in the magnetic recording demodulation device or the like using the MR head on the waveform shaping circuit for analog signal. CONSTITUTION:The waveform shaping circuit matching the positive and negative amplitude of an alternating analog signal with dissimilar positive and negative amplitude for the level 0 being the reference consists of a means 1 detecting the positive and negative maximum amplitude value, correction amount arithmetic means 2 calculating the correction amount so as to match the amplitude for the reference level of the analog signal from the detection value of the means 1, and amplitude correction means 3 correcting the amplitude of the analog signal according to the arithmetic correction amount by the means 2. In the magnetic disk, the positive and negative amplitude of the read waveform of the MR head can be matched and the conventional demodulation circuit can be used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveform shaping circuit for analog signals, and more particularly, for analog signals having different positive and negative amplitudes which should be the same, the amplitude of the positive signal from the reference 0 level and the amplitude of the negative signal are matched. The present invention relates to an analog signal waveform shaping circuit for shaping and correcting a waveform so that the waveform is corrected.

Conventionally, in a magnetic disk apparatus, information recorded on a magnetic disk with the maximum positive and negative amplitudes being the same with respect to a reference 0 level is recorded on a magnetoresistive head (M
When read using the (R head), the maximum positive and negative amplitudes with respect to the 0 level are different, so that the circuit configuration for demodulating the reproduced signal from the MR head is complicated. A magnetic disk device using an MR head that can be simplified is desired.

[0003]

2. Description of the Related Art In recent years, a high-performance magnetic head has been required as the capacity of a magnetic disk device, which is an external storage device of a computer, has increased. To satisfy this requirement,
In place of the conventional inductive head whose output characteristic changes according to the speed of the recording medium, an MR head that can obtain a high output without depending on the speed of the recording medium is drawing attention.

This MR head requires a bias for tilting the direction of magnetization of the magnetoresistive film in order to improve the linear response of the element. By properly performing this bias, the performance of the MR head is improved. can do.
Such an MR head has a Co type amorphous soft magnetic film (CoZr) close to a magnetoresistive effect film (abbreviated as MR film).
The magnetic field from the magnetized CoZr film is
A bias magnetic field is applied to the R film. This is because, in order to put a magnetic head utilizing the magnetoresistive effect into practical use, the direction of magnetization of the MR film is set to 4 degrees from the magnetic recording medium surface.
This is because it is necessary to incline about 5 ° to improve the response sensitivity and the linearity of the element. Inclining the direction of magnetization of this MR film is called a bias, and various methods have been proposed.

[0005]

However, such an MR head has a problem in that the MR of the head is affected by the magnetization on the medium.
Since the magnetic resistance of the element is converted to voltage, in the region where the relationship between the magnetization on the medium and the magnetic resistance of the head is not linear, the amplitude of the output waveform has positive and negative asymmetry with respect to the reference level. When demodulating such a waveform, there is a problem that a demodulation error is likely to occur when trying to detect peaks, for example. Then, if it is attempted to take measures against this, a new circuit is required, the circuit configuration becomes complicated, and the cost increases.

Since the reproduced waveform of the conventional inductive head has no positive or negative asymmetry with respect to the reference level,
The above-described processing was not required in the magnetic recording / reproducing apparatus. Therefore, in the magnetic recording demodulation device using the MR head, the present invention uses a simple circuit to correct the positive / negative asymmetry with respect to the reference level of the reproduction waveform in the preceding stage of the reproduction waveform demodulation circuit. An object of the present invention is to provide a waveform shaping circuit for an analog signal, which can use the same one as the reproduction processing circuit of the inductive head and can reduce the cost.

[0007]

FIG. 1 shows the principle configuration of an analog signal waveform shaping circuit of the present invention for achieving the above object. The present invention is a circuit that shapes a waveform so that positive and negative amplitudes of an AC analog signal whose positive and negative amplitudes are different with respect to a reference 0 level are the same, and has a maximum positive and negative amplitude value as shown in FIG. The detecting means 1 detects the positive and negative maximum amplitude values with respect to the reference level of the input analog signal,
The correction amount calculation means 2 calculates a correction amount for equalizing the amplitude of the analog signal with respect to the reference level from the detection values of the positive and negative maximum amplitude value detection means 1, and the amplitude correction means 3 calculates the correction amount. The amplitude of the analog signal is corrected according to the correction amount calculated by the means 2.

Then, the amplitude correcting means 3 is branched by a signal branching means for dividing the analog signal into a positive signal having a level on the positive side of the 0 level and a negative signal having a level on the negative side. It can be configured by including a correction unit that performs amplification correction or attenuation correction on at least one of the positive signal and the negative signal, and a signal combining unit that combines the corrected signals.

The amplitude correction means 3 includes a signal extraction means for extracting a positive signal having a level on the positive side of the 0 level or a negative signal having a level on the negative side from the analog signal, and the extracted positive signal. It may be configured to include a correction unit that performs amplification correction or attenuation correction on a signal or a negative signal, and a signal combining unit that combines the corrected signal with the original signal.

Further, the amplitude correction means 3 converts the analog signal into three signals, a positive signal having a level on the positive side of the 0 level, a negative signal having a level on the negative side, and a signal as it is. Signal dividing means for dividing, correction means for performing amplification correction or attenuation correction on at least one of the branched positive signal and negative signal, and signal combining means for combining the corrected signal with the original analog signal. It is also possible to configure with and.

[0011]

According to the analog signal waveform shaping circuit of the present invention, the deviation between the positive and negative amplitudes of the input analog signal with respect to the reference level is obtained, and at least two reproduction signals from the MR head are branched according to this deviation. Then, after correcting the deviation of the positive and negative amplitudes with respect to the reference level in the branch circuit, the signals flowing through the branch circuit are combined.
As a result, the reproduced signal after synthesis has the same positive and negative amplitude with respect to the reference level. Therefore, if this analog signal waveform shaping circuit is applied to a magnetic disk device in which a MR head reproduces a signal having the same positive and negative amplitude with respect to a reference level recorded in advance on a magnetic disk, the analog signal is shaped with respect to the reference level. Since the positive and negative amplitudes of the signals having positive and negative amplitude deviations are the same, a circuit having the same structure as the demodulating circuit of the inductive head can be used for the demodulating circuit.

[0012]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the embodiment described here, data is read from a magnetic disk 7 by using an MR head 8 as a waveform shaping circuit for analog signals. A reproducing system of a magnetic disk device for reading will be described as an example. In addition, the magnetic disk 7,
It is assumed that the training signal writing circuit 5 writes a sine wave whose positive and negative amplitudes are symmetrical by the inductive head 6 by the training signal writing circuit 5 in the servo area before the data area. Therefore, when the training signal is read using the inductive head, a waveform having positive and negative amplitudes symmetrical to each other is obtained, but when read using the MR head 6, a waveform having different positive and negative amplitudes is obtained. Will be obtained.

FIG. 2A shows the configuration of the analog signal waveform shaping circuit 10 according to the first embodiment of the present invention. The input signal is read from the magnetic disk 7 by the MR head 8. The signal amplified by the head IC 9 is used. The analog signal waveform shaping circuit 10
Two rectifier circuits 11 and 12, changeover switches SWP and SW
N, positive / negative maximum amplitude detection circuit 13, correction amount calculation circuit 1
4, an amplifier / attenuator 21 having an amplification function and an attenuation function, and an adder 27.

The input signal is bifurcated into two rectifier circuits 11, 1.
2 are input respectively. The rectifier circuit 11 outputs only the positive component of the input signal, and the rectifier circuit 12 outputs only the negative component of the input signal. The changeover switches SWP and SWN are connected to the output sides of the rectifier circuits 11 and 12, respectively, and the changeover switch SWP is equivalent to the rectifier circuit 1
The output of 1 is input to either the positive / negative maximum amplitude detection circuit 13 or the amplifier / attenuator 21. The changeover switch SWN is linked to the changeover switch SWP. When the changeover switch SWP inputs the output of the rectifying circuit 11 to the positive and negative maximum amplitude detecting circuit 13, the rectifying circuit 12 simultaneously.
Is input to the positive and negative maximum amplitude detection circuit 13, and the changeover switch SWP amplifies and amplifies the output of the rectifier circuit 11.
When 1 is input, the output of the rectifier circuit 12 is input to the adder 27.

The positive / negative maximum amplitude detection circuit 13 detects the maximum amplitude value of the positive signal input from the rectifier circuit 11 and the maximum amplitude value of the negative signal input from the rectifier circuit 12,
This is output to the correction amount calculation circuit 14. The correction amount calculation circuit 14 outputs to the amplifier / attenuator 21 a control signal that makes the maximum values of the amplitudes of the positive / negative signals input from the positive / negative maximum amplitude detection circuit 13 the same, and outputs the control signal to the amplifier / attenuator 21. Determine the gain. That is, when the amplitude of the positive signal is larger than the amplitude of the negative signal, a negative gain is set in the amplifying / attenuating device 21 to cause the amplifying / attenuating device 21 to function as an attenuator, and conversely, a positive gain. If the amplitude of the signal is smaller than the amplitude of the negative signal, a positive gain is set in the amplifier / attenuator 21 to cause the amplifier / attenuator 21 to function as an amplifier.

The operation of the analog signal waveform shaping circuit 10 configured as described above will be described with reference to FIG. 2B when the amplitude of the negative signal is larger than that of the positive signal. In the magnetic disk 7, as described above, the training signal writing circuit 5 is provided in the servo area before the data area.
Thus, as shown by the waveform A at point A, it is assumed that the inductive head 6 has written a sine wave having a positive and negative amplitude symmetrical with the reference level as 0.

First, when the magnetic disk 7 is activated, the changeover switches SWP and SWN connect the rectifier circuits 11 and 12 to the maximum positive and negative amplitude detection circuit 13. In this state, the training signal is read from the MR head 8 and the head IC
It is amplified by 9 and becomes an input signal. As can be seen from the input signal at the point B, the amplitude of the positive signal is smaller than the amplitude of the negative signal (the dotted line shown in the waveform B at point B in FIG. 2 indicates the same amplitude value as the amplitude of the negative signal). . The positive component of the input signal is input to the positive and negative maximum amplitude detection circuit 13 through the rectifier circuit 11 and the changeover switch SWP, and the negative component is input to the positive and negative maximum amplitude detection circuit 13 through the rectifier circuit 12 and the changeover switch SWN. The maximum value of the amplitude of the signal is detected.

The correction amount calculation circuit 14 uses the maximum amplitude value data from the positive / negative maximum amplitude detection circuit 13 to determine the amplitude of the positive signal when the amplitude of the positive signal is smaller than the amplitude of the negative signal. Is increased to match the amplitude of the negative signal, and the gain is set so that the amplifier / attenuator 21 functions as an amplifier. In this way, the correction amount calculation circuit 1
When the gain of the amplifier / attenuator 21 is set by 4,
The changeover switches SWP and SWN are switched. After that, the input signal read by the MR head 8 and amplified by the head IC 9 is divided into positive and negative components by the rectifier circuits 11 and 12. Then, the positive signal is amplified by the amplifier / attenuator 21, has the same amplitude as the negative signal, is output to the point C in the figure as shown by the waveform C, and is added to the adder 27. Further, the negative signal from the rectifier circuit 12 is directly added to the adder 27. As a result, the adder 27 obtains the output signal indicated by the waveform D having the same positive and negative amplitudes.

The changeover switches SWP and SWN are switched to the positive and negative maximum amplitude detection circuit 13 side when the magnetic disk device is shipped from the factory, when the magnetic disk device is activated, or when a predetermined period elapses. Good at times,
At this time, the amplification / decision determined by the correction amount calculation circuit 14
The gain of the attenuator 21 may be fixed until it is changed next time.

FIG. 3A shows the rectifier circuits 11 and 1 in FIG.
2 shows a specific configuration of the comparator 2
1, a selector (+) 32 that outputs a positive polarity signal, and a selector (-) 33 that outputs a negative polarity signal. A threshold signal having a level of 0 for separating the positive side component and the negative side component of the analog input waveform is input to the comparator 31, and the pulse signal indicated by the waveform E is output from the comparator depending on whether the analog input signal is positive or negative.
This pulse signal is input to the selector (+) 32 and the selector (-) 33 as a clock. Selector (+) 32
The analog signal and the threshold signal are also input to the selector and the selector (−) 33, respectively, and when the output of the comparator 31 is at the high level “H”, the selector (+) 32 outputs the signal of the positive polarity to the selector (−). -) 33 outputs a threshold signal. On the other hand, the comparator 31
When the output of is at low level "L", the selector (+)
Threshold signal is output from 32, selector (-)
A signal of negative polarity is output from 33.

FIG. 4A shows the structure of the analog signal waveform shaping circuit 20 according to the second embodiment of the present invention. The same components as those of FIG. 2A are designated by the same reference numerals. It is attached. The analog signal waveform shaping circuit 20 of this embodiment is different from the analog signal waveform shaping circuit 10 of the embodiment of FIG. 2A in that the amplification / disposition circuit provided between the changeover switch SWP and the adder 27 is provided. There is no attenuator 21, and instead an amplifier / attenuator 22 is provided between the changeover switch SWN and the adder 27.
Is provided. Except for this point, the circuit configuration of FIG. 4 (a) is the same as the circuit configuration of FIG. 2 (a).
The description is omitted.

In the analog signal waveform shaping circuit 10 of FIG. 2 (a), the positive signal is adjusted to have the same amplitude as the negative signal by the amplifier / attenuator 21, but in this embodiment, the negative signal is amplified. Adjusted by attenuator 22 to the same amplitude as the positive signal. For example, when the negative signal at the point E in the diagram indicated by the waveform L is smaller than the positive signal at the point D in the diagram indicated by the waveform H in FIG. 4B, the amplifier / attenuator 22 functions as an amplifier. However, the amplitude of the signal at the point F indicated by the waveform N is the same as the amplitude of the signal at the point D. Therefore, the output waveform has a symmetrical waveform.

FIG. 5 (a) shows the structure of the analog signal waveform shaping circuit 30 of the third embodiment of the present invention, which has the same structure as the constituent members of FIGS. 2 (a) and 4 (a). The members have the same reference numerals. The analog signal waveform shaping circuit 30 of the third embodiment is different from the analog signal waveform shaping circuits 10 and 20 of the embodiments of FIGS. 2A and 4A in that the changeover switch S is used.
An amplifier / attenuator 21 is provided between the WP and the adder 27, and an amplifier / attenuator 22 is also provided between the changeover switch SWN and the adder 27. Except for this point, the circuit configuration of FIG. 5 (a) is the same as the circuit configuration of FIGS. 2 (a) and 4 (a), and the description thereof is omitted.

Further, in the analog signal waveform shaping circuit 10 of FIG. 2A, the positive signal is adjusted to have the same amplitude as the negative signal by the amplifier / attenuator 21, and the waveform of the analog signal of FIG. 4A is obtained. In the shaping circuit 20, the negative signal is adjusted to the same amplitude as the positive signal by the amplifier / attenuator 22, but in the third embodiment, both the positive and negative signals have the same amplitude due to the combined use of the amplifier / attenuators 21 and 22. Adjusted to. For example, Figure 5 (b)
When the negative signal at the point H in the figure indicated by the waveform w is smaller than the positive signal at the point G in the figure indicated by the waveform w, the amplifiers / attenuators 21 and 22 are both made to function as an amplifier to amplify the Amplification / attenuator 22 rather than gain of attenuator 21
If the gain of is increased, the amplitude of the positive signal and the amplitude of the negative signal can be made the same as indicated by the dotted line, and the output waveform f becomes a positive / negative symmetrical waveform.

FIG. 6A shows the configuration of the analog signal waveform shaping circuit 40 of the fourth embodiment of the present invention. The same reference numerals are given to the same components as those of FIG. 2A. It is attached. Analog signal waveform shaping circuit 40 of the fourth embodiment
Is a waveform shaping circuit 10 for analog signals of the embodiment of FIG.
2 is that the amplifier / attenuator 21 is replaced with an attenuator 23. Except for this point, the configuration of the circuit shown in FIG. 6A is the same as the configuration of the circuit shown in FIG.

In the analog signal waveform shaping circuit 40 of the fourth embodiment, the positive side component of the input signal is higher than the negative side component as shown by the waveform I at point I shown in FIG. 6 (b). The asymmetry can only be corrected for large signals. Therefore, in the analog signal waveform shaping circuit 40 of the fourth embodiment, the positive signal at the point J is attenuated by the attenuator 23 to the same amplitude as the negative signal, as shown by the waveform in FIG. 6 (b). The output signal has a positive and negative symmetrical waveform as shown by the waveform.

FIG. 7A shows the structure of an analog signal waveform shaping circuit 50 according to the fifth embodiment of the present invention. The same components as those of FIG. 4A are designated by the same reference numerals. It is attached. Analog signal waveform shaping circuit 50 of the fifth embodiment
Is a waveform shaping circuit 20 for analog signals of the embodiment of FIG.
2 is that the amplifier / attenuator 22 is replaced with an attenuator 24. Except for this point, the configuration of the circuit shown in FIG. 7A is the same as the configuration of the circuit shown in FIG.

In the analog signal waveform shaping circuit 50 of the fifth embodiment, the negative side component of the input signal is higher than the positive side component as shown in the waveform S at the point K shown in FIG. 7 (b). The asymmetry can only be corrected for large signals. Therefore, in the analog signal waveform shaping circuit 50 of the fifth embodiment, the negative signal at point L is attenuated by the attenuator 24 to the same amplitude as the positive signal, as shown by the waveform in FIG. 6 (b). , The output signal has a positive / negative symmetrical waveform as shown by the waveform "L".

FIG. 8A shows the structure of an analog signal waveform shaping circuit 60 according to a sixth embodiment of the present invention, which has the same structure as the constituent members shown in FIGS. 6A and 7A. The members have the same reference numerals. The analog signal waveform shaping circuit 60 of the eighth embodiment is different from the analog signal waveform shaping circuits 40 and 50 of the fourth and fifth embodiments of FIGS. 6 (a) and 7 (a). The attenuator 23 is provided between the switch SWP and the adder 27, and the changeover switch SWN and the adder 27 are provided.
An attenuator 24 is also provided between and, and the input signal is directly added to the adder 27. Except for this point, the circuit configuration of FIG. 8 (a) is shown in FIG.
Since the circuit configuration is the same as that shown in FIGS. 6A and 6A, the description thereof will be omitted.

The analog signal waveform shaping circuit 60 of the sixth embodiment is basically different from the above-described analog signal waveform shaping circuits 10 to 50 in the input signal waveform adjusting operation. Analog signal waveform shaping circuits 10 to 50 according to the above-described five embodiments.
Then, the input signal is separated into a positive signal and a negative signal, and the amplitude of one or both of them is adjusted so that the positive signal and the negative signal have the same amplitude. The signal of was added and the output waveform was made. However, the analog signal waveform shaping circuit 60 of the sixth embodiment is used.
In this case, since the input signal is directly added to the adder 27, only the correction amount for making the positive and negative amplitudes of the input signal the same is generated from the positive signal and the negative signal which are obtained by separating the input signal. This will be described with reference to FIG.

The input signal at point M in FIG. 8 (a) is shown in FIG.
As shown by the waveform in (b), the maximum amplitude Ap of the positive signal is
However, when the maximum amplitude An of the negative signal is larger than the maximum amplitude An of the negative signal, an output signal having a larger amplitude Ao than the positive or negative signal is produced in the sixth embodiment. Therefore, the changeover switch SW
When both P and SWN are connected to the positive and negative maximum amplitude detection circuit 13 side, the correction amount calculation circuit 14 is positive based on the maximum amplitude value of the positive and negative signals detected by the positive and negative maximum amplitude detection circuit 13. The difference Ao-Ap between the maximum amplitude Ap of the signal and the maximum amplitude Ao of the output signal, and the difference Ao-An between the maximum amplitude An of the negative signal and the maximum amplitude Ao of the output signal are calculated. Then, the correction amount calculation circuit 14 sets a gain such that the maximum amplitude Ap becomes the amplitude Ao-Ap in the attenuator 23,
A gain is set in the attenuator 24 so that the maximum amplitude An becomes the amplitude Ao-An.

As a result, when the changeover switches SWP and SWN are changed over to the attenuators 23 and 24, a signal of amplitude Ao-Ap shown by the waveform C appears at the N point and an amplitude shown by the waveform A at the O point. Ao-An signal appears. Therefore, in the adder 27, the amplitude of the positive component is Ap and the amplitude of the negative component is A.
n input signal, a positive signal of amplitude Ao-Ap, and a negative signal of amplitude Ao-An are input and added, and the output signal is a symmetrical signal of positive and negative amplitudes of amplitude Ao with both positive and negative amplitudes indicated by waveform no. Is obtained.

FIG. 9A shows the configuration of the analog signal waveform shaping circuit 70 according to the seventh embodiment of the present invention. An application example of the analog signal waveform shaping circuit 60 of FIG. 8A is shown. It shows the configuration of. Therefore, the same components as those in FIG. 8A are designated by the same reference numerals. The analog signal waveform shaping circuit 70 of the seventh embodiment is different from the analog signal waveform shaping circuit 60 of the embodiment of FIG.
The attenuator 23 is provided only on the positive signal path side, and a circuit having the inverting circuit 25 and a circuit not having the inverting circuit 25 between the attenuator 23 and the adder 27 are provided so as to be switchable by the changeover switch SW. That is, a changeover switch SWn is provided in front of the rectifier circuit 12 instead of the changeover switch SWN, and a negative signal is not input to the adder 27. Except for this point, the configuration of the circuit shown in FIG. 9A is the same as the configuration of the circuit shown in FIG.

In the analog signal waveform shaping circuit 70 of the seventh embodiment, the input signal is directly added to the adder 27 as in the analog signal waveform shaping circuit 60 of the sixth embodiment. The positive and negative amplitudes of the output signal are adjusted to the same value by adding the correction amount to the signal. On the other hand, in the analog signal waveform shaping circuit 60 of the sixth embodiment, the input signal is separated into a positive signal and a negative signal, the amplitudes of both are adjusted to create a correction amount, and this is added to the input signal. However, in the seventh embodiment, the correction amount is made only from the positive signal of the input signal, and the positive signal is output by increasing or decreasing the amplitude of the positive signal. The positive and negative amplitudes of the signal are adjusted to be the same. Figure 9
An explanation will be given using (b).

First, when the positive side component of the input signal is larger than the negative side component as indicated by the waveform P (solid line) at the point P shown in FIG. 9B, the correction amount calculation circuit 14 switches the changeover switch. SW is connected to the inverting circuit 25 side. The changeover switch SWP is connected to the positive and negative maximum amplitude detection circuit 13 side,
When the changeover switch SWn is turned on, the correction amount calculation circuit 14 calculates the amplitude difference Ad between the positive and negative signals based on the maximum amplitude value of the positive and negative signals detected by the positive and negative maximum amplitude detection circuit 13. Then, the correction amount calculation circuit 14 sets a gain in the attenuator 23 so that the maximum amplitude of the positive signal becomes Ad.

As a result, the changeover switch SWP is changed to the attenuator 2.
When the switch SWn is switched to the 3 side and the changeover switch SWn is turned off, a positive signal of the amplitude Ad shown by the waveform K appears at the point Q, and the amplitude Ad of the waveform Ad shown by the waveform Y appears at the point R on the output side of the inverting circuit 25. A negative signal appears. Therefore, the input signal and the negative signal of the amplitude Ad are input to the adder 27 and added, and the output signal is a positive / negative symmetrical signal having the same positive / negative amplitude indicated by the waveform "ma".

On the contrary, when the positive side component of the input signal is smaller than the negative side component as shown by the waveform o '(dotted line) at the point P shown in FIG. The changeover switch SW is connected to the attenuator 23 side. When the changeover switch SWP is connected to the positive and negative maximum amplitude detection circuit 13 side and the changeover switch SWn is turned on, the correction is performed based on the maximum amplitude value of the positive and negative signals detected by the positive and negative maximum amplitude detection circuit 13. The quantity calculation circuit 14 calculates the amplitude difference Ad between the positive and negative signals. Then, the correction amount calculation circuit 14 sets a gain in the attenuator 23 so that the maximum amplitude of the positive signal becomes Ad.

As a result, the changeover switch SWP is changed to the attenuator 2.
When the selector switch SWn is switched to the 3 side and the selector switch SWn is turned off, a positive signal of the amplitude Ad shown by the waveform K appears at the point Q, and this is directly input to the adder 27. Therefore,
The input signal and the positive signal of the amplitude Ad are input to the adder 27 and added, and a positive and negative symmetrical signal having the same positive and negative amplitudes indicated by the waveform m'is obtained as the output signal.

FIG. 10A shows the configuration of the analog signal waveform shaping circuit 80 according to the eighth embodiment of the present invention.
10 shows a configuration of a modified embodiment of the analog signal waveform shaping circuit 80 of FIG. 9 (a). Therefore, the same components as those of FIG. 9A are designated by the same reference numerals. The analog signal waveform shaping circuit 80 of the eighth embodiment is different from the analog signal waveform shaping circuit 70 of the embodiment of FIG. 9A in that the positive signal path and the negative signal path of FIG. 9A are different. The only difference is that the configuration is reversed. That is, in the eighth embodiment, the attenuator 24 is provided only on the negative signal path side, and the circuit having the inverting circuit 26 between the attenuator 24 and the adder 27 and the circuit not having the inverting circuit 26 are switched. A point that can be switched by a switch SW, and a changeover switch SWP
Instead of the rectifier circuit 12, a changeover switch SWp is provided in front of the rectifier circuit 12, and the input of a positive signal to the adder 27 is eliminated. Except for this point, the circuit configuration of FIG. 10 (a) is the same as the circuit configuration of FIG. 9 (a), and therefore the description thereof is omitted.

With the above configuration, the analog signal waveform shaping circuit 80 of the eighth embodiment makes the correction amount from only the negative signal of the input signal, and increases the amplitude of the negative signal.
Alternatively, the positive and negative amplitudes of the output signal are adjusted to be the same by decreasing the amplitude. This will be described with reference to FIG. First, when the negative side component of the input signal is larger than the positive side component as shown by the waveform (solid line) at point S shown in FIG. 10B, the correction amount calculation circuit 14 inverts the changeover switch SW. Connect to the circuit 26 side. The changeover switch SWN is connected to the positive and negative maximum amplitude detection circuit 13 side, and the changeover switch S
When Wp is on, the positive / negative maximum amplitude detection circuit 13
The correction amount calculation circuit 14 calculates the amplitude difference As between the positive and negative signals based on the maximum amplitude value of the positive and negative signals detected by. Then, the correction amount calculation circuit 14 sets a gain in the attenuator 24 such that the maximum amplitude of the negative signal becomes As.

As a result, the changeover switch SWN is changed to the attenuator 2.
When the changeover switch SWp is turned off, the negative signal of the amplitude As shown by the waveform K appears at the point T, and the negative signal of the amplitude As shown by the waveform U at the point U on the output side of the inverting circuit 26 appears. A positive signal appears. Therefore, the input signal and the positive signal of the amplitude As are input to the adder 27 and added, and a positive / negative symmetrical signal having the same positive / negative amplitude shown by the waveform D is obtained as the output signal.

On the contrary, the waveform case at point S shown in FIG.
As indicated by (dotted line), when the negative side component of the input signal is smaller than the positive side component, the correction amount calculation circuit 14 connects the changeover switch SW to the attenuator 24 side. Changeover switch SW
When N is connected to the positive and negative maximum amplitude detection circuit 13 side and the changeover switch SWp is turned on, the correction amount calculation is performed based on the maximum amplitude value of the positive and negative signals detected by the positive and negative maximum amplitude detection circuit 13. The circuit 14 has an amplitude difference A of positive and negative signals.
Calculate s. Then, the correction amount calculation circuit 14 uses the attenuator 2
The gain is set to 4 so that the maximum amplitude of the positive signal becomes As.

As a result, the changeover switch SWN is changed to the attenuator 2.
When the selector switch SWp is switched to the 4 side and the selector switch SWp is turned off, a positive signal of the amplitude As shown by the waveform F appears at the point T, and this signal is directly input to the adder 27. Therefore,
The input signal and the negative signal of the amplitude As are input to the adder 27 and added, and the output signal is a positive / negative symmetrical signal having the same positive / negative amplitude shown by the waveform d '.

FIG. 11 shows the configuration of an analog signal waveform shaping circuit 90 according to the ninth embodiment of the present invention.
FIG. 10 shows a configuration of a modified embodiment of the analog signal waveform shaping circuit 60 of FIG. Therefore, the same components as those in FIG. 8A are designated by the same reference numerals. The analog signal waveform shaping circuit 90 of the ninth embodiment is different from the analog signal waveform shaping circuit 60 of the embodiment of FIG. 8A in that it has an inverting circuit between the attenuators 23 and 24 and the adder 27. Two
5 and 26 are only provided. Except for this point, the configuration of the circuit of FIG. 11 is the same as the configuration of the circuit of FIG. 8 (a), so the description thereof will be omitted.

Next, the operation of the analog signal waveform shaping circuit 90 configured as described above will be described with reference to FIG. When the maximum amplitude AP of the positive signal is larger than the maximum amplitude AN of the negative signal, the input signal at the point V in FIG. 11 is positive and negative in the ninth embodiment, as shown by the waveform TE (solid line) in FIG. An output signal with a smaller amplitude AO than either signal is produced. Therefore, the changeover switches SWP, SW
When both N are connected to the positive and negative maximum amplitude detection circuit 13 side, the correction amount calculation circuit 14 determines the positive signal based on the maximum amplitude value of the positive and negative signals detected by the positive and negative maximum amplitude detection circuit 13. Maximum amplitude AP and maximum output signal amplitude A
The difference AP-AO of O and the difference AN-AO of the maximum amplitude AN of the negative signal and the maximum amplitude AO of the output signal are calculated. Then, the correction amount calculation circuit 14 sets a gain in the attenuator 23 such that the maximum amplitude AP becomes the amplitude AP-AO, and the attenuator 2
In 4, the gain is set so that the maximum amplitude AN becomes the amplitude AN-AO.

As a result, when the changeover switches SWP, SWN are switched to the attenuators 23, 24 side, a positive signal of the amplitude AP-AO shown by the waveform A appears at the point W and the waveform support at the point X. A negative signal of the indicated amplitude AP-AO appears. Similarly, a negative signal of amplitude AN-AO indicated by the waveform K appears at the point Y, and a positive signal of amplitude AN-AO indicated by the waveform U appears at the point Z. Therefore, the amplitude of the positive component is A in the adder 27.
An input signal whose amplitude of the negative component is P and which is AN, amplitude AP-AO
Negative signal and a positive signal of amplitude AN-AO are input and added, and a positive and negative symmetrical signal of amplitude AO is obtained in the output signal with both positive and negative amplitudes shown by the waveform waveform.

[0047]

As described above, according to the present invention, by dividing the positive and negative components of the analog signal and adjusting the gains independently of each other, it is possible to obtain an output waveform in which the positive and negative amplitudes are symmetrical. There is. As a result, the present invention can be applied to, for example, a circuit for correcting the positive / negative asymmetric component of the reproduced waveform of the MR head in the magnetic disk device, and has the effect of simplifying the circuit configuration and reducing the cost.

[Brief description of drawings]

FIG. 1 is a principle configuration diagram showing a configuration of an analog signal waveform shaping circuit of the present invention.

FIG. 2 shows a first embodiment of the present invention (a)
Is a block circuit diagram showing the configuration of an analog signal waveform shaping circuit, and (b) is a waveform diagram showing the operation of the main part of (a).

3A and 3B show one embodiment of the configuration of the rectifier circuit of FIG. 1, where FIG. 3A is a block circuit diagram of the rectifier circuit, and FIG. 3B is a waveform diagram showing the operation of the main part of FIG. .

FIG. 4 shows a second embodiment of the present invention, (a)
Is a block circuit diagram showing the configuration of an analog signal waveform shaping circuit, and (b) is a waveform diagram showing the operation of the main part of (a).

FIG. 5 shows a third embodiment of the present invention, (a)
Is a block circuit diagram showing the configuration of an analog signal waveform shaping circuit, and (b) is a waveform diagram showing the operation of the main part of (a).

FIG. 6 shows a fourth embodiment of the present invention, (a)
Is a block circuit diagram showing the configuration of an analog signal waveform shaping circuit, and (b) is a waveform diagram showing the operation of the main part of (a).

FIG. 7 shows a fifth embodiment of the present invention, (a)
Is a block circuit diagram showing the configuration of an analog signal waveform shaping circuit, and (b) is a waveform diagram showing the operation of the main part of (a).

FIG. 8 shows a sixth embodiment of the present invention, (a)
Is a block circuit diagram showing the configuration of an analog signal waveform shaping circuit, and (b) is a waveform diagram showing the operation of the main part of (a).

FIG. 9 shows a seventh embodiment of the present invention, (a)
Is a block circuit diagram showing the configuration of an analog signal waveform shaping circuit, and (b) is a waveform diagram showing the operation of the main part of (a).

FIG. 10 shows an eighth embodiment of the present invention,
(a) is a block circuit diagram showing the configuration of an analog signal waveform shaping circuit, and (b) is a waveform diagram showing the operation of the main part of (a).

FIG. 11 is a block circuit diagram showing a configuration of an analog signal waveform shaping circuit according to a ninth embodiment of the present invention.

12 is a waveform chart showing the operation of the main part of FIG.

[Explanation of symbols]

 1 ... Positive / negative maximum amplitude detection means 2 ... Correction amount calculation means 3 ... Amplitude correction means 5 ... Training signal writing circuit 6 ... Inductive head 7 ... Magnetic disk 8 ... MR head 9 ... Head IC 10 ... Of the first embodiment Analog signal waveform shaping circuit 11, 12 ... Rectifier circuit 13 ... Positive / negative maximum amplitude detection circuit 14 ... Correction amount calculation circuit 20 ... Analog signal waveform shaping circuit 21, 22 ... Amplifier / attenuator 23, 24 ... Attenuator 25, 26 ... Inversion circuit 27 ... Adder 30 ... Analog signal waveform shaping circuit of the second embodiment 31 ... Comparator 32, 33 ... Selector 40 ... Analog signal waveform shaping circuit of the fourth embodiment 50 ... Analog signal waveform shaping circuit of the fifth embodiment 60 ... Analog signal waveform shaping circuit of the sixth embodiment 70 ... Analog signal waveform of the seventh embodiment Shape circuit 80 ... eighth embodiment of an analog signal of the waveform shaping circuit 90 ... ninth embodiment analog signals of the waveform shaping circuit SWN of, SWP, SWn, SWp ... changeover switch

Claims (5)

[Claims] 1. A circuit for shaping a waveform so that positive and negative amplitudes of an alternating-current analog signal having different positive and negative amplitudes with respect to a reference 0 level are the same, and a positive and negative signal with respect to a reference level of an input analog signal is provided. Positive and negative maximum amplitude value detecting means (1) for detecting the maximum amplitude value, and a correction for making the amplitude of the analog signal equal to the reference level from the detected value of the positive and negative maximum amplitude value detecting means (1). Correction amount calculation means (2) for calculating the amount, and amplitude correction means for correcting the amplitude of the analog signal according to the correction amount calculated by the correction amount calculation means (2)
(3) An analog signal waveform shaping circuit comprising: 2. A signal branching means for dividing the analog signal into a positive signal having a level on the positive side of the 0 level and a negative signal having a level on the negative side, the amplitude correcting means (3) comprising: 3. A correction means for performing amplification correction or attenuation correction on at least one of the branched positive signal and negative signal, and a signal synthesizing means for synthesizing the corrected signals. A waveform shaping circuit for analog signals according to. 3. The amplitude correction means (3) is a signal extraction means for extracting a positive signal having a level on the positive side of the 0 level or a negative signal having a level on the negative side from the analog signal, and extracted. The correction means for performing amplification correction or attenuation correction on a positive signal or a negative signal, and a signal synthesizing means for synthesizing the corrected signal with the original signal. Waveform shaping circuit for analog signals. 4. The amplitude correction means (3) has three types of analog signals, a positive signal having a level on the positive side of the 0 level, a negative signal having a level on the negative side, and a signal as it is. Signal branching means for dividing into signals, correction means for performing amplification correction or attenuation correction on at least one of the branched positive signal and negative signal, and a signal for combining the corrected signal with the original analog signal The analog signal waveform shaping circuit according to claim 1, further comprising a synthesizing unit. 5. The waveform shaping of the analog signal according to claim 1, wherein the analog signal is a signal read by an MR head from a magnetic disk of a magnetic disk device. circuit.