JPH04129002A - Detection of waveform distortion - Google Patents

Abstract

PURPOSE:To quickly and easily detect even a minute wavaeform distortion by generating a distortion alarm signal at the time when the peak hold value of a peak holding circuit exceeds a threshold. CONSTITUTION:Output + or -Vpk of a peak holding circuit 8 are inputted to a differential amplifier 12 and are amplified to a prescribed level. When the waveform is normal, the output of the differential amplifier 13 is 0V because the output level on the positive side and that on the negative side are equal to each other. If the waveform is distorted, a voltage proportional to the difference in output level between the positive side and the negative side is outputted. The output of the differential amplifier 13 is inputted to a comparator 14 and is compared with distortion detection threshold Vs1 and Vs2 by the comparator 14, and an alarm signal AL is generated in a circuit in the succeeding stage when the peak hold output exceeds the distortion detection threshold +Vs1 or -Vs2. Thus, a minute waveform distortion is quickly and easily detected.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to a waveform distortion detection method for a small signal amplifier circuit that equalizes and amplifies the output of a magnetic head, and an object of the present invention is to provide a waveform distortion detection method that can quickly and easily detect minute waveform distortions. Yes, in the waveform distortion detection method of the small signal amplification circuit that equalizes and amplifies the magnetic head output,
At the time of diagnosis, a test data generation circuit generates input test data by switching with the magnetic head output, a peak hold circuit holds the peak value of the output of the small signal amplification circuit, and the output of the peak hold circuit is set to a predetermined value. The test data is inputted at the time of diagnosis, and when the peak hold value of the peak hold circuit obtained through the small signal amplification circuit exceeds the threshold value, distortion is detected. Configure alarms to occur.

[Industrial application field]

The present invention relates to a waveform distortion detection method for detecting waveform distortion of a small signal amplification circuit that equalizes and amplifies the output of a magnetic head and diagnosing a defective location.

Not limited to small signal amplification circuits that equalize and amplify the output of magnetic heads, but with the miniaturization and lower power consumption of circuits in general, consideration is being given to IC design that eliminates unnecessary functions as much as possible, as well as simplification of the IC manufacturing process. has been done.

On the other hand, an important point in simplifying the manufacturing process is how to keep the process defect rate low. - An example is diagnosing waveform distortion in a small signal amplification circuit during the manufacturing process.
In particular, it is necessary to detect minute waveform distortions in the circuit itself with high precision and quickly.

[Conventional technology]

FIG. 4 is an example of a conventional small signal amplification circuit.

As the magnetic head 1, a magnetic head (hereinafter referred to as an MR head) using a magnetoresistive element is widely used. A magnetoresistive element is an element that utilizes the property of a semiconductor that its resistance value changes with changes in external magnetic flux.

In FIG. 4, the small signal amplifier circuit includes a preamplifier (preamplifier) 2 that receives the output from the MR head 1, a differential equalizer circuit 3, an amplifier circuit 4, a voltage control amplifier circuit 5, an equalizer correction circuit 6, and an amplitude comparison circuit. It is composed of a circuit 7.

A read clock R-CLK and read data RDA are obtained through this small signal amplification circuit, a peak hold circuit 8, a data separator 9, and a VFO circuit 10.

11 is a T-port NE/VDIO detection circuit. This circuit creates a specific data pattern from the read data obtained above.
For example, it detects a data pattern indicating the beginning of a data block written on a magnetic tape.

Reference numeral 12 denotes an LWR data creation circuit, which will be described later, which switches the magnetic head output during circuit diagnosis to generate test data and sends it to the small signal amplification circuit.

In this case, the LWR method has been conventionally used as a method for diagnosing waveform distortion in a small signal amplification circuit. LWR(
The Loop Write to Read (Loop Write to Read) method is a method for diagnosing the circuit without using the output of the magnetic head 1.
Test data from the LWR data generation circuit 12 is input to the preamplifier 2 instead of the output of the head, and distortion of the small signal amplification circuit is detected using this test data.

[Problem to be solved by the invention]

However, there are minute distortions that cannot be detected using conventional methods.

This will be explained below. As shown in Figure 4, M
The R head 1 is shut off and the test data from the LWR data creation circuit 12 is input to the preamplifier 2. The test data from the LWR circuit is, for example, a sine wave. The output of the amplitude comparator circuit 7 in FIG. 4 is a sine waveform in an ideal case without distortion, as shown by the solid line in FIG. 2, and should be a horizontally/vertically symmetrical waveform.

However, in the IC manufacturing process, for example, the waveform may be distorted as shown by the dotted line due to variations in the manufacturing loft, such as due to a drift in the operating point due to a change in the current amplification factor hfe of the transistor.

On the other hand, it is extremely difficult to remove all of these when testing a single IC, and a certain amount of defects will eventually be mixed in.

Although such defects do not directly pose a major problem,
This may cause an increase in data reading errors.
It may take a great deal of effort to resolve this obstacle.

An object of the present invention is to provide a waveform distortion detection method that can quickly and easily detect minute waveform distortions in a small signal amplification circuit that equalizes and amplifies the output of a magnetic head.

[Means to solve the problem]

The present invention is a waveform distortion detection method for a small signal amplifier circuit that equalizes and amplifies the output of a magnetic head, and includes a test data generation circuit 12 that generates test data to be input by switching with the output of the magnetic head during diagnosis; A peak hold circuit 8 that holds the peak value of the output of the small signal amplification circuit, and a comparison circuit 14 that compares the output of the peak hold circuit with a predetermined threshold, inputs the test data at the time of diagnosis, The present invention is characterized in that a distortion alarm is generated when the peak hold value of the peak hold circuit obtained through the small signal amplification circuit exceeds the threshold.

[For production]

In diagnosing waveform distortion of a small signal amplifier circuit, a peak hold signal is generated from the signal amplified by the small signal amplifier circuit, this is input to a differential amplifier, and after amplification, this peak hold signal is output to a comparator. It compares with a threshold value and generates an alarm signal if it exceeds it.

〔Example〕

FIG. 1 is a configuration diagram of an embodiment of the present invention. A differential amplifier 13 that differentially amplifies the output of the peak hold circuit 8 and a comparison circuit 14 that compares the peak hold signal that is the output of the peak hold circuit with a threshold are added to the circuit of FIG. 4 as shown. do.

FIG. 2 is an explanatory diagram comparing the normal waveform and the distorted waveform output from the small signal amplification circuit as described above.

FIG. 3 is an explanatory diagram of the waveform detection 8-distortion method of the present invention. To generate an error detection signal for each track.

First, the LWR data generation circuit that generates test data is operated, the test data is input to the small signal amplifier circuit, and the small signal amplifier circuit outputs an amplified sine wave. In this case, it is assumed that if the small signal amplification circuit is completely normal and there is no distortion, a sine wave that is horizontally/vertically symmetrical as shown by the solid line in FIG. 2 will be obtained.

The amplified waveform is input to the peak hold circuit 8.

The peak hold circuit 8 is a circuit that follows the level of the input signal and holds its peak value, and the hold value decreases as shown in the figure until the next peak pulse is generated.

In FIG. 3, the solid lines are the positive side and negative side waveforms input to the peak hold circuit 8, and if the input waveform is distorted, a difference occurs between the positive side and negative side input levels. The dotted line is the output waveform of the peak hold circuit 8, which changes in response to changes in the peak value of the distortion waveform. - The dashed line is the distortion detection threshold.

As shown in FIG. 1, the output of the peak hold circuit 8 ±V
pk is input to the differential amplifier 14 and amplified to a predetermined level. If the waveform is normal, the positive side and negative side output levels are the same, so the output of the differential amplifier 14 is OV. However, when waveform distortion occurs, a voltage output proportional to the difference between the output levels on the positive side and the negative side is obtained.

Next, the output of the differential amplifier 14 is input to the comparator 12. In the comparator 12, the third T! It is compared with distortion detection thresholds VSI and VS2 shown by dashed lines at A. Peak hold output is distortion detection threshold +Vsl or -Vs
When the value exceeds 2, an alarm signal AL is generated in a subsequent circuit.

In the above explanation, the output of the peak hold circuit 8 is differentially amplified by the differential amplifier 1.3 and then compared with the threshold in the comparator circuit 14, but the positive and negative outputs of the peak hold circuit 8 are Each is amplified to an appropriate level and sent to the comparison circuit 14.
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〔Effect of the invention〕

As described above, according to the present invention, minute waveform distortion in a small signal amplification circuit that equalizes and amplifies the magnetic head output can be quickly and easily detected.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of an embodiment of the present invention, Fig. 2 is an explanatory diagram comparing normal waveforms and distorted waveforms, Fig. 3 is an explanatory diagram of waveform distortion detection of the present invention, and Fig. 4 is a conventional configuration diagram. It is. (Explanation of symbols) 1...Magnetic head, 2...Preamplifier, 3
...Differential equalizer, 4...Amplification circuit, 5...
Power supply control amplifier circuit, 6... Equalizer correction circuit, 7... Amplitude comparison circuit, 8... Peak hold circuit, 9... Data separator, 1 (lh/V FO circuit, 11-T port NE /V
OID12...LWR data creation circuit, 13...Differential amplifier circuit, 14...Comparison circuit. circuit,

Claims (1)

[Claims] 1. In a waveform distortion detection method for a small signal amplifier circuit that equalizes and amplifies the output of a magnetic head, the test data generation circuit ( 12), a peak hold circuit (8) that holds the peak value of the output of the small signal amplification circuit, and a comparison circuit (14) that compares the output of the peak hold circuit with a predetermined threshold; A distortion alarm signal (AL) is generated when the peak hold value of the peak hold circuit obtained by inputting the test data through the small signal amplification circuit exceeds the threshold value. A waveform distortion detection method that uses 2. The waveform distortion detection method according to claim 1, wherein the magnetic head (1) is a magnetoresistive element. 3. The test data generation circuit (12) is LWR (Loop
The waveform distortion detection method according to claim 1, which is a write-to-read method.