JPS5946042B2 - Magnetic information reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic information reproducing apparatus using a reproducing head made of a magnetoresistive element.

FIG. 1 shows an example of a magnetic information reproducing apparatus using a conventional magnetoresistive element.

When magnetic information recorded on the magnetic tape 1 is retrieved via the magnetoresistive element 2, the magnetic field that the magnetoresistive element 2 receives from the magnetic tape 1 is defined as: H) The electric resistance of the magnetoresistive element 2 due to the magnetic field is defined as "R". If the current flowing through the magnetoresistive element 2 by the current circuit 3 is I, the voltage E generated across the magnetoresistive element 2 under an appropriate bias magnetic field is EocJR-I-
They have an H relationship. If you want to increase the voltage E across the magnetoresistive element 2 and take it out as an output signal to the reproduction amplifier 4, either 10ΔR or H must be increased, but H is recorded on the magnetic tape 1. It is determined by magnetic information, and ΔR is determined by the characteristics of the magnetoresistive element 2. Therefore, the only way to obtain a large output signal is to increase the current I flowing through the magnetoresistive element 2.
When I is increased, the power consumption of the magnetoresistive element 2 increases, which eventually leads to the destruction of the magnetoresistive element 2. In particular, since the magnetoresistive element has a thin film structure, the current that can be passed through the magnetoresistive element is severely limited, which is an obstacle to extracting a large output signal. In view of these circumstances, it is an object of the present invention to provide a magnetic information reproducing device that uses a magnetoresistive element and can significantly increase the output signal.

The present invention will be explained below with reference to an embodiment shown in FIG.

A magnetoresistive element 6 is placed opposite to the magnetic tape 5. A magnetic field H as information is generated on the surface of the magnetic tape 5, and the magnetic field H changes as the magnetic tape 5 moves in the direction of arrow A. When the change in the magnetic field H is expressed with time T as the horizontal axis, it becomes as shown in FIG. 3a. A constant current pulse circuit 7 is connected to the magnetoresistive element 6, and a pulse current having a constant pulse height is intermittently passed through the magnetoresistive element 6. The waveform of this pulse current is shown in FIG. 3b. Here, assuming that the pulse rest i period is a pulse in which the pulse current becomes zero (RZ pulse: return-to-zero pulse), the voltage E across the magnetoresistive element 6
s becomes Es=ΔR−H−Ip. However, Ip is the peak value of the pulse current, Es is the peak value of the pulse voltage,
This Es becomes the output signal. The output signal Es becomes a pulse train having different heights as shown in FIG. 3c. After detecting this pulse train with a detector 8 such as a reproducing amplifier, the sample
By sampling and holding in the hold circuit 9, a waveform signal as shown in FIG. 3d is obtained. By passing this signal through the filter circuit 10, an output as shown in FIG. 3e can be obtained. Note that sampling in the sample/hold circuit 9 must be performed in synchronization with the constant current pulse circuit 7 when the current 1 flowing through the magnetoresistive element 6 reaches its peak. In addition, the shorter the period t of the pulse current 1 flowing through the magnetoresistive element 6, the more accurate reproduction is possible, but there is a limit in terms of the average current value.The pulse frequency derived from the period t of the pulse current 1 is sampled. According to the theorem, at least twice the signal to be reproduced is required.The power consumption of the magnetoresistive element in such a device is 12·ΔR, which is proportional to the square of the average current 1.

Therefore, as in the present invention, the pulse current is passed through the magnetoresistive element 6.
When the current is passed through the current, the average current 1 becomes small and the power consumption becomes very small. Therefore, if the same average current as in the conventional device is used, the peak value of the pulse current can be made sufficiently large. Therefore, the output voltage is extremely large, more than 10 times that of conventional devices. Furthermore, when obtaining the same output voltage as the conventional one, the power consumption in the magnetoresistive element 6 can be reduced, and the temperature rise of the magnetoresistive element 6 can be kept low. Although an example has been shown in which the magnetic tape 5 is used as the medium, the present invention is not limited to this, and other magnetic recording media such as a magnetic card or a magnetic drum may be used.

Further, the effect of the present invention can be obtained even if a pulse current that does not return to zero during the rest period is used as the pulse current flowing through the magnetoresistive element.
In other words, while a minute current is flowing through the magnetoresistive element, a pulse current may be superimposed thereon. In short, the present invention can be implemented with various modifications without departing from the gist thereof. As explained above, the present invention uses a pulse current as the current flowing through the magnetoresistive element in a magnetic information reproducing device using a magnetoresistive element, so that the magnetic It is possible to provide an information reproducing device.

[Brief explanation of the drawing]

Fig. 1 shows an example of a conventional magnetic information reproducing device, Fig. 2 shows an example of a conventional magnetic information reproducing device;
The figure is a diagram showing the configuration of an embodiment of the present invention, and Figures 3a to 3e are waveform diagrams showing the operation of the same embodiment, where a is a waveform diagram of the magnetic field H due to magnetic information, and b is a waveform diagram of the magnetic field H flowing through the magnetoresistive element. Pulse current P
c is a waveform diagram of the pulse voltage Es generated across the magnetoresistive element, d is a waveform diagram of the sampled and held voltage, and e is a waveform diagram of the reproduced output voltage passed through the filter 1. 1, 5... Magnetic tape, 2, 6... Magnetoresistive element, 3... Constant current circuit, 4...
・Reproduction amplifier, 7... Constant current pulse circuit, 8.
...Detector, 9...Sample/hold circuit, 10...Filter circuit, 11...
...Integrator circuit.

Claims (1)

[Claims] 1. A magnetic recording medium, a reproducing head consisting of a magnetoresistive element placed opposite to the recording surface of the recording medium, a circuit that repeatedly applies a pulse signal to this head, and a magnetic recording medium generated at both ends of the magnetoresistive element when the pulse signal is applied. 1. A reproducing device for magnetic information, comprising: means for detecting a signal; and a circuit for sampling and holding the signal detected by the detecting means to extract magnetic information.