JPH0441451Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a read/write circuit for a magnetic storage device, and more particularly to a read/write circuit for a magnetic storage device that performs reading and writing using the same magnetic head.

Flotspy disk (flexible disk)
BACKGROUND OF THE INVENTION In devices and other magnetic storage devices, reading and writing are often performed using the same magnetic head. On the other hand, although this method is advantageous in terms of reducing head weight and simplifying the structure, since the read circuit and write circuit are connected in parallel to the magnetic head, the S
In addition to the drawback that the N ratio is not very good, there are other problems such as oscillation, and countermeasures against this problem have been one of the difficulties in device design.

An object of the present invention is to provide a read/write circuit for a magnetic storage device that can improve the above-mentioned drawbacks and easily obtain a high S/N ratio.

Therefore, in the present invention, in a read/write circuit of a magnetic storage device that performs reading and writing using the same magnetic head, the signal to the magnetic head for writing is transmitted via a FET switch circuit that is opened and closed by a write gate signal. The purpose of the present invention is to achieve the above object.

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

In FIG. 1, 2 indicates a magnetic head for reading and writing. During reading, the output of the magnetic head 2 is first amplified to a predetermined level by a discrete type preamplifier 4 (see Figure 2 for details), then greatly amplified by a video amplifier 5, and then passed through a low-pass filter. 6. After passing through a differentiator 7 and a zero cross detector 8, the waveform is shaped by a waveform shaping circuit 9 and output as read data. In the readout circuit 1 thus constructed, the midpoint 2A of the coil of the magnetic head 2 is grounded via a bypass capacitor 3. Further, a write power switching transistor 10 that functions during writing, which will be described later, is connected to this midpoint 2A, and is configured to be controlled by a write gate signal.

The input/output terminals of the magnetic head 2 further include
Write circuit 5 via FET switch circuit 30
1 is connected. The FET switch circuit 30 is
It is composed mainly of FETs 20 and 21, and has a function of separating the write circuit during the aforementioned read operation to improve the S/N ratio during the read operation. Furthermore, this FET switch circuit 3
0, 22 and 23 are resistors connected between the gate and source, 24 and 25 are diodes for blocking forward current, 26 is a FET intermittent transistor, and 2
7 is its collector resistor, 28 is a resistor connected between the emitter and base, and 29 is a base resistor.
Further, in the write circuit 51, 10 is a write power switching transistor, 11 is a resistor connected between the emitter and the base, 12 is a base resistor, and 13 is a resistor connected between the emitter and the base.
is a 1/2 frequency divider composed of D flip-flops,
14, 15 and 16 are buffers, 17 and 18 are write drivers, and 19 is a write driver intermittent transistor.

The embodiment of FIG. 1 having such a configuration operates as follows.

First, during writing, the write gate signal (active low) is applied to the write power switching transistor 1.
0, preamplifier 4, FET intermittent transistor 26,
The signal is applied to write driver intermittent transistor 19 and waveform shaper 9, respectively. As a result, the base and emitter of the transistors in the preamplifier 4 are shorted and the amplification operation is stopped (see Figure 2), and the waveform shaper 9 is also connected to the enable terminal of one of the ICs in the circuit. When it goes low level, its operation is stopped, thereby preventing the write signal from flowing into the read circuit 1. Also,
When the write power switching transistor 10 becomes conductive, a power supply voltage +V is applied to the midpoint 2A of the coil of the magnetic head 2. Furthermore, the FET intermittent transistor 26 becomes conductive and the transistor 26 becomes conductive.
The collector side of the transistor becomes a positive potential close to approximately +Vc, so that the diodes 24 and 25 are cut off and the FETs 20 and 21 are made conductive. At the same time, the write driver intermittent transistor 19 also becomes conductive.
Therefore, the write circuit 51 becomes in a writable state.

When write data is supplied in such a state, this data is frequency-divided by 1/2 by the D flip-flop 13 and becomes an output Q and a signal. This signal is supplied to write drivers 17 and 18 via buffers 14 and 15. The write drivers 17 and 18 are turned on and off in accordance with this Q and the signal, thereby causing a writing excitation current to flow through the coil of the magnetic head 2.

On the other hand, during reading, as a result of the write gate signal being cut off, each of the circuits receiving this signal is placed in the opposite state. That is, the preamplifier 4 and the waveform shaper 9 are activated, but the write power switching transistor 10, the FETs 20 and 21, and the write driver intermittent transistor 19 are disconnected, so that only the readout circuit 1 is activated.

In such a state, a minute output signal generated at both ends of the coil of the magnetic head 2 as a floppy disk or the like rotates is first amplified by a preamplifier 4, then further amplified by a video amplifier 5, and then supplied to a low-pass filter 6. The extra high-frequency components are removed here. Next, this low pass filter 6
The signal that has passed is differentiated by a differentiator 7, and its peak point is relayed to the zero-crossing point of the differentiated waveform. This zero cross point is detected by the zero cross detector 8, and the output pulse thereof is shaped by the waveform shaper 9 into a pulse having a predetermined width and a predetermined wave height, and is sent out as read data.

As mentioned above, the conventional read/write circuit has a poor S/N ratio during this read operation, but in this embodiment, the FET switch circuit 30
Since the method of completely disconnecting the write circuit 51 during the read operation is adopted, various noises such as leakage current of transistors, which conventionally were mixed in from the write circuit 51 during the read operation, are almost eliminated. completely removed, which significantly improved the S/N ratio. When the inventors actually observed the output waveform of the video amplifier 5 using a synchroscope, they found that in the conventional circuit,
The data signal, set at 62.5KHz, was almost hidden in the noise, making it difficult to identify. However, in the case of this example, even when the above-mentioned bypass capacitor was not used, the data signal at 62.5 KHz appeared extremely clearly, and a remarkable difference from the conventional circuit was observed.

In the above embodiment, the preamplifier 4 is of a discrete type in order to further improve the S/N ratio, but the present invention does not necessarily limit the preamplifier 4 to a discrete type. .

As described above, according to the present invention, in a read/write circuit of a magnetic storage device that performs reading and writing using the same magnetic head, a signal to the magnetic head for writing is transmitted through a FET switch that is opened and closed by a write gate signal. Since the configuration is such that the signal is supplied through the circuit, the write circuit can be completely disconnected during reading, which greatly improves the S/N ratio and eliminates oscillation phenomena compared to conventional systems. Thereby, it is possible to provide a practical read/write circuit for a magnetic storage device that can stabilize its operation.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention.
FIG. 2 is a circuit diagram showing details of the preamplifier in FIG. 1. 2...Magnetic head, 30...FET switch circuit, 51...Write circuit.

Claims (1)

[Scope of utility model registration request] In a read/write circuit of a magnetic storage device in which reading and writing are performed using the same magnetic head, a signal to the magnetic head for writing is supplied via a FET switch circuit that is opened and closed by a write gate signal. A read/write circuit for a magnetic storage device characterized by: