Dynamic magnetic information storage or retrieval – General recording or reproducing – Specifics of the amplifier
Reexamination Certificate
1999-05-17
2001-11-27
Neal, Regina Y. (Department: 2753)
Dynamic magnetic information storage or retrieval
General recording or reproducing
Specifics of the amplifier
C360S046000
Reexamination Certificate
active
06324028
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a recording apparatus for recording an information signal on a magnetic record carrier, the apparatus comprising:
an input terminal for receiving the information signal,
a write driver circuit and
a magnetic write head, the write driver circuit comprising
a first voltage driver having an input coupled to the input terminal of the apparatus, and an output coupled to a first terminal of the magnetic write head,
a second voltage driver having an input coupled to the input terminal of the apparatus and an output coupled to the second terminal of the write head, as well as to a write driver circuit for use in the recording apparatus.
Write drivers of the voltage drive type are well known in the art. Reference is made in this respect to U.S. Pat. No. 4,853,800 (D1 in the list of related documents that can be found at the end of this description) and DE-A 2,735,498 (D2).
There is a strong pressure, especially on hard-disk drive manufacturers, to increase bit density and to shorten access times. The current rate of increase in bit density (60 % per annum) is being sustained by a variety of technical improvements with a resulting increase in data rates of 40 % per year. In order to sustain this increase in data rates, the high frequency performance of the media, heads and electronics, in particular the write driver, have to increase at the same rate.
Conventional write driver techniques, based on current driving, see D3, current steering, see D4, have severe speed limitations. These limitations result not only from poor high-frequency performance inside the driver, but also from limitations imposed by the head-amplifier combination. In addition to the poor high-frequency performance of thin-film write heads, these shortcomings have become a major limitation in the write process for magnetic recording.
SUMMARY OF THE INVENTION
It is an object of the invention to further improve the recording characteristics of the recording apparatus. The recording apparatus in accordance with the invention is characterized in that the first voltage driver circuit comprises an output circuit of a series arrangement of an npn transistor and an impedance, coupled between a point of a first constant potential and the output of the first voltage driver circuit,
that the second voltage driver circuit comprises an output circuit of a series arrangement of an npn transistor and an impedance, coupled between said point of a first constant potential and the output of the second voltage driver circuit, the apparatus further comprising
a first current driver having an input coupled to the input terminal and an output coupled to said first terminal of the write head, and
a second current driver having an input coupled to the input terminal and an output coupled to said second terminal of the write head. The invention is based on the recognition to combine voltage drive and current drive techniques in order to obtain an improved recording apparatus.
A voltage driver is proposed for the reason that it does not only has a superior internal high-frequency performance, but is also less sensitive to the performance limitations resulting from head-amplifier combinations. Further, by adding a current driver, preferably comprising at least one transistor of the npn type, coupled between its output and the point of a second constant potential, which is the negative supply voltage, an improved behavior can be obtained. Both the current driver as well as the voltage driver have been realized by npn transistors. npn transistors are much faster in their characteristics, so that replacing the pnp transistor normally present in a current driver circuit by a voltage driver having an npn transistor in its output circuit speeds up the circuit significantly.
The write driver proposed herein has a major advantage in that it can be integrated in a chip area much smaller than that used for previous current drivers. The reduced chip area comes as a result of an improved architecture.
REFERENCES:
patent: 4853800 (1989-08-01), Schulz
patent: 5357379 (1994-10-01), Gower
patent: 5986832 (1999-11-01), Barnett
patent: 6008719 (1999-12-01), Jolivet
patent: 2735498A1 (1979-02-01), None
“150 Mb/s Write Amplifier for Hard Disk Drives with Near Rail-to-Rail Voltage Swing”, H. Veenstra et al., 1995.
“A Resonant Switching Write Driver for Magnetic Recording”, Richard Reay et al., IEEE Journal of Solid-State Circuits, vol. 32, No. 2, Feb. 1997.
De Jong Gerben W.
Le Luan
Pieraerts Eric
Ramalho Joao N. V. L.
Voorman Johannes O.
Franzblau Bernard
Neal Regina Y.
U.S. Philips Corporation
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