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Patent Issued for High Impedance Low Noise Cross-Coupled Amplifier for Use in as a Preamplifier in a Magnetic Data Storage System

August 12, 2014



By a News Reporter-Staff News Editor at Information Technology Newsweekly -- A patent by the inventors Straub, Michael (Longmont, CO); Krebs, Andrew P. (Eagan, MN), filed on December 27, 2013, was published online on July 29, 2014, according to news reporting originating from Alexandria, Virginia, by VerticalNews correspondents.

Patent number 8792198 is assigned to LSI Corporation (San Jose, CA).

The following quote was obtained by the news editors from the background information supplied by the inventors: "The present invention relates to magnetic data storage systems generally and, more specifically, to low noise balanced preamplifiers useful for read and control channels in magnetic storage systems.

"A popular method of magnetic data storage utilizes magnetoresistive (MR) heads to store and recover data on a magnetic data storage medium such as a magnetic disk. An MR head employs an MR element that changes in resistivity with changing magnetic flux from data patterns on an adjacent magnetic disk surface. A bias current having a constant value is passed through the MR element, and the change in resistivity is measured by sensing the change in voltage across the MR head.

"Preamplifier circuits that sense signals directly from a MR head commonly include differential inputs and differential outputs. A preamplifier is typically embodied in an integrated circuit, possibly with other preamplifiers and other circuitry such as write drivers, and is collocated with, or is positioned very near, the MR head. While there are a wide variety of balanced amplifier circuit topologies, most include an input stage driving two load resistors and symmetrical transistors for splitting current between the load resistors to generate an amplified output signal. Usually, the output signal is a differential voltage taken as the difference in the voltage drops across the load resistors; in this manner, large variations in output voltages may be achieved with extremely small input voltage differentials.

"New magnetic storage technologies require sensing how high the MR head is above the rotating magnetic disk (referred to herein as fly-height control) in addition to reading data from the disk. To do so, multiple control systems are connected to a fly-height sensing head, co-located with the MR head, to read how high the head is from the magnetic disk media during the reading of information therefrom. Previously the frequency bands of two of the control systems, referred to as DC sense and thermal asperity (TA) sense, did not overlap so interaction between the DC and TA sense systems was typically not a factor. However, new magnetic storage systems utilize overlapping frequency bands for fly-height control. Existing preamplifier designs have too low an input impedance to permit connecting the two sense paths to the same sense head because the frequency response of the preamplifier is not sufficiently flat over the bandwidth of the signals being amplified by the preamplifier. Thus, a new preamplifier design is desired to provide a substantially flat frequency response over the overlapping frequency bands of the DC and TA sense systems."

In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventors' summary information for this patent: "This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

"In one embodiment of the invention, a balanced amplifier circuit for amplifying an input signal and for providing an output signal is disclosed. The balanced amplifier comprises first and second input signal nodes, first and second amplifier circuits, and first and second coupling circuits. The first amplifier circuit has an input transistor and a cross-coupling transistor, the input transistor having a control terminal connected to the first input signal node, a first output terminal coupled to a first output terminal of the cross-coupling transistor, and a second output terminal coupled to a first power supply node. The second amplifier circuit has an input transistor and a cross-coupling transistor, the input transistor having a control terminal connected to the first input signal node, a first output terminal coupled to a first output terminal of the cross-coupling transistor, and a second output terminal coupled to the first voltage node. The first coupling circuit including a capacitor and a coupling transistor, the first coupling circuit being connected such that a control terminal of the coupling transistor is connected to the first input signal node and the capacitor is connected between a first output terminal of the coupling transistor and a control terminal of the cross-coupling transistor of the second amplifier circuit. The second coupling circuit including a capacitor and a coupling transistor, the second coupling circuit being connected such that a control terminal of the coupling transistor is connected to the second input signal node and the capacitor is connected between a first output terminal of the coupling transistor and a control terminal of the cross-coupling transistor of the first amplifier circuit."

URL and more information on this patent, see: Straub, Michael; Krebs, Andrew P.. High Impedance Low Noise Cross-Coupled Amplifier for Use in as a Preamplifier in a Magnetic Data Storage System. U.S. Patent Number 8792198, filed December 27, 2013, and published online on July 29, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8792198.PN.&OS=PN/8792198RS=PN/8792198

Keywords for this news article include: LSI Corporation, Information Technology, Information and Data Storage.

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Source: Information Technology Newsweekly


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