# US 6,724,551 B2 · Preamp fast head switch technique for servo mode

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- Number: US 6,724,551 B2
- Document ID: US6724551B2
- Status: Granted
- Kind: B2
- Application number: 09/895,909
- Filed: 2001-06-29
- Published: 2003-01-02
- Granted: 2004-04-20
- Earliest claimed: 2001-06-29
- Assignees: Texas Instruments Incorporated
- Inventors: Indumini W. Ranmuthu
- Web page: https://patentgrep.com/patent/US6724551B2

## CPC

- G11B 5/40: Protective measures on heads, e.g. against excessive temperature (G11B5/31 takes precedence; protection against wear G11B5/255 {; protective structure of the head: see under structures, e.g. G11B5/3106})
- G11B 5/012: Recording on, or reproducing or erasing from, magnetic disks (G11B17/00, G11B19/00 take precedence)
- G11B 2005/0013: {of transducers, e.g. linearisation, equalisation}
- G11B 2005/0016: {of magnetoresistive transducers}
- G11B 2005/0018: {by current biasing control or regulation}
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)

## Abstract

A differential circuit to read differential data from a disk by a current bias on a plurality of read heads includes a read circuit to read the differential data from the disk by maintaining the current bias. The current is below a maximum current of a read head having the lowest maximum voltage of said plurality of read heads.

## Claims

### Claim 1

A differential circuit to read differential data from a disk by a current bias on a plurality of read heads, comprising:
a read circuit to read said differential data from said disk by maintaining said current bias on said read head by maintaining a single safe current in each of said plurality of heads; and
wherein said safe current is below a maximum current of all said plurality of read heads.

### Claim 2 (depends on 1)

A differential circuit, as in claim 1, wherein said safe voltage is maintained across a capacitor of said read circuit.

### Claim 3

A differential circuit to read differential data from a disk by a current bias on a plurality of read heads, comprising:
a read circuit to read said differential data from said disk by maintaining said current bias on said read head by maintaining a safe current; and
wherein said safe current is below a maximum current of all said plurality of read heads,
wherein a head switching time of said read circuit is a less than 500 ns.

### Claim 4

A disk system to read information from a disk, comprising:
a read/write head to read and write information from said disk;
a read channel to process said information; and
a differential circuit to read differential data from a disk by a current bias on a plurality of read heads during servo write module, comprising:
a read circuit to read said differential data from said disk by maintaining said current bias on said read head by maintaining a single safe current in each of said plurality of heads; and
wherein said safe current is below a maximum current of all said plurality of read heads in frequency.

### Claim 5 (depends on 4)

A disk system as in claim 4, wherein said safe voltage is maintained across a capacitor of said read circuit.

### Claim 6

A disk system to read information from a disk, comprising:
a read/write head to read and write information from said disk;
a read channel to process said information; and
a differential circuit to read differential data from a disk by a current bias on a plurality of read heads during servo write module, comprising:
a read circuit to read said differential data from said disk by maintaining said current bias on said read head by maintaining a safe current; and
wherein said safe current is below a maximum current of all said plurality of read heads in frequency
wherein said a switching time of said read circuit is a less than 500 ns.