Abstract: The present invention relates to an amplifier intended to deliver to a load impedance RL connected between two output terminals of the amplifier an output current Iout which is representative of an input signal (Vin, ?Vin) applied to two input terminals of the amplifier, which amplifier includes a first and a second transistor T1 and T2 connected as a differential pair around the load impedance RL. The amplifier according to the invention further includes a third and a fourth transistor T3 and T4 which form a differential pair; degenerated by means of a degenerating impedance Req which has a nominal value equal to that of the load impedance RL of the amplifier, which differential pair (T3, T4) is intended to be controlled by means of a control signal (?Vin/2, Vin/2), in anti-phase with the input signal (Vin, ?Vin). The invention permits to double the output current Iout of the amplifier without, however, increasing its power consumption.

Abstract: A method and system are disclosed for providing a variable speed digital read channel. The read channel includes an analog portion and a digital portion. The read channel includes an analog-to-digital converter (ADC) for converting an analog read signal into a sampled read signal. The ADC is synchronized to a sample clock. The sample clock has a variable clock rate. The digital portion includes a digital filter for reducing noise. The digital filter can be implemented as a low pass filter (LPF), a high pass filter (HPF), or a bandpass filter (BPF). The filter receives the sampled read signal from the ADC. The digital filter is synchronized to the sample clock. The digital filter's cutoff frequencies adjust automatically as the variable clock rate is changed, and does not require reprogramming. The digital portion may also include a digital automatic gain control device.

Abstract: A method and apparatus for detecting a topographic feature on a media is described. More particularly, a light scatter detector is coupled to an atomic force microscope. The detector is used detect scattered optical energy reflected from the surface of the media to identify the topographic feature. The atomic force microscope may then be positioned in response to the topographic feature identified.

Abstract: A system and method for incrementally recording blocks of data such as servo information on magnetic media such as hard disks, flexible disks or tapes. The system comprises a master element with permeable features configured according to the block of data and corresponding to a small fraction of the area of the medium. A predetermined portion of the medium is advanced and brought in proximity to the master element. An electromagnet applies a localized field to copy the data to the selected portion of the medium. The field of the electromagnet is decreased before the next predetermined portion of the medium is advanced thereby avoiding damage to previously recorded data.

Abstract: A magnetic transfer apparatus for magnetically transferring information represented by a pattern of a magnetic layer formed on a master information carrier to a slave medium includes a magnet unit which applies an initial DC magnetic field to a slave medium and a magnet unit which applies a transfer magnetic field to the slave medium and the master information carrier in the direction opposite to the direction of the initial-magnetization with the slave medium held in close contact with the master information carrier. The initial DC magnetic field and the transfer magnetic field are not larger than the diameter of an innermost recording track in the half-width of a curve representing an intensity distribution in the direction of a tangent of the innermost recording track.

Abstract: The present invention is directed to detecting amplitude modulation on the written signal as a result of head movement along the z-axis during the write operation, before the head has had sufficient time to stabilize after seeking from a different track.

Abstract: An improved bias circuit for a disk drive head which reduces or eliminates transients while switching biasing. Embodiments of the invention are directed to eliminating transients while switching the bias of a MR head such as from current bias to voltage biasing. In an embodiment of the present invention, bias enable signals from a control circuit are inputs to delay circuits. The delay circuits provide a delay on the high-to-low transition, and essentially no delay on the low-to-high transition. The unsymmetrical delay ensures that the read head bias current will continue to be driven during the biasing transition to reduce voltage swings that could damage the head.

Abstract: A clogging detector used for a VTR to check the recording state of a recording head without using the reproducing head. A test signal of a lower frequency than the erasing frequency is recorded before and after an information signal by means of an erasing head. Before and after recording the information signal by means of the recording head, the test signal is reproduced, the reproduction output is detected by a detecting circuit, and the level of the output is compared with a preset level by a comparing circuit. When the level is lower than the preset level, a warming is issued from a warming circuit, thus preventing a recording failure due to the clogging of the head.

Abstract: Disk drives are produced having a track density that is determined during a servo-track writing operation. A plurality of calibration tracks is written onto a storage medium of a disk of a head-disk assembly at a calibration track density. The calibration track density corresponds to a portion of a nominal track density profile. An aspect of the servo performance of the head-disk assembly is measured at the calibration tracks. A selected track density profile is identified based on the measured servo performance. The plurality of tracks is written to storage medium at the selected track density profile.

Abstract: To improve the track density by reducing the discontinuity of servo patterns to be generated by a servo track writer, some servo areas existing in one circuit of a magnetic disk are formed at the consecutive first and second circuits of a servo track writer by averaging a plurality of position signals detected from servo patterns at the first and second circuits of the magnetic disk.

Abstract: When, through a multi-speaker of a DVD audio system, signals are recorded/reproduced using a sampling frequency different for every channel, the quantity of calculation of a filter circuit is reduced. Up-sampling information about whether or not the sampling is carried out before the up-sampling by up-sampling means (2a, 2b) is acquired by up-sampling information detecting means (6). The signal up-sampled is filtered by a halfband filter circuit (3), subjected to loss-less compression, and recorded on a recording medium (8).

Abstract: A disk drive contains at least one sector that is protected from erasure, such as an erasure that may occur during reformatting. The sector(s) is used to store information related to one or more tests that may be performed on the disk drive and/or on other devices of a computer system in which the disk drive is located. This information may be used to facilitate a subsequent evaluation of the disk drive and/or computer system.

Abstract: Monitoring the decay of the magnetic domains and refreshing the magnetic domains when the amount of decay has passed an established threshold allows a means to compensate for the superparamagnetic effect and increase the amount of data stored on a recording media. A high frequency reference signal and a low frequency reference signal can be written onto the magnetic media. The low frequency reference signal corresponds to large magnetic bits on the storage media surface, whereas the high frequency reference signal corresponds to small magnetic bits. Because of the large difference in decay rates between the high frequency and low frequency reference signals, any change in the difference of the two signals over time actually reflects the level of signal degradation that has occurred in the high frequency reference signal.

Abstract: A high-performance head positioning control system composed of a suitable combination of a multi-rate control system and a single-rate control system has been disclosed. An SM judging unit selects the multi-rate control system in a seek operation in which the head is moved to the desired track on the disk. When the head has come close to the desired track and changes from seek control to track following control, the SM judging unit switches from the multi-rate control system to the single-rate control system. The single-rate control system performs track following control whereby the head is positioned in the range of the desired track.

Abstract: According to a broad aspect of the invention, a method and apparatus are presented for identifying a track (42) of a rotating disk (12) of a mass data storage device (10), using EPR4 data detection techniques. The track identification indicia (64) may be written more densely than the track identification indicia would have been written without using EPR4 data equalization techniques, wherein track identification indicia pulses (110-113) may at least partially overlap. The identification indicia (110-113) is read from the disk (12) using a read head (18), and processed using EPR4 data equalization techniques in an EPR4 Viterbi detector (92). The Viterbi detector (92) may be used also to detect data pulses (64) by switching its mode of operation from a track identification mode to a data detection mode.

Abstract: A circuit (80) and method (84) for protecting read heads (18) of a hard-disk drive system (100). Capacitor C1 is controllably coupled to a dummy head Rdummy during a Vbias mode, so that capacitor C1 has a low, predictable voltage upon returning to Ibias mode, protecting the read heads (18) from damage. The circuit (80) includes logic (82) and algorithm (84) determining when to couple the capacitor C1 to the dummy head Rdummy during a servo bank write (SBW) sequence.