Abstract: A method for manufacturing a hard disk drive is described. The method includes providing a motor assembly, the motor assembly comprising a stationary portion and a rotatable portion for rotating a magnetic disk with respect to said stationary portion and providing a base for receiving the motor assembly. The method further includes providing an adhesive for mounting the motor assembly to said base wherein the adhesive is electrically conductive and mounting the stationary portion of the motor assembly to the base utilizing the adhesive such that the adhesive provides a low resistance path between the base and the motor assembly.

Abstract: Magnetic sensing chips and methods of fabricating the magnetic sensing chips are disclosed. A magnetic sensing chip as described herein includes an EMR sensor formed on a substrate from multiple semiconductor layers. One or more of the semiconductor layers form a quantum well comprising a two-dimensional electron gas (2DEG) or hole gas (2DHG). The magnetic sensing chip also includes one or more transistors formed on the substrate from the multiple semiconductor layers. The transistor(s) likewise include a quantum well comprising a 2DEG or 2DHG. The EMR sensor and the transistor(s) are connected by one or more connections so that the transistor(s) amplifies data signals from the EMR sensor.

Abstract: A method for manufacturing a hard disk drive is described. The method includes providing a motor assembly, the motor assembly comprising a stationary portion and a rotatable portion for rotating a magnetic disk with respect to said stationary portion and providing a base for receiving the motor assembly. The method further includes providing an adhesive for mounting the motor assembly to said base wherein the adhesive is electrically conductive and mounting the stationary portion of the motor assembly to the base utilizing the adhesive such that the adhesive provides a low resistance path between the base and the motor assembly.

Abstract: Magnetic sensing chips and methods of fabricating the magnetic sensing chips are disclosed. A magnetic sensing chip as described herein includes an EMR sensor formed on a substrate from multiple semiconductor layers. One or more of the semiconductor layers form a quantum well comprising a two-dimensional electron gas (2DEG) or hole gas (2DHG). The magnetic sensing chip also includes one or more transistors formed on the substrate from the multiple semiconductor layers. The transistor(s) likewise include a quantum well comprising a 2DEG or 2DHG. The EMR sensor and the transistor(s) are connected by one or more connections so that the transistor(s) amplifies data signals from the EMR sensor.

Abstract: An integrated transducer-electronics interconnection suspension for a disk drive having a high data transfer rate generally above 15 Mbytes/sec between the transducer and the read/write electronics. A suspension supports a slider to which a transducer is mounted and maintains the slider in close proximity to the disk surface. An integrated transducer-electronics interconnection suspension is a laminate structure having electrically conductive traces as part of the structure and connecting the transducer with the read/write electronics. It can support high data transfer rates between the transducer and the read/write electronics by avoiding sudden changes in the characteristic impedance of the traces to minimize signal reflection on them. The width of the traces are shaped accordingly to prevent abrupt changes in the trace impedance caused by trace bonding areas, apertures and other mechanical obstructions in the suspension. Changes in the traces' direction are gradual to avoid signal reflection.

Abstract: A disk drive power manager that compares energy usage with a predetermined profile to select one of several reduced-power operating modes. An energy usage register is updated at regular intervals according to the energy used during each time interval. An attenuated average energy usage value is obtained by attenuating the energy usage measures over time and integrating the results. The average energy level is compared with several predetermined energy threshold profiles to select a full- or reduced-power operating mode. Operating mode selection automatically adapts to the usage pattern to optimally balance power consumption with operational accessibility.

Abstract: A disk drive power manager that compares energy usage with a predetermined profile to select one of several reduced-power operating modes. An energy usage register is updated at regular intervals according to the energy used during each time interval. An attenuated average energy usage value is obtained by attenuating the energy usage measures over time and integrating the results. The average energy level is compared with several predetermined energy threshold profiles to select a full- or reduced-power operating mode. Operating mode selection automatically adapts to the usage pattern to optimally balance power consumption with operational accessibility.

Abstract: A disk drive power manager that compares energy usage with a predetermined profile to select one of several reduced-power operating modes. An energy usage register is updated at regular intervals according to the energy used during each time interval. An attenuated average energy usage value is obtained by attenuating the energy usage measures over time and integrating the results. The average energy level is compared with several predetermined energy threshold profiles to select a full- or reduced-power operating mode. Operating mode selection automatically adapts to the usage pattern to optimally balance power consumption with operational accessibility.

Abstract: A data storage system comprises magnetoresistive (MR) sensing elements for sensing data from a recording medium that is referenced to ground, and an amplifier circuit including a biasing stage, an amplifying stage, and a matching stage, each referenced to a common supply voltage source and to ground. The biasing stage includes a reference current source for selectively biasing each MR element with a constant current and, in so doing, developing a single-ended voltage signal having a first dc component. The amplifying stage converts the single-ended voltage signal into an amplified single-ended output voltage signal having a second dc component but in which the first dc component is eliminated. The matching stage creates a bias and imposes said bias on the amplifying stage for converting the single-ended output voltage signal to a differential output voltage signal in which the second dc component is eliminated.

Abstract: Low noise, low power, low voltage amplifier circuits with a single ended input having no common mode rejection for concurrently biasing and amplifying signals generated by magnetoresistive (MR) elements in a disk file. The amplifier circuits comprise a single (grounded) supply voltage source. One terminal of each MR element and the conductive substrate of each MR element and the conductive substrate of each disk in the disk file are grounded to minimize transient conductive asperity currents. The head/disk assembly of the disk file is completely enclosed by a highly conductive electrostatically shielded metallic enclosure that operates as a Faraday cage and isolates leads connecting the MR elements with the amplifier circuit from large, fast rise/fall time voltage transients.

Abstract: A magetic recording system includes a current-tapering circuit which gradually reduces the WRITE current in a magnetic recording head to zero over a time interval on the same order of magnitude as the characteristic relaxation time of the domain patterns in the magnetic recording head, rather than abruptly. Specific embodiments of the current-tapering circuit create a down-sloping ramp, a decaying exponential curve, and a high-frequency burst. The resultant magnetic recording system has reduced Barkhausen noise and reproducible READ performance as well as improved READ sensitivity following a WRITE operation.

Abstract: A method and circuitry are described for sensing the clearance between a magnetic transducer and a moving magnetic recording medium in a magnetic disk or tape storage system or alternatively sensing the degree of magnetic instability of a magnetic transducer in such a system. Magnetic transitions prewritten on a preselected area of the medium are read to obtain a readback signal. The width of said signal is sensed at a predetermined amplitude level which is a preselected percentage of its base-to-peak amplitude to provide a voltage corresponding to the width of said signal at said level. The voltage is proportional to the width of the readback signal divided by the time period between successive transitions of identical polarity, so as to provide a measurement of clearance of degree of magnetic instability that is independent of the relative velocity between said transducer and medium.The voltage is digitized and compared to a prestored digital reference value.

Abstract: An amplifier circuit is disclosed for simultaneously producing electrical output signals whose magnitude is representative of signals produced by a magnetoresistive (MR) element and protecting said MR element from electrical short circuits between said element and its environment. A means including a first feedback loop biases the MR element with a bias current and amplifies a signal current for causing the MR element to produce a circuit output signal corresponding to dRh/Rh and in which any dc offset error is minimized. Rh is the resistance of the MR element and dRh is the magnetic-signal-induced change in the resistance of the MR element. A second feedback loop insures that the MR element is held at a preselected reference potential and concurrently insures that no current will flow sufficient to damage the element in event of a short circuit between the element and its environment.

Abstract: A method and circuitry for suppressing additive transient disturbances in an analog differential input signal, such disturbances being due, for example, to thermal asperity transients caused by an MR transducer contacting a moving storage surface. The input data signal is algebraically summed with a corrective feedback signal for providing as output signal. The output signal is fed back to a circuit including an envelope detector and differentiator and converted into another signal that is the derivative of an amplitude envelope corresponding to the output signal. Nonlinear signal-adaptive filter means converts said other signal into the corrective feedback signal, which substantially replicates the additive transient disturbance and is subtracted from the data input signal to render the output signal substantially free of the transient disturbance.The input, output and corrective signals are preferably differential signals.

Abstract: A circuit for producing a signal whose magnitude is a chosen amplitude compensation characteristic of the signals produced by a magnetoresistive (MR) element comprising an input stage which produces an amplified output signal which is coupled to the output stage, and control signals proportional to the resistance of the MR element and inversely proportional to the resistance of the MR element which are coupled to a feedforward circuit. The feedforward circuit generates a chosen amplitude equalization characteristic of the signals coupled to the feedforward circuit, and this signal is coupled to a bias terminal of the output stage so that the output stage produces a signal representing the chosen amplitude compensation characteristic of the signals produced by the MR element.

Abstract: A method and circuitry are disclosed for suppressing additive transient disturbances in a data channel; e.g., due to thermal transients caused by an MR transducer contacting moving a storage surface. Positive and negative envelope detectors each have their inputs connected to the channel, and provide respective outputs which are summed and contain an envelope component and a residue component. A buffer interconnects the detectors to allow both detectors to follow rapid positive excursions of the data channel signal. A nonlinear signal-adaptive filter is connected to the summed output to further reduce the residue component. The data channel signal (or preferably the output from a delay means connected to the channel) is summed with the output from the filter. The relative amplitudes of these two outputs is set such that the resulting summed output signal is free of additive disturbances.

Abstract: A protective circuit for a magnetoresistive (MR) element having a first and a second terminal in which a first current source is coupled to the first terminal of the MR element to produce a bias current through the MR element and a second current source is coupled to the second terminal of the MR element to produce a reference current. Circuit means coupled across the MR element senses the center potential of the MR element substantially midway between the first and second terminals, and a feedback circuit responsive to the sensed center potential is coupled to adjust the current output of the first current source to maintain the center potential to a selected reference voltage to protect the MR element from short circuits to a conductive area of the magnetic recording medium.

Abstract: An amplifier for voltage biasing and amplifying the signals produced by a magnetic sensor is provided. Electrically, the resistance of the sensor is disposed between the bases of a differential pair comprising the input stage of the amplifier. Constant bias voltage for the sensor is provided independently of sensor resistance. DC feedback to the input stage balances current flow in both paths of the differential input stage to correct for DC offset arising in the output from input stage emitter resistor. The amplified signal, representing .DELTA.R.sub.h /R.sub.h, is sensed as a voltage across the magnetoresistive sensor, where .DELTA.R.sub.h is the change in steady-state resistance, R.sub.h, of the sensor.

Abstract: A method and apparatus for measuring the flying height of a slider supporting a magnetic transducer in-situ in a direct manner in an operational magnetic disk storage system. The method and apparatus produce relative motion between the magnetic transducer and a magnetic recording medium at a first velocity so that the resulting air bearing positions the magnetic transducer slider at a first flying height from the magnetic medium. A single signal of constant periodicity is written over a predetermined area of the recording medium by the magnetic transducer, and a readback signal is sensed from the predetermined area of the recording medium to produce a first signal. The flying height of the magnetic transducer slider is lowered to substantially zero, and a readback signal is sensed at the lowered flying height to produce a second signal. The first flying height is then calculated as the ratio, expressed in decibels, of the first and second signals times the wavelength divided by a constant.

Abstract: A frequency response compensation circuit includes a first forward gain stage and second reverse gain stage coupled to the first stage in negative feedback mode. The reverse gain stage depresses the gain of the first stage at low frequencies. When the frequency response of the reverse gain stage begins degrading, which corresponds to the frequency of the real zero of the compensation circuit, the gain of the compensation circuit begins increasing and increases until the gain of the reverse stage is zero. The circuit utilizes a pair of NPN transistors in the first stage, a pair of PNP transistors in the second stage and includes no capacitors or inductors. Thus, the circuit can be implemented as a semiconductor integrated circuit. By proper selection of the resistance values of the resistors in the circuit, the zero of the compensation circuit can be chosen to correspond generally to the frequency of the pole of the uncompensated input signal, so as to increase the bandwidth of the resultant signal.