Abstract: A hard disk drive system (10) includes a read/write head (21) for reading and writing data to and from a rotating magnetic disk (12). The read/write head includes a portion which is a magneto-resistive read head (36), the output of which is supplied through a preamplifier (26) to a read channel circuit (27). The read head has a nonlinear transfer function. The read channel circuit includes an asymmetry compensation circuit (62), which generates an analog compensation signal by squaring an output signal from the read head and scaling by an asymmetry factor (.alpha.'). The analog compensation signal is combined with the analog output signal in order to obtain a corrected analog signal, which is substantially free of the distortion introduced by the read head.

Abstract: A magnetic recording and regenerating unit for photographic film and a camera, which feed photographic film coated with a magnetic recording layer, records magnetic information in the magnetic recording layer, and regenerates magnetic information from the magnetic recording layer. In the magnetic recording and regenerating unit for a camera, the number of turns of a coil wound around a core included in a magnetic head is small. Thus, one magnetic head is able to record and regenerate magnetic information. The number of turns of the coil is determined so as to output a regenerated waveform which does not enable reading of the magnetic information but permits determination of whether any magnetic information is recorded or not. Whether any magnetic information is recorded or not is determined based on the output voltage from a smoothing circuit, a peak hold circuit, etc. which receive signals output from the magnetic head via an amplifier.

Abstract: A system and method for an amplifier control circuit is provided which does not require the use of a large off-chip or on-chip capacitor for achieving a low frequency coupling corner, while still effectively allowing AC coupling the data detection circuit. In addition, the input offset voltage to the amplifier may be compensated and the inherent random low frequency input voltages provided to the amplifier may be controlled or canceled. Further, the amplifier control circuitry includes a freeze capability which allows the control circuitry to halt all updates to the input offset/low frequency control circuit when the voltage input signal is interrupted. In addition low frequency control and offset compensation updates may be performed without causing large output signal glitches so that the integrity of the received signal will not be compromised. In a preferred embodiment the system and method may be utilized for data detection circuits utilized in conjunction with optical disks.

Abstract: An automatic gain control circuit, for amplifying an input signal so that it has a specific correspondence with a reference value (V.sub.ref), includes an input terminal (2) for receiving the input signal, a variable gain amplifier (4) for amplifying the input signal in response to a gain control signal, a peak detector (14) for detecting peaks in the amplified input signal, the peak detector (14) having an attack time constant (T.sub.a) and a decay time constant (T.sub.d), and supplying a peak detector output signal (V.sub.p) representative of the amplitude of the peaks in the amplified input signal, a comparator (20) for comparing the peak detector output signal (V.sub.p) with the reference value (V.sub.ref) to form an error signal (e), and an integrator (30) for integrating the error signal (e) to form the gain control signal.

Abstract: A current bias, current sense magneto-resistive preamplifier for a hard disk drive and related methods preferably includes an MR sensor responsive to a current bias for sensing a change in magnetic data flux and responsively providing a change in electrical resistance. A preamplifying circuit is preferably connected to the MR sensor for providing the current bias thereto and for amplifying a detected change in electrical resistance. The preamplifying circuit includes a sensor biasing circuit for providing the current bias to the MR sensor and an amplifying output circuit for providing an amplified output signal representative of the detected change in current bias to the MR sensor. The sensor biasing circuit preferably includes a current source, a first amplifying circuit connected to the MR sensor for sensing the change in electrical resistance therefrom, and a second amplifying circuit having a first input connected to the first amplifying circuit and a second input connected to the current source.

Abstract: A thermal asperity detection method includes the steps of (a) converting an analog signal reproduced from a magnetic recording medium into a digital signal using an analog-to-digital converter, (b) detecting thermal asperity based on the digital signal, and (c) automatically recognizing and managing detection of the thermal asperity by the step (b) by firmware.

Abstract: An apparatus and method for sensing and reporting connection integrity of a differential transmission line having proper parallel termination is constructed by generating an error signal which indicates that one or both differential input lines are open. The error signal is generated using a voltage comparator having a first and second input in which these inputs are coupled to the first and second ECL signal lines. The first and second input lines are also coupled to a supply voltage by a first and second dynamic impedance such that the input is pulled high when the signal lines are open. The comparator generates an error signal when the input voltages are greater than voltages normally seen on the signal lines indicating the presence of a open transmission line.

Abstract: A magnetic disk drive includes a circuit portion having transfer characteristics for determining low-frequency cutoff characteristics in a transfer line ranging from a signal output terminal P1 of a head to a branch portion P2 between a data demodulation circuit and a servo demodulation circuit, and an equalization circuit having transfer characteristics having the relation of an inverse function to low-frequency portion of the transfer characteristics between P1 and P2, disposed in the transfer line ranging from the branch portion to the servo demodulation circuit. This circuit constitution can reduce waveform distortion of servo signals at the time of reproduction and can improve the positioning accuracy of the head.

Abstract: A method and system for detecting common mode disturbances from a magnetic recording head having dual magnetic recording elements. An electrical current is supplied to both of the dual magnetic recording elements within the magnetic recording head. Thereafter, the electrical current is shunted through only one of the dual magnetic recording elements. A voltage signal is then detected across the dual magnetic recording elements, which occurs in response to the shunting of the electrical current through only one of the dual magnetic recording elements. Finally, the voltage signal is analyzed for indications of common mode disturbances accentuated as a result of the shunting of the electrical current through only one of the dual magnetic recording elements. Common mode disturbances that can be detected include thermal asperities.

Abstract: Apparatus and method for dynamically programmiing the magnitude of read bias and write currents in a disc drive head. A digital input value is provided to a register of a digital to analog converter, the digital input value indicative of the desired magnitude of the head current. A multiplier of the digital to analog converter multiplies the digital input value by a reference voltage to generate an output voltage. The differential voltage between the reference voltage and the output voltage controls the source to drain resistance of a transistor connected in series with a preamp voltage source of a preamp circuit. By inputting different digital input values, the source to drain resistance of the transistor, and hence the magnitude of the current generated by the preamp voltage source, are precisely controlled. The magnitude of the head current is provided as a multiple of the magnitude of the current generated by the preamp voltage source.

Abstract: A multi-head, disc drive, of a data storage system having a preamplifier that is split into a mother chip and set of daughter chips, each daughter chip corresponding to a head in the disc drive. The daughter chips contain very little circuitry, typically just a write driver, the front end of a read amplifier, a write fault detector, and a bias control circuit. Because the daughter chip contains little circuitry, it can be made much smaller and lighter than a conventional preamplifier, allowing the daughter chip to be placed on the suspension, close to the head. This allows the signal sent to and received from the head associated with a daughter chip to be strong enough not to be corrupted during transmission to the circuitry in the rest of the preamplifier. It also increases the bandwidth and reduces the power consumption of the preamplifier. The mother chip contains the remaining circuitry needed in the preamplifier and can be placed farther away, on a portion of the HSA that can support a larger chip.

Abstract: A signal reproducing circuit for a magneto-resistive effect head includes a constant current source for supplying a sense current to an MR head in a read state, first constant current sources for supplying first constant currents to a pair of reproduction transistors in the read state, and a capacitor connected between the emitters of the transistors. Furthermore, second constant current sources for supplying second constant currents are connected in parallel with the first constant current sources. Control is given so that when switching an idle state to the read state is commanded, the second constant current sources remain on for a given period of time. Owing to this circuitry, a transient period during which the idle state is switched to the read state or a transient period during which heads are switched in the read state can be shortened to a great extent.

Abstract: A very-small-signal amplifier is capable of amplifying very small signals with high sensitivity up to high frequencies while simplifying the circuit, and a magnetic disk storage apparatus realizes a reading operation over a wide band up to high frequencies with high sensitivity. The signal amplifier is a modified differential circuit including a first transistor of a first conductivity type and a second transistor of a second conductivity type each having a control terminal, a terminal of the input side and a terminal of the output side. The terminals on the input side are connected in common, and a current corresponding to the voltage difference across the control terminals is allowed to flow. A very small voltage signal generated by an input signal source is applied to the control terminal of said first transistor. A bias voltage is applied to the control terminal of the second transistor.

Abstract: The present application discloses an electronic switching device in combination with a low noise, low input impedance preamplifier circuit. The resulting electronic preamp assembly is specifically configured so that it can be directly interchanged with existing mechanical relay/preamplifier assemblies such as those presently in use in recorder/reproducer apparatus having dual function record/playback heads, without disturbing the associated operating parameters of the record or playback channels. The electronic preamp assembly includes a balun transformer and a solid state switch coupled from a record amplifier to the record/playback head via a rotary transformer to define the record channel. The playback channel includes a diode bridge switch and a preamp circuit also coupled to the rotary transformer and head.

Abstract: A disk drive comprising a plurality of read/write transducers, a programmable preamplifier, and a controller for furnishing control and data signals to the programmable preamplifier and for receiving data signals therefrom, is disclosed. The programmable preamplifier comprising a write data input circuit for receiving data signals to be supplied to a transducer, a read data output circuit for manifesting data signals supplied to said preamplifier unit by a transducer, and a transducer interface circuit for providing write data signals to a transducer and receiving read data signals from a transducer.

Abstract: A magnetoresistive sensor and preamplifier system for sensing magnetization patterns in a magnetic disk based digital data storage and retrieval memory with a grounded magnetoresistive sensor The signals from the magnetoresistive sensor are coupled by a coupling capacitor to a grounded differential amplifier. The structure of the coupling capacitor in a monolithic integrated circuit determines the passband for the system in passing the magnetoresistive sensor signals.

Abstract: An MR head circuit including a differential amplifier, means for applying a dc bias to the head, a capacitor mounted in parallel to the head to eliminate the dc voltage offset, and a feedback loop configured for evaluating the differential voltage and for controlling the current in portions of the amplifier to rapidly charge the capacitor upon circuit activation. The feedback loop also includes a thermal asperity compensator configured for producing a given signal, both upon activation of the circuit and when the magnitude of the voltage differential exceeds a given value, and the feedback loop includes means responsive to the given signal for altering select current paths of the feedback loop to thereby produce elevated charging currents in the differential amplifier during initial activation, and to increase the ac gain of the feedback loop at other times so as to raise the lower corner frequency of the differential amplifier to filter out the relatively low frequency of a thermal asperity waveform.

Abstract: A preamplifier circuit couple to a magneto-resistive (MR) head used in the read circuitry of a magnetic storage device includes differential amplifiers coupled to receive an input from the MR head and to provide output signals. The preamplifier is designed to provide a low noise level. To minimize noise, transistors of the differential amplifiers provide high current gain and have large device geometries.

Abstract: A magnetoresistive transducer biasing technique that provides a uniform transducer biasing in a product. The technique provides biasing for transducer constant power dissipation, constant sensor current density biasing, constant sensor bias voltage, constant sensor temperature rise biasing, and constant effective magnetic biasing of a transducer.

Abstract: A circuit for detecting a disturbance signal in an information signal for a read channel circuit includes a resistor connected to ground and a capacitor to form an RC circuit to detect the disturbance. The read channel receives the information signal and the detection signal.

Abstract: A read/write head for a magnetic medium magnetic is modified by the addition to it of a parallel-connected resistor and by the measurement of the difference in voltage at the terminals of this unit, on the one hand when the read/write head and the resistor are perfectly connected and, on the other hand, when one of the connections is in an open circuit condition or even in short-circuit condition with respect to ground. Consequently, a measurement is taken, preferably, of the state of connection of the read/write head when it is in read mode and not when it is in write mode. It is shown that far greater reliability in the detection of this type of defect is obtained, in avoiding false alarms.

Abstract: Real-time gain control calibration is provided for each frequency of a disk drive storage system using dual-frequency, dual-burst position error sensing (PES) signals. Automatic and independent gain control for each PES servo burst frequency component is achieved with an automatic gain control (AGC) mapping that determines the approximate head position and performs an appropriate gain calibration for each servo burst frequency or with sector by sector normalization performed for each PES signal sample. For the AGC mapping, calibration is performed either with calibration tracks or with an in situ method. Both mapping and normalization methods provide accurate automatic gain calibration during signal readback.

Abstract: A process and device are disclosed for reading weak magnetically recorded signals from a photographic film provided with a transparent thin magnetic layer. The signals from a magnetic read head obtained from the moving film are pre-amplified and the pre-amplified signals are digitized, filtered, differentiated and evaluated. The output of the magnetic read head (2) is supplied to the pre-amplifier (5) in short-circuit. This means that the internal resistance R.sub.i of the magnetic head is very high compared to the input resistance R.sub.e of the amplifier connected immediately downstream of the magnetic read head coil.

Abstract: A write amplifier is provided with one or more improved switching performance, low output common-mode voltage, and precise write head current control. A low output common-mode voltage is achieved using a combination of circuit components which limit the undesirable delivery of current from a differential pair of transistors used for switching, or steering, the current delivered to the write head. Additionally, a voltage source within the amplifier precisely controls the write current delivered to the differential pair.

Abstract: A system for providing feedback to a selected read head in a multi-head disk drive includes first and second feedback circuits is disclosed. A first feedback circuit 200 provides for correction of the output of the selected read head during normal operation. The first feedback circuit 200 produces a differential output current proportional to an offset voltage detected on the read head output nodes 103 and 104. This differential output current charges external capacitor 190. The voltage across capacitor 190 is supplied to voltage inputs of the selected read head as a feedback voltage. When the feedback voltage reaches the desired level, nodes 103 and is 104 equalize, as do the output currents of the first feedback circuit 200. The second feedback circuit 300 provides for quick recovery of the system after a change in read heads.

Abstract: A low noise current source circuit is disclosed for biasing a magnetoresistive (MR) read head. The current source comprises a field-effect transistor (FET) cascoded to a second transistor which, in turn, is coupled to the MR element. A filter device including a capacitor is coupled across the gate-source junction of the FET, and a sensing device, such as a resistor, is coupled to the gate of the FET for detecting current flowing into said capacitor. Boost circuitry, coupled to the sensing device, boosts the charge/discharge rate of the filter capacitor when the voltage of the sensing device exceeds a certain threshold.

Abstract: An apparatus and associated method are disclosed for recovering user data from a data block in a disc drive in which user data are stored by way of a plurality of blocks on tracks of a disc, the blocks including data blocks in which the user data are stored in predefined increments. A head generates readback signals from the blocks and a read channel reconstructs the user data from the readback signals. An automatic gain control stage establishes a gain used to amplify the readback signal to a level suitable for use by the read channel. When an uncorrected read error is detected, the disc drive proceeds to read a previous block sequentially preceding the affected data block and sets the gain to a fixed value based upon the readback signals determined from the previous block. The fixed value of gain is then used to recover the user data from the affected data block.

Abstract: An improved thermal asperity detector is disclosed for detecting short thermal asperities using a variable time threshold. The thermal asperity detector includes a saturation detector, and a comparator system. The comparator system may include a polarity latch, a processor, a level comparator and a timing comparator. The saturation detector compares a programmable saturation threshold to an A/D sample to generate an enable signal in response to the A/D sample exceeding the saturation threshold. The polarity latch receives the A/D sample and the enable signal, and records the most significant bit of the A/D sample to identify the polarity of the saturation and to provide an output signal representative thereof in response to the enable signal. The processor generates a threshold level control signal based upon a programmable level threshold and the polarity latch output signal.

Abstract: A method for generating a response in a transconductance circuit includes receiving a circuit differential voltage input and providing a differential voltage input to each of a plurality of differential pairs to control, in part, a differential current generated by each differential pair. Each differential voltage input has a different common-mode voltage level. The method also includes sinking current through each of the differential pairs to control the differential current generated by each differential pair. The magnitude of the current sunk through one of the differential pairs is different from the magnitude of the current sunk through at least one of the other differential pairs. The method also includes combining the generated differential current from each of the plurality of differential pairs to produce a differential current output.

Abstract: On an FCP board and in a head amplifier circuit, provided for amplifying a read signal from a head and supplying the read signal to a read channel, a dummy wiring pattern is located near a wiring pattern for supplying the read signal. The head amplifier circuit incorporates a differential amplifier. The differential amplifier finds and amplifies a difference between the read signal supplied through the wiring pattern and the noise signal supplied through the dummy wiring pattern. The differential amplifier outputs to a read channel the read signal from which the noise has been removed.

Abstract: In a magnetic disk apparatus performing a positioning operation in a sector servo system, an AGC amplification gain measuring circuit measures an amplification gain of an AGC amplifier on the basis of the reproduction of a magnetic pattern in an AGC region within a servo area of a magnetic disk. An AGC amplification gain judgment circuit judges whether the value of the amplification gain measured by the AGC amplification gain measuring circuit is out of a set range, and outputs the judgment result. When receiving from the AGC amplification gain judgment circuit a judgment result indicating that the value of the amplification gain is out of the set range, a recording/reproducing operation control circuit stops the recording operation of a recording circuit.

Abstract: A method and a circuit for correcting asymmetry in a response signal generated by a magneto-resistive head. The magneto-resistive head generates a response signal to transmit digital information read from a magnetic media storage device. The asymmetry is corrected in a negative feedback manner by squaring an output signal, modulating the squared output signal, and subtracting the modulated squared output signal from the response signal to generate the output signal. The circuit employs a differential amplifier as an input stage and a Gilbert multiplier circuit to square the output signal.

Abstract: A write driver in an H configuration for magnetic inductive write heads characterized by having both arms in the bottom half of the driver conduct current all the time, with only the top devices being switched. In this configuration there is no need to synchronize the switching of the top and bottom halves of the H-driver. Furthermore, the device half being switched can be optimized for speed independent of the properties of the other H-driver half.

Abstract: A method and apparatus for improving baseline recovery of an MR head using a programmable AC coupling pole. The location of the pole may be adjusted to achieve the fastest recovery from a baseline shift without degrading the normal channel performance. Further, the pole may be moved during the data recovery procedure to recover from a data read error. The programmable AC coupling pole includes a circuit path carrying digital data signals read from a recording media by a magnetic head, an amplifier coupled to the circuit path for amplifying the digital data signals, and a recovery time setting means having an programmable recovery time constant associated therewith. Once a data read error has been detected by the system, the recovery time constant may be adjusted to set a recovery time for the amplifier to provide readable data signals.

Abstract: A record/reproduction controlling signal generator with an error preventing circuit having an automatic level control circuit. The generator of the present invention is provided in a simple hardware form and is adapted to synchronize to a recording point in such a manner as to preclude transient phenomena that may occur when the power is first turned on to the device.

Abstract: A power-reduced digital control within a feedback control loop of a sampling data detection channel controls a predetermined operating parameter of the channel in which an analog to digital converter provides digital samples of information in the channel at a predetermined channel clock rate. The digital control comprises a parameter error extraction circuit clocked at the predetermined channel rate which is connected to receive digital samples from the analog to digital converter, and which extracts parameter error values from the digital samples; an averaging circuit for averaging the extracted parameter error values over an integral submultiple of the predetermined channel clock rate; and a parameter error processing circuit which is connected to the parameter error extraction circuit and clocked at the integral submultiple of the predetermined channel rate for generating and putting out digital control values within the feedback control loop for controlling the predetermined operating parameter.

Abstract: A read channel (18) for use in a mass storage system is provided. The read channel (18) includes a plurality of circuit modules circuit and an error estimation circuit (50). The plurality of circuit modules may include circuitry such as a VGA (40), an LPF (42), and an equalizer (48), for conditioning an analog data signal. The plurality of circuit modules receive the analog data signal from a disk/head assembly (12) and condition the signal to generate a digital data signal. The error estimation circuit (50) receives an analog signal from one of the plurality of circuit modules, such as the equalizer (48), and analyzes the analog signal to generate an analog error output signal (94) that is used in the read channel (18) and provided to external circuitry.

Abstract: In a magnetic recording drive having a plurality of magnetic heads each employing a magnetoresistive sensor for the purpose of averaging the time required for sense currents to be caused to flow through the respective magnetoresistive sensors to shorten the longest reproducing time and to suppress the degradation of the characteristics due to the electromigration, thereby improving the reliability of the magnetic recording drive, the magnetic recording drive includes circuits for averaging the useful life depending on the currents caused to flow through the respective magnetoresistive sensors among the plurality of magnetic heads, whereby the time required for the sense current to be caused to flow through one MR reproducing head is greatly shortened. Therefore, the levels of outputs of the MR reproducing heads can be increased without reduction of the reliability and thus the reliability of the magnetic recording drive can be improved.

Abstract: A circuit and method for detecting write-safe conditions for a magnetic storage device The circuit includes an electrical interconnect, a write-safe circuit, a write-driver circuit, a read amplifier and a read/write element. The electrical interconnect has a write path and a read path. A read element is coupled to one end of the read path, while the read amplifier is coupled to the other end of the read path. A write element is coupled to an end of the write path that is in proximity to the read element, while a write-output circuit is coupled to the other end of the write path. Preferably, the write element and the read element are part of a magneto-resistive head, such as a Piggyback-Magneto-Resistive head. The write-safe circuit, coupled to the read amplifier, detects a write-safe condition based on a signal induced into the read path by a write signal on the write path.

Abstract: A preamplifier bias circuit for use in an AC coupled magnetoresistive read head amplifier which includes a pair of head contacts, a pair of amplifier inputs, a pair of coupling capacitors and a means for selectively shunting the amplifier inputs and rapidly charge the coupling capacitors. The pair of head contacts and the pair of amplifier inputs couple the preamplifier bias circuit to a magnetoresistive element and a read amplifier, respectively. Each of the coupling capacitors is connected between one of the head contacts and one of the amplifier inputs to block a static potential across the magnetoresistive element. The means for selectively shunting the amplifier inputs selectively provides a low impedance path to rapidly charge the coupling capacitors and clamps the amplifier inputs to a known potential. By selectively providing a low impedance path, the AC coupled magnetoresistive read head amplifier can be protected and its associated delay time prior to operation can be decreased.

Abstract: The present invention is a method and apparatus for positioning a dual element magnetoresistive (MR) head relative to a storage medium in a storage device. The MR head has first and second MR elements. The storage medium is mounted in the storage device to allow relative movement between the MR head and the storage medium. The storage medium includes servo information provided to induce first and second thermal responses in the MR elements. A controller is coupled to the MR head and controls the relative movement between the MR head and the storage medium using the first and second thermal responses in the MR elements.

Abstract: Adaptive channel optimization in a disk drive is achieved by selecting a track of the recording medium and then writing a first data pattern to opposite sides of the selected track. The first data pattern is written a certain percentage off-track in relation to the centerline of the selected track. A second data pattern is then written directly on the selected data track and the off-track margin is determined as a function of how far the recording head can be positioned away from the center of the selected track during reading of the second data pattern while meeting a specified error rate. The off-track margin test is repeated iteratively using a combination of channel variable settings in order to find a set of variable settings which provides an optimal performance criteria for the drive.

Abstract: An apparatus and method for suppressing the effects of thermal asperities in readback signals of a hard disc drive are disclosed. A suppression circuit is provided having a clamping path that establishes an electrical short between a readback signal path transmitting the readback signal and a reference line for the readback signal in order to remove substantially all of the energy associated with the thermal asperity from the readback signal. The suppression circuit further includes a compensation path operably coupled between the readback signal path and the reference line to subsequently provide baseline compensation for the readback signal by introducing a non-zero impedance between the readback signal path and the reference line.

Abstract: An AGC circuit is used for read channels of a disk storage apparatus, by controlling a level of a reading output of a head to be kept constant. This AGC circuit has a gain control amplifier and a feedback circuit for digitally feeding back an output thereof. A maximum current value of a current type D/A converter is varied for every zone in zone bit recording. A gain adjusting time of the AGC circuit can be therefore minimized in each zone. A GAP length in the respective zones can be thereby reduced, and a storage capacity is increased. A maximum current value of the current type D/A converter is varied in a read/write area and a data surface servo area on a disk storage medium. It is therefore feasible to minimize the gain adjusting time of the AGC circuit in each of the servo area and the read/write area. The current type D/A converter is set so that a plus-side maximum current value is different from a minus-side maximum current value.

Abstract: A MR head amplifier of the present invention prevents a base potential of a transistor which supplies a current to a MR element from changing in a moment when the MR element changes from a write-state to a read-state. The MR head amplifier includes a loop amplifier that has a non-inverted input terminal connected to one end of a first transistor which supplies a current to a MR element and an inverted input terminal connected to one end of a second transistor which is supplied with a constant current through a constant current source. An output terminal of the loop amplifier is feedback to a base terminal of the first transistor via a first switch and one end of a capacitor whose other end is connected to a ground is connected to an output terminal of the first switch. The loop amplifier includes a second switch connected between the output terminal of the first switch and the base terminal of the first transistor, the second switch being closed during read-state and opened during write-state.

Abstract: A read/write data interface (26) is provided that interfaces with a read/write head (28) and is positioned in close proximity to the read/write head (28). The read/write data interface (26) includes a pre-amplifier (46) and a read channel (44). The pre-amplifier (46) amplifies an analog read signal and generates an amplified analog read signal in response. The read channel (44) receives the amplified analog read signal and generates a digital read signal in response.

Abstract: A signal reproducing circuit includes a magneto-resistive effect head having one end thereof coupled to a first power supply line, for reproducing data recorded on a magnetic recording medium in a read operation. A first constant current source is coupled between another end of the head and a second power supply line, for supplying the head with a sense current in the read operation. First and second transistors have collectors thereof coupled to the first power supply line, and are responsive to voltage signals obtained from both ends of the head, respectively. Second and third constant current sources are coupled between each emitter of the first and second transistors and the second power supply line, respectively, for supplying the first and second transistors with a predetermined constant current in the read operation. A capacitor is connected between each emitter of the first and second transistors.

Abstract: A method and apparatus adaptively controls the bias supply source for magnetoresistive (MR) read heads within a Direct Access Storage Device (DASD) to provide an optimized bias level for the ambient temperature. An optimal bias level for a given ambient temperature is provided in real time by sensing a temperature within a thermal path to the head (e.g., the ambient temperature surrounding the head) and adjusting the bias supply level to the maximum allowable level for that temperature. This adjustable bias level will thereby enhance MR transducer head sensitivity, improve the signal-to-noise ratio, and also reduce errors in reading data from magnetic storage media within the DASD. The maximum allowable bias supply source level is controlled so as to preserve the overall life expectancy of the MR heads.

Abstract: In a magnetic disk apparatus such as a floppy disk drive, the operating conditions can be readily and securely switched in a detailed manner using a simple construction. A magnetic head 20 is driven or a reproduced signal is converted into reproduction data by switching operating conditions in accordance with operating information stored in a memory circuit 30 where the operating information is set in the memory circuit 30 through external equipment.

Abstract: A sampled amplitude read channel is disclosed for reading data recorded on a disk storage medium by detecting an estimated binary sequence from a sequence of discrete-time sample values generated by sampling pulses in an analog read signal from a read head positioned over the disk storage medium. The read channel comprises a variable gain amplifier for adjusting the magnitude of the analog read signal before sampling, and a discrete-time gain control loop for generating a gain control signal applied to the VGA in response to the discrete-time sample values. The discrete-time sample values may, or may not be, synchronized to a baud rate of the recorded data. For example, when reading the user data the discrete-time sample values are synchronous, and when reading a servo address mark (SAM) the sample values are asynchronous. As such, the discrete-time gain control loop of the present invention is programmable to operate in a synchronous or asynchronous mode.