Abstract: A fly height controller circuit for a disk drive head having a resistive heater is disclosed. The fly height controller includes an error amplifier that controls a variable current source driving the resistive heater. The error amplifier compares a desired heater power signal with a feedback power signal that is generated by a multiplier. The multiplier receives a signal corresponding to the resistive heater current, for example as generated by a second variable current source also controlled by the error amplifier, and a signal corresponding to a voltage across the resistive heater. A first differential amplifier develops a differential voltage corresponding to the heater voltage. A second differential amplifier is biased by the resistive heater current signal, and receives the differential voltage form the first differential amplifier. A differential current generated by the second differential amplifier produces the feedback power signal as an output voltage.

Abstract: A pole and zero circuit for changing the position of a pole, or a zero, of an amplifier including a capacitor to change the position of the pole or zero for the amplifier, a first current path for the capacitor, a variable impedance device in the first current path to connect the capacitor to the amplifier, and a current source to control the impedance of the variable impedance device.

Abstract: A pole and zero circuit for changing the position of a pole, or a zero, of an amplifier including a capacitor to change the position of the pole or zero for the amplifier, a first current path for the capacitor, a variable impedance device in the first current path to connect the capacitor to the amplifier, and a current source to control the impedance of the variable impedance device.

Abstract: A programmable current source is provided for an H-switch to dampen overshoot resulting from a drop in voltage at a node during data transitions. The programmable current source is connected to both nodes of the H-switch on each side of the write head and is responsive to a voltage drop to below a threshold voltage at one node to injecting current into the one node during the period that the node voltage is below the threshold voltage. Preferably, a second programmable current source is connected to both nodes and is responsive to a voltage rise to above a second threshold voltage at the one of the nodes to sink current from the node to dampen undershoot.

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: A write driver, having a pair of head pins for connection to a write head, includes two push-pull buffer circuits connected respectively between first and second pull-up resistors and the control nodes of first and second upper drive transistors. The buffer circuits selectively charge and discharge the inherent capacitances of the upper drive transistors, thereby accelerating their turn on and turn off without diminishing head swing. Moreover, connecting the buffer circuits between the pull-up resistors and the upper transistors effectively isolates, or buffers, the pull-up resistors from the self-inductance voltages of the write head, reducing glitching in the write-head output signal.

Abstract: An open-loop biasing circuit for a magnetoresistive element provides high common mode and power supply rejection. Two current sources are connected together by two conduction paths. A first conduction path has two impedances. One impedance is tied between the first current source and ground and the second impedance is tied between the second current source and ground. The second conduction path includes the magnetoresistive element. A capacitive path between the two current sources reduces power supply noise and a voltage follower reduces parasitic capacitance in the capacitive path.

Abstract: A preamplifier and its associated biasing circuitry for connection to a magnetoresistive sensor having a first end and a second end is disclosed. The biasing circuitry properly biases the preamplifier such that the preamplifier can properly read signals from the sensor. The preamplifier includes a first transistor. A base of the first transistor is connected to the first end of the magnetoresistive sensor. An emitter of the second transistor is connected to the emitter of the first transistor. A collector of the third transistor is connected to the collector of the first transistor. A base of the fourth transistor is connected to the second end of the magnetoresistive sensor, while the collector of the fourth transistor is connected to the collector of the second transistor, and the emitter of the fourth transistor is connected to the emitter of the third transistor. The preamplifier further includes a voltage source and a first and a second resistor.

Abstract: An open-loop biasing circuit for a magnetoresistive element provides high common mode and power supply rejection. Two current sources are connected together by two conduction paths. A first conduction path has two impedances. One impedance is tied between the first current source and ground and the second impedance is tied between the second current source and ground. The second conduction path includes the magnetoresistive element. A capacitive path between the two current sources reduces power supply noise and a voltage follower reduces parasitic capacitance in the capacitive path.

Abstract: A first differential amplifier circuit is provided having a first and second input terminal suited for connection to a magnetic head. The first differential amplifier circuit includes first and second output terminals for providing a read output signal. A second differential amplifier circuit is provided which has first and second input terminals connected to the first and second input terminals, respectively, the first differential amplifier circuit. The second differential amplifier circuit also includes first and second output terminals. A first feedback capacitor is provided which is connected between the first input terminal of the first differential amplifier circuit and the first output terminal of the second differential amplifier circuit. A second feedback capacitor is provided which is connected between the second input terminal of the first differential amplifier circuit and the second output terminal of the second differential amplifier circuit.

Abstract: A direct AC-coupled amplifier for use with a plurality of magnetoresistive read elements includes a differential amplifier having first and second inputs and first and second outputs. A plurality of input circuits are provided, one for each MR element. Each input circuit has first and second connections to opposite sides of the respective MR element and a pair of emitter-follower its. Each emitter-follower circuit comprises a transistor having a base connected to one of the connections and a collector arranged to be connected a first voltage source. A capacitor is connected between the emitter of each of the transistors and a respective input of the amplifier. A current is applied to the first and second connections of a selected one of the input circuits to operate the respective MR element.

Abstract: The present invention discloses a write driver circuit for driving a magnetic head in an information storage system. The write driver circuit is connected to first and second voltage supply terminals and includes first and second data input terminals for receiving data input signals. The H-switch has a pair of pull-up transistors and a pair of pull-down transistors to switch current flow between a first direction and a second direction which is opposite to the first direction. A pair of anti-saturation circuits are connected to the H-switch to bias the pull-up transistors. The anti-saturation circuits contain a transistor having a collector, a base and an emitter and a pair of substantially similar diodes connected between the base and the collector of the transistor.

Abstract: The present invention is a read amplifier that is configured for interconnection with a magnetic head through head contacts. The read amplifier includes a differential transistor pair that is connected in a common emitter configuration. The bases of the differential transistor pair are connected across the magnetic head. A bias generator provides a bias current to the bases of the differential pair of transistors through first and second input resistors. The bias generator includes a circuit for providing a compensation voltage to the bases of the differential transistor pair that is based on changes in the bias current supplied to the differential transistor pair.

Abstract: A read preamplifier for use in reading data in a magnetic storage system uses positive feedback to reduce the preamplifier's input capacitance. The read preamplifier includes first and second voltage supply terminals. An input is coupled to the second voltage supply terminal and receives input signals from a connected magnetic head. An output is coupled to the first voltage supply terminal and to the input for producing output signals based upon the input signals. A positive feedback circuit, coupled to the input reduces the input capacitance of the read preamplifier.

Abstract: The present invention is an improved current mirror circuit. This improved current mirror circuit includes first and second transistors of the same conductivity type and have bases connected together. The first transistor is connected between a first supply terminal and an input terminal. The second transistor is connected between a first supply terminal and an output terminal. Included is a feedback circuit for providing a voltage feedback between the input terminal and the bases of the first and second transistors. Also included is a bias circuit for providing a bias current to the feedback circuit that is based on the input current.

Abstract: A magnetic head swing clamp configured for interconnection with a read/write preamplifier of the type including a read differential transistor pair connected to an inductive head. The collectors of the transistors in the read differential transistor pair provide first and second read output signals at first and second read output terminals for connection to a read amplifier. The magnetic head swing clamp comprises a reference voltage generator which produces first and second reference voltage levels at first and second reference voltage output terminals. Positive and negative voltage clamps are electrically connected to the first and second reference voltage output terminals, respectively, and to the first and second read output terminals. The positive and negative voltage clamps clamp voltage swings in the first and second read output signals as functions of the first and second reference voltage levels.

Abstract: An amplifier includes first and second transistors each of which has a conduction path, with first and second conduction path terminals, and a control terminal for controlling conduction through the conduction path. The amplifier also includes a current source and voltage reference terminal for being coupled to a voltage reference. A first Schottky diode has an intrinsic series resistance and is coupled between the second conduction path terminal of the first transistor and the current source. A second Schottky diode has an intrinsic series resistance and is coupled between the second conduction path terminal of the second transistor and the current source.

Abstract: An open head detection circuit for detecting an open-circuit condition in a magnetic head connected to head contacts. The detector circuit includes a threshold source which generates a threshold voltage that is between a head contact voltage representative of a connected head and a head contact voltage representative of an open head. A comparator, coupled to receive head voltage signals from the head contacts and coupled to the threshold source, compares the head voltage signals to the threshold voltage and generates comparator signals representative of the comparison. Sampling circuitry, coupled to the comparator and coupled to receive write data signals, samples the comparator signals after detection of the write data signals and before the write data signals affect the comparator signals.