Vtc Inc.

Texas Instruments Corporation

Agere Systems Guardian Corp.

Vtc Bipolar Corporation

Craig Matthew Brannon

Tuan V Ngo

John J Price, Jr

Douglas Warren Dean

Jeremy Robert Kuehlwein

Raymond E Barnett

Indumini W Ranmuthu

Raymond Elijah Barnett

Douglas R Peterson

Siang Tong Tan

Jeremy R Kuehlwein

John A Schuler

Pete J Jung

Doug R Peterson

A damping circuit having an input terminal and an output terminal is described. The damping circuit comprises a driver having an input and an output; an RC circuit coupled between the input terminal and the output; and a resistor coupled between the output and the output terminal, wherein the RC circuit delays passing a signal from the output terminal to the input terminal and a low impedance associated with the driver generally reduces ringing.

Laser diode driver damping circuit

A circuit for providing a write current having a programmably adjustable duty cycle in a hard disk drive write channel has a differential pair gain circuit for receiving a data input signal and generating a differential output voltage to provide a differential write signal for generating the write current. First and second programmable current sources are connected to the differential pair gain circuit to create a programmable voltage offset of the differential output voltage to programmably adjust the duty cycle of the write current.

Technique for duty cycle shift in hard disk drive write system

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.

Disk drive fly height control based on constant power dissipation in read/write head heaters

An apparatus for use with a sensor includes first and second signal treating circuit segments coupled with the sensor for presenting a substantially balanced differential signaling representation of output signals from the sensor. Each respective signal treating circuit segment comprises a plurality of circuit elements having different electrical symmetries coupled in parallel and establishing a plurality of parallel signal paths having asymmetric signal handling characteristics. A feedback circuit is coupled with the first and second signal treating circuit segments and provides feedback signals to selected circuit elements in each of the first and second signal treating circuit segments. The feedback signals effect substantially balanced signal handling among the selected circuit elements having similar electrical symmetries.

Amplifier apparatus for use with a sensor

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.

Method for implementing high frequency programmable poles and zeros in disk drive preamplifiers

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.

Programmable damping for write circuits

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.

Referenced magnetoresistives sensor band pass preamplifier

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.

Write driver with buffer circuits between pull-up resistors and upper

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.

Open-loop MR biasing circuit with high power supply and common mode

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. The first resistor is connected between the voltage source and the collector of the first and third transistors, while the second transistor is connected between the voltage source and the collectors of the second and fourth transistors. Finally, a first current source is connected between the emitters of the first and second transistors and ground, while a second current source is connected between the emitters of the third and fourth transistors and ground.

Pseudo differential voltage sense MR preamplifier with improved bandwidth

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.

Amplifier having a differential input capacitance cancellation circuit

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.

Growing community of inventors

Maplewood, MN, United States of America

Craig Matthew Brannon