Vtc Inc.

Agere Systems Guardian Corp.

Douglas R Peterson

Tuan V Ngo

Craig Matthew Brannon

John S Shier

Peter J Jung

A preamplifier for an MR element having first and second ends includes first and second feedback loops controlling the biasing of the MR element. The first feedback loop responds to a center voltage of the MR element to control a current source coupled to the first end of the MR element, and the second feedback loop responds to an output voltage across the MR element to control a current sink coupled to the second end of the MR element. In one embodiment, the preamplifier includes a multiplexer coupled between first and second MR elements and the first and second feedback loops. The multiplexer electrically isolates the first and second MR elements to improve common-mode rejection and feedback performance of the preamplifier.

Current biasing voltage sensing preamplifier for magnetoresistive heads

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 preamplifier circuit, which produces an output signal representative of signals from a magnetoresistive read head, includes a current bias circuit for providing a bias current to the read head, and first and second amplifiers for amplifying signals from the read head. The first amplifier, with an input for coupling to the read head, outputs first signals representative of changes in head resistance. The first signals have an amplitude substantially independent of the head resistance and proportional to a temperature dependent characteristic of the first amplifier. The second amplifier, which is coupled to the first amplifier, outputs a second signal having an amplitude proportional to the amplitude of the first signals and inversely proportional to the temperature dependent characteristic. Thus, the amplitude of the second signal is substantially independent of head resistance and the temperature dependent characteristic.

MR head preamplifier with output signal amplitude which is independent

The present invention is a magnetoresistive element amplifier circuit for amplifying signals produced by a magnetoresistive element. The amplifier circuit includes a gain setting resistor and a first and second transistor. The first transistor has a pair of controlled terminals connected between first and second supply terminals and in series with the magnetoresistive element. The second transistor is connected to the first transistor in a cascode configuration. The second transistor has a pair of controlled terminals connected between the first and second supply terminals and in series with the gain setting resistor. The magnetoresistive element is in a separate DC current path from the gain setting resistor. The first and second transistors provide small signal current through the gain setting resistor for producing gain adjusted output signals.

Single-ended cascode amplifier for magnetoresistive sensors

A circuit for rapidly charging a capacitor for a transition between operating states is provided. A controlled reference voltage is provided to reference the circuit. A comparator compares signals at the comparator inputs and provides an output dependent upon the comparator input signals. The output of the comparator enables or disables a controlled current charging circuit. The current charging circuit rapidly charges the capacitor when enabled.

Preamplifier noise filtering circuit

A write driver for driving a transducer in a storage system. The write driver includes first and second supply terminals and a H-switch for switching current flow through the transducer between a first direction and a second direction, opposite to the first direction. The H-switch includes pull-up transistors and pull-down transistors connected across the transducer for switching current flow through the transducer. Each pull-up transistor and pull-down transistor has a control terminal for controlling current flow through the transistor. The write driver further includes data input terminals for receiving data signals. A bias circuit is connected between the control terminals of the pull-up and pull-down transistors and the data input terminals for switching the pull-up and pull-down transistors between conducting and non-conducting states as a function of the received data signals. Each pull-down transistor has a corresponding synchronizing transistor connected between the control terminal of the pull-down transistor and the second supply terminal, which pulls current away from the control terminal of the pull-down transistor when the pull-down transistor is switched to the non-conducting state.

Write driver with H-switch synchronizing transistors

A write circuit for driving a magnetic head in a magnetic storage system which greatly improves the voltage swing across the magnetic head. The write circuit includes data input for receiving data input signals, a predriver current source, a predriver circuit, and a write driver circuit. The predriver circuit is connected to the data input and has first and second predriver current paths. The predriver current paths are connected to a predriver current source. The predriver circuit directs current from the predriver current source through the first and second predriver current paths as a function of the data input signals. The write driver circuit has first and second write currents paths connected across the magnetic head. The first write current path directs current through the magnetic head in a first direction and the second write current path directs current through the magnetic head in a second direction, opposite to the first direction. The predriver circuit and the write driver circuit are connected together in a current mirror configuration to mirror the predriver current from the first and second predriver currents paths into the first and second write driver currents paths, respectively.

Growing community of inventors

Minnetonka, MN, United States of America

Douglas R Peterson