Hewlett-Packard Company

Robert A Zimmer

Charles E Moore

Travis N Blalock

Rajeev Badyal

Richard A Baumgartner

Larry S Metz

Ran-Fun Chiu

Sui-hing Leung

Li Ching Tsai

Thomas M Walley

Richard A Baugh

James S Ignowski

Kenneth R Stafford

An analog, fully integrated, partial response maximum likelihood (PRML) read channel utilizing a high-performance analog delay line, an analog adaptive equalizer and an analog Viterbi detector is provided, resulting in saved space, performance gains, and lower power consumption. For signal detection and reconstruction used in read operations, the partial response maximum likelihood (PRML) read channel includes a variable gain amplifier coupled to a lowpass filter for input to an adaptive analog equalizer. The adaptive analog equalizer comprises an analog delay line and an analog feedforward equalizer (FFE). An analog Viterbi detector employs maximum-likelihood sequence estimation (MLSE) techniques to performs the signal detection function. A decoder/descrambler produces a final reconstructed signal. The analog implementation of a partial response maximum likelihood (PRML) read channel also includes a scrambler/encoder coupled to a write precompensation circuit for output to a separate write head.

Analog implementation of a partial response maximum likelihood (PRML)

A circuit provides a high impedance input to an operational amplifier by substituting a p-channel field effect transistor for the bias resistor normally used on the input to an operation amplifier. By placing a PFET in place of the bias resistor, a resistance value can be created that is hundreds of times higher, for the same area of silicon within the integrated circuit, as that created with an actual resistor. This PFET has parasitic capacitance which may be significantly offset by connecting the gate of the PFET to the output of a source follower circuit having its input connected to the inverting input of the operational amplifier. The circuit may be still further improved by using a voltage follower amplifier circuit in place of the source follower.

High impedance circuit using PFET

A nonlinear noninverting amplifier design for receiving and amplifying an input signal in an optical communication scheme having a nonlinear inverting feedback is disclosed. The inverting feedback varies nonlinearly with the input signal to avoid saturation of the amplifier while providing a zero state input amplitude signal to reduce the amplitude of the input signal required to turn-on the feedback, thus allowing the amplifier to operate with a wide variation of optical generators, paths, and converters. A nonlinear noninverting amplifier design is provided which eliminates the need for automatic gain control circuitry and can be designed as an integrated circuit.

Nonlinear noninverting transimpedance amplifier

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Loveland, CO, United States of America

Robert A Zimmer