Stephen C Wilkinson-Gruber

US Patent:

6735731, May 11, 2004

Filed:

Mar 9, 2001

Appl. No.:

09/803077

Inventors:

John F. Ewen - Rochester MN
David W. Siljenberg - Byron MN
Stephen C. Wilkinson-Gruber - Rochester MN

Assignee:

International Business Machines Corporation - Armonk NY

International Classification:

G01R 3128

US Classification:

714733

Abstract:

Method and apparatus for testing a parallel optical transceiver are provided. One embodiment provides a built-in self-testing (BIST) parallel optical transceiver comprising a full-rate clock test pattern generator and a clock divider circuit connected to provide a half-rate clock signal to one of the one or more transmitter channels, and an error detector comprising one or more error detection circuits connected to one or more receiver channels and configured to receive the half-rate clock signal. Another embodiment provides a method for testing a parallel optical transceiver, comprising: generating a full-rate clock test pattern to one or more transmitter channels; providing a half-rate clock signal to one of the one or more transmitter channels utilizing a clock divider circuit; transmitting test pattern and half-rate clock signals to one or more corresponding receiver channels; and detecting error utilizing one or more error detection circuits connected to receive the half-rate clock signal.

US Patent:

62976850, Oct 2, 2001

Filed:

Jun 14, 2000

Appl. No.:

9/593997

Inventors:

John Farley Ewen - Rochester MN
Stephen Charles Wilkinson-Gruber - Rochester MN

Assignee:

International Business Machines Corporation - Armonk NY

International Classification:

H03K 342

US Classification:

327513

Abstract:

An output buffer provides a stable, predetermined low voltage differential over power supply, temperature, and process variations yet has a high speed of operation. More particularly, a data path of an output buffer includes an emitter-coupled differential amplifier followed by an output section of two level-shifting emitter followers. A predetermined operating current biases the differential amplifier for unsaturated operation and a reference current biases the output section for unsaturated operation. The data path remains unencumbered by compensation circuitry to preserve high speed operation. Instead, a voltage compensator biases the differential amplifier to compensate, at least in part, for variations in a supply voltage. In addition, a variable biasing current to the voltage compensator with a predetermined temperature coefficient may further temperature compensate the differential amplifier. In addition to such "upstream" compensation, the output buffer may further include "downstream" temperature compensation by the addition of a V. sub.