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Infrared LED Thermal Droop Compensator

IP.com Disclosure Number: IPCOM000040114D
Original Publication Date: 1987-Sep-01
Included in the Prior Art Database: 2005-Feb-01

Publishing Venue

IBM

Related People

Authors:
Bustamante, CM Zalph, WN [+details]

Abstract

A technique is described whereby an electrical circuit is added to infrared light-emitting diode (LED) transmitting circuitry so as to compensate for thermal droop. Thermal droop is the loss of infrared transmitting capability of LEDs as the diode temperature rises with use. The circuit compensates for the thermal droop by controlling the current applied to the LED, thereby increasing the performance of communication packets. (Image Omitted) Since all LEDs exhibit a decrease in emitted infrared light as the diode temperature increases, bit error rates (BERs) of transmitted data also increase as the diodes heat up, placing a limit on usable packet lengths. Typical optical output power loss is approximately 1% per oC. As data is transmitted, the temperature of the LEDs will increase, reducing the light output for transmission.