The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Nov. 25, 2003
Filed:
Aug. 10, 2001
Samuel I. Green, St. Louis, MO (US);
The Boeing Company, Chicago, IL (US);
Abstract
A photodetector circuit having a power supply and an avalanche photodiode coupled electrically thereto. The power supply includes a first portion, which supplies a substantially constant current, and a second portion, which supplies a substantially constant voltage. At low to moderate optical input signal levels, the substantially constant current that is applied to the avalanche photodiode generates a biasing potential that provides a signal gain, the magnitude of which varies depending upon the optical input signal level. A bias filter between the power supply and the avalanche photodiode slows changes in bias voltage so that the instantaneous photocurrent follows the modulation on the input optical signal. With constant average current bias, the bias potential automatically adjusts with temperature and sample variations to give the same average current flow. The optimum bias current is set depending on the type of avalanche photodiode and the bandwidth and noise characteristics of the following preamplifier.