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:
Aug. 19, 2003
Filed:
Apr. 28, 2000
Adrian A. Battagin, Toronto, CA;
Leitch Technology International Inc., Toronto, CA;
Abstract
An automatic gain control circuit for an optical receiver couples the low level signal produced by an optical detector to a signal amplifier, preferably a double-ended differential amplifier with the optical detector output fed into the high input and the low input coupled to ground, the gain of which is controlled by a negative feedback circuit. The feedback circuit comprises a signal level detection circuit coupled to the amplifier output, such as high-speed Schottky diodes acting in conjunction with an operational amplifier. The Schottky diodes are coupled to ground through AC coupling capacitors, and oriented in opposite directions, so when the amplified signal exceeds a conduction threshold of the Schottky diodes the capacitors are respectively charged and drained, establishing a voltage difference between the input terminals of the operational amplifier. The resulting current output from the operational amplifier to reduce the voltage difference is also fed to the gain control pin of the signal amplifier, reducing its gain. The differential output signal is equalized for transmission to switching, routing or processing equipment or to an HDTV receiver.