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:
Apr. 18, 2000
Filed:
Dec. 08, 1997
Samuel Alfred Tiller, Ottawa, CA;
John J Nisbet, Nepean, CA;
Nortel Networks Corporation, Montreal, CA;
Abstract
A linear gain controlled amplifier comprising a differential transistor pair having an input and an output. The input is connected to a current supply which includes both AC and DC components. A voltage is derived which is proportional to the DC current component and this is compared with a control signal to produce an error signal which is supplied to the gain control terminals of the differential transistor pair. Traditionally, gain control has been implemented using a closed loop consisting of a power detector, a loop filter and a gain control element. The output of the power detector is compared with a reference voltage in a comparator, the output of which is filtered by the loop filter and applied to a control input of the gain control element. Most power detectors are either inaccurate or expensive and elaborate and may exhibit a control error of several decibels. The gain control elements themselves typically have non-linear control characteristics and suffer from poor repeatability and temperature variations which can necessitate extensive calibration. The present invention substantially avoids the foregoing problems by avoiding use of the prior art power detector and gain control element.