Filter control circuit
CA 2016408 C · Owner: Bell-Northern Research Ltd. · Inventors: Brown, Anthony Kevin Dale
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
Abstract of the Disclosure A filter control circuit uses a compound FET as a resistance element. The compound FET includes parallel FETs having different gate widths to provide different drain-source resistance characteristics, which overlap to provide an extended operating region, that approaches a linear curve for the combined resistance characteristic. The control voltage used to control the compound FET may be coupled to like compound FETs in the filter being controlled. - i -
Read the whole patent
Listed from its CIPO record in Patent Yard's archive of Canadian patents past their term. Its claims, description and drawings are in the CIPO record and on Google Patents, and the Claude kit works from them.
Why it's free to use
- Filed May 9, 1990 and granted August 17, 1993. A Canadian patent filed from October 1, 1989 lasts 20 years from filing, so its term ended May 9, 2010.
- A certificate of supplementary protection adds at most two years for a drug, so even that would have ended by May 9, 2012.
- We check Canadian rights only. A patent in its family in another country could still be in force: check its family on Google Patents.
Timeline
Timeline From CIPO dates
Sources & verification
Official CIPO records
Everything on this page comes from the CIPO record linked above. Contains information licensed under the Open Government Licence – Canada.