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https://designers-guide.org/forum/YaBB.pl Design >> RF Design >> transconductance measurement https://designers-guide.org/forum/YaBB.pl?num=1166164372 Message started by sivacha on Dec 14th, 2006, 10:32pm |
Title: transconductance measurement Post by sivacha on Dec 14th, 2006, 10:32pm Hi, For my Gilbert mixer, how can i measure its transconductance(Gm)?? Theoritically it is (2/pi)*gm, gm being the transconductance of the RF transistor. Which analysis i can use to measure the Gm?? Thanks, Siva. |
Title: Re: transconductance measurement Post by ACWWong on Dec 15th, 2006, 2:37am You can measure the gm of you input transconductance stage. Typically for a Gilbert this is a source-coupled-pair or emitter-coupled pair. The gm reported by the DC operating point is usually a good start. For hand calculations you look at something like Gray and Meyer. If your Gilbert transconducatnce stage uses local series feedback (i.e degeneration) then the gm becomes gm/(1+gm*Zdeg). Again this is covered in Gray & Meyer and other standard analog IC design texts. Anyway irrespective of linearity technique/input toplogy, I often just DC sweep the output differential drain current versus input differential volatge. The derivative of the current with respect to the input voltage gives gm. Its a quick look see and is often sufficient if devices are operating upto a tenth of ft. |
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