Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would
be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate
that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views.
It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if
you would like to post something on RF Cafe's
page, please do.
Below are all of the forum threads, including all
the responses to the original posts.
Post subject: PA emitter area Posted: Fri Nov 18, 2005 7:52 pm
The issue for power output is
current density in the emitter-base junction - you can't increase that without limit. So the more area, the more
power, given a limit on current density.
What determines Ft is (among other things) the width of the base
junction. Since junctions are usually the result of diffusion, smaller emitters often result in narrower base
Nf, on the other hand, is largely due to the resistivity in the base region.