Copyright: 1996 - 2024
BSEE - KB3UON
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling
2 MB. Its primary purpose was to provide me with ready access to commonly needed
formulas and reference material while performing my work as an RF system and circuit
design engineer. The World Wide Web (Internet) was largely an unknown entity at
the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps
while tying up your telephone line, and a nice lady's voice announced "You've Got
Mail" when a new message arrived...
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My Hobby Website:
Negative Resistance - RF Cafe Forums
RF Cafe Forums closed its virtual doors in 2012 mainly due to other social media
platforms dominating public commenting venues. RF Cafe Forums began sometime around
August of 2003 and was quite well-attended for many years. By 2010, Facebook and
Twitter were overwhelmingly dominating online personal interaction, and RF Cafe
Forums activity dropped off precipitously. If the folks at
phpBB would release a version with integrated
sign-in from the major social media platforms, I would resurrect the RF Cafe Forums,
but until then it is probably not worth the effort. Regardless, there are still
lots of great posts in the archive that ware worth looking at.
Below are the old forum threads, including responses to the original posts.
|-- Amateur Radio
Gripes & Humor
-- CAE, CAD, &
Test & Measurement
Post subject: Negative Resistance Posted: Sun Sep 16, 2007
Joined: Fri Aug 11, 2006 6:07 am
I'm trying to synthesize a negative resistance to add to a circuit.
As far as I know there are three popular ways of doing so:
a device with negative resistance characteristics (e.g. Tunnel Diode).
2. Using a configuration of OpAmps with feedback that gives a negative
resistance when seen from the input.
3. Using a configuration of
BJTs, ot FETs.
It is the third method that I'm interested in
since I'm working at a somewhat high frequency and I need to be able
to integrate the resulting circuit on an IC. I'm specifically interested
in making a negative resistance using MOSFETs. I did read a couple of
papers that talked about the subject but it was quite general, with
no reference to biasing or methods of tuning. While I was able to sucessfully
simulate a negative resistance using two MOSFETs, the resulting resistance
was quite large (tens of Mega Ohms) and it was unstable when put in
a larger circuit.
The resistance I need is S-type, in the range
of tens of Ohms. Can anyone point me to where I can get more info on