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
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Parasitic oscillations - 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: Parasitic oscillations Posted: Tue Jul 26, 2005
Could someone suggest a couple of good references
on low frequency parasitic oscillations in microwave amplifiers?
Post subject: Posted: Tue Jul 26, 2005 7:58
Joined: Mon Jun 27, 2005 2:02 pm
Please try the following:
http://www.semiconductors.philips.com/a ... /LNA97.pdf
Post subject: ThnxPosted: Tue Jul 26, 2005
Thank you very much for the reference. I will
have a re-look at the biasing circuitry and the bypass capacitors in
my circuit. From a practical standpoint, how would one determine (when
testing the amplifier) if low frequency products were modulating the
Post subject: Posted:
Tue Jul 26, 2005 9:25 am
If you know the bandwidth
of your input modulated signal you can see if the voltage on various
points (Base, collector) on the amplifier's circuit has AC components
(With high-speed oscilloscope or with spectrum analyzer don't forget
to use DC block for this measurement) if you see these components at
these points, you can estimate by their magnitude if your bypassing
is adequate or not.
Alternatively, you can inject 2 input CW
signals with known offset between them and do this measurement.
Should you need more information, please let me know.