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...
All trademarks, copyrights, patents, and other rights of ownership to images
and text used on the RF Cafe website are hereby acknowledged.
My Hobby Website:
stability in Power amplifier - 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: stability in Power amplifier Posted: Tue Feb
27, 2007 9:56 am
Joined: Tue May 02, 2006
How can I simulate and calculate
stability in power amplifier ?
In small signal i can use the s-parameters
for that (K>1 and |delta|>0) but in power amplifier the s-parameter
is not available because its define only for small siganl.
Power amplifiers and S-ParametersPosted: Wed Feb 28, 2007 3:46 am
Joined: Wed Feb 22, 2006 3:51 pm
Let's phrase your objection more precisely:
do not provide s-parameter data for their transistors when used in anything
other than Class A amplifiers.
Large signal amplifiers certainly
reflect power. Measure the magnitude and the angle of the reflection,
and you can calculate an s-parameter.
vary unpredictably when a transistor is driven into nonlinear operation.
By "unpredictably" I mean that they depend on parameters that vary from
device to device, and which aren't usually measured or listed at all.
There are entire books written on the subject - Cripps has written
two good ones (check www.artechhouse.com).
Post subject: Posted: Mon Apr 09,
2007 9:37 pm
Joined: Tue Mar 15, 2005 11:43
I agree with
S-parameters are not limited to small-signal. Let's put
it this way, S-parameters are basically port-to-port measurement, it
can be small-signal and large-signal. It depends on the measurement
According to experience, stability can be
defined well by small-signal, by defining K and delta. Most of cases,
it wont change too much in large-signal. Unless, there are some "unwanted"
positive feedback happens or driven transistor to extreme bias point.
I hope it helps.