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
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page, please do.
Below are all of the forum threads, including all
the responses to the original posts.
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.