Post subject: stability in Power amplifier Posted: Tue
Feb 27, 2007 9:56 am
Joined: Tue May
02, 2006 4:59 am
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.
Post subject: 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.
S parameters 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
Post subject: Posted: Mon Apr 09,
2007 9:37 pm
Joined: Tue Mar 15, 2005
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.