On 12/02/14 15:06, Manfred Mornhinweg wrote:
/* snip */
If you want to keep things simple, the easiest way to reduce IMD in
solid state amps is to give them lots of negative feedback. To do that,
you have to start with excess gain! 30 years ago that was somewhat hard
to do. But nowadays there are FETs that have huge power gain in the HF
range. Given that the typical ham needs an amp having just 12dB gain,
you can burn up the FET's excess gain via negative feedback, getting
improved linearity in a class AB amplifier. /* snip */
I agree with the need for feedback, but the operating mode with the
best overall efficiency which is suitable for all modulation modes
without switching is class "B" push pull operation. Wide band solid
state designs eliminates the only drawback to class "B" push pull
operation with tubes which is the (double) band switching and tuning.
Neutralization is a snap with cross neutralization and the maximum gain
will be available for a little degenerative feedback.
I have always considered class "AB" to be class "A" just without the
linearity.
--
Ron KA4INM - Youvan's corollary:
Every action results in unwanted side effects.
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