Jan,

Sure you can run class D at 27MHz... the problem is distortion. Class D
is very efficient but is really only meant for digital signals.

www.telstar-electronics.com


Jan Panteltje wrote:
On a sunny day (22 May 2006 04:45:06 -0700) it happened "Telstar Electronics"
wrote in
.com:

JSF... you're right about those "big amps". They are nothing but
hay-wired prototypes, mostly designed and constructed by persons having
no electronic background. I have looked at many of them over the years
and have found that they have major flaws such as inadequate cooling,
improper tuning, and instabilities/oscillations caused by improper
layout and long wires running around all over inside. Because of these
issues, their owners must keep a steady stream of expensive output
transistors flowing through them... if you know what I mean... LOL

www.telstar-electronics.com

Hi, I am reading on your website
http://www.telstar-electronics.com/S...Amplifiers.htm
about efficiency and conductingangle.
My question, has anyone ever attemped a class D (pulse width) modulated amp
with MOSFETS for 27Mc?

The limit would be the switching time, say if we have 1nS switching FETS,
and 37 nS period time, we use a bridge, so per 37 nS we switch 4x = 4nS

We dissipate any power (not counting Rds-on losses), could we achieve 80%
efficiency?
There are also losses from transformer and Pi filter of course.
And perhaps you would need a switchmode to get a higher operating voltage,
mmm that would bring it down to .8 x .8 = 64 % + filter and other losses....
But it COULD take you into the kW range with cheap FETS?

Whatdoyouthink? ;-)