EMRFD Message Archive 6980

Message Date From Subject
6980 2011-12-09 04:26:31 Stephen Farthing Class D amplifiers...

Dan Tayloe presented a paper some years ago about Class E amplifiers,
either at Pacificon or FDIM. That, and the paper by Dave Gipe presented at
FDIM more recently are well worth reading if you want to get the most out
of experimenting with Class E. I am not sure if either of them are
subscribers here but the papers would make a worthwhile addition to the
Files section.

73s Steve G0XAR

It is vain to do with more that which can be done with less.....William of

NATO has deployed the ultimate weapon against the Taliban....Elmo and
Sesamie Street!

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6985 2011-12-09 09:34:19 jasonb1963 Re: Class D amplifiers...
Hi Steve,

I have a lot of literature on Class E amplifiers, including some written by Dan Tayloe. I've read through everything I can get my hands on and built numerous experimental amplifiers -- some of which are even on PC boards now.

As Dan points out in one of his papers, if you design a Class E amplifier for broadband use, you will probably not get more than around 60% efficiency out of it. Moreover, it will never truly be broadband because of the tuned circuits that exist on the output side of the transistor.

I also find the load angle limitation particularly annoying because many of the amplifiers I built are borderline on meeting FCC regulations on spurious emissions without additional filtering, and that is tricky to do when one needs to keep the load angle approximately constant in the bandwidth one wishes to operate in.

I guess I'm wondering why bother with Class E amplifiers at all since they seem inferior to the Class D configuration in almost every way.

By the way, I'm talking here about current mode Class D amplifiers, which have a square voltage waveform on the collector/drain, and a sinusoidal current waveform flowing out of the collector/drain.

I've seen others talk about the Class D amplifier as if it's nothing more than a Class C amplifier driven by a square wave and with a conduction angle less than 180 degrees. This is definitely not what I am talking about here and I don't even think that such an amplifier is really Class D at all based