[Amps] Low pass filters and saturated operation

[Steve Thompson]

Manfred,

Your amplifier reminds me of something I worked on in the 80s, 
trying to improve efficiency in military manpack transmitters. One 
approach which was promising came out of an article:

F. H. Raab, “The class BD high-efficiency RF power amplifier”, 
IEEE Journal of Solid-State Circuits, vol. SC-12, no. 3, June 1977

I can't find a full version online to link to; I'm sure I still 
have a paper copy somewhere which I'll scan if/when I find it.

Steve

>     coughdiplexer
> 
> No go! While it's true that a diplexer would nicely terminate all harmonics and thus avoid impedance transformation in the line, it would also negate the main advantage of an ET transmitter, which is the high efficiency. With a near square wave voltage at the drains, a diplexer would dissipate a considerable amount of power in the load resistor.
> 
> 
> The game is making an amplifier that does not dissipate power generated at harmonic frequencies, but that simply doesn't generate any power there. To that end the low-pass filter cannot be a diplexer.
>