Try:

"Practical RF Power Design Techniques", Irving Gottlieb
ISBN 0-8306-4129-7

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"Claude Frantz" wrote in message
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Where can I find good information about the principle and the design of
linear power amplifier using semiconductors, up to the full legal
power limit ?

Is it only possible to use power splitter ? I have seen broadcast
transmitters in the power range of many hundred of kW's, having an
power efficiency of more than 90 %. Do they use power splitter or
another design ?