Here, we review the behavior of the Class-AB and Class-C amplifiers and then take a detailed look at how these two amplifier types can be combined to produce the Doherty amplifier, a system that preserves signal fidelity as well as boosts efficiency.

The fact that two inherently non-linear amplifiers can be combined to produce an amplifier with a linear response is an amazing result of Doherty’s 1936 invention. Despite its “antiquity”, the Doherty amplifier has become indispensable in today’s digital wireless revolution.

This article was originally published as the featured article in the August 2011 issue of the RF Globalnet Newsletter.