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The Doherty Amplifier: Past, present & future

Doherty Power Amplifier (DPA) is an old and fashionable configuration, introduced by W.E. Doherty in 1936 at the Bell Telephone Laboratories (BTL) of Whippany, New Jersey, for the realization of vacuum tube high-efficiency amplifiers. The original configuration has been successfully resurrected in the last decade. Actually, the proposed solution has become a hot research topic, representing the most suitable approach for implementing high efficiency transmitters, as the many published state-of-the-art results demonstrate. In this contribution, the evolution of the DPA from its original idea is presented, with the aim to stress its pros and cons. Starting from its original topology, the intrinsic limitations are reviewed together with new proposed solutions to overcome them, both in terms of architecture features and frequency limitations. Moreover, the theoretical aspects and the developed design methodologies are supported through experimental results, from MMIC or HIC realizations, highlighting different approaches and behaviors.