The Doherty power amplifier

The Doherty power amplifier (DPA) is hereby presented and described starting from the basic idea up to more advanced and state-of-art results and guidelines. The DPA historical aspect is also covered, describing the timeline of its evolution. Moreover, the reasons related to why this architecture, roughly 80 years after its invention, is still on its wave to realizing very advanced power amplifier stages for wireless systems, are also highlighted. The limitations of the original topology are put into evidence together with the proposed solutions to overcome them. Another significant part of this contribution is focused on the integration of the DPA architecture with high-efficiency power amplifier classes such as class F, Inverse F, and Inverse E. Some solutions to improve the output power back-off of the DPA such as multiway, multistage, and multistep are also reported. Finally, the DPA frequency response limitation is put into evidence and several enhanced solutions to improve it are presented. The theoretical aspects are supported with experimental solutions, implemented as Monolithic Microwave Integrated Circuit (MMIC), Microwave Integrated Circuit or simply Hybrid Integrated Circuit (HIC), highlighting the different approaches and behavior.