High-Efficiency Doherty Power Amplifiers

Chapter 10 describes the historical aspect of the Doherty approach to the power amplifier design and modern trends in Doherty amplifier design techniques using multistage and asymmetric multi-way architectures. To increase efficiency over the power-backoff range, the switchmode Class-E, conventional Class-F, or inverse Class-F operation mode by controlling the second and third harmonics can be used in the load network. The Doherty amplifier with a series connected load, inverted, balanced, push–pull, and dual Doherty architectures are also described and discussed. Finally, examples of the lumped Doherty amplifier implemented in monolithic microwave integrated circuits, digitally driven Doherty technique, and broadband capability of the two-stage Doherty amplifier are given.