The Doherty power amplifier

The Doherty power amplifier (DPA) architecture, in various formats using different technologies, has been a very popular means of providing high conversion efficiencies from raw electrical power to sophisticated modulated RF and microwave signals ever since the requirements for very high power amplitude modulated (AM) radio transmitters in the mid-1930's. This paper covers not only the “original stories” of high power tube-based Doherty power amplifiers for those early AM transmitters, but also provides many examples of implementations employing a range of modern semiconductor transistor and circuit technologies covering a wide range of power levels, modulation schemes and carrier frequencies.