GaN devices for communication applications: Evolution of amplifier architectures

This paper presents the design and implementation of power amplifiers using high-power gallium nitride (GaN) high electronic mobility transistor (HEMT) powerbars and monolithic microwave integrated circuits (MMICs). The first amplifier is a class AB implementation for worldwide interoperability for microwave access (WiMAX) applications with emphasis on a low temperature cofired ceramics (LTCC) packaging solution. The second amplifier is a class S power amplifier using a high power GaN HEMT MMIC. For a 450 MHz continuous wave (CW) signal, the measured output power is 5.8 W and drain efficiency is 18.5%. Based on time domain simulations, loss mechanisms are identified and optimization steps are discussed.