Challenges of power amplifier design for envelope tracking applications

In this paper, we present the challenges of modeling and characterization of power devices for use in the design of power amplifiers (PA) intended for use in envelope tracking (ET) applications. We will demonstrate our approach to obtaining the necessary design data from a 2x100 um GaN device. Characterization of power transistors generally occurs at a small range of drain voltage biases whereas in envelope tracking applications the PA must be able to perform well over the entire range of drain modulation that is fundamental to ETPAs. Here we used broadband s-parameter data as well as fundamental loadpull to characterize the device. We also discuss the requirements of the transistor models that are needed for successful PA design, including ET applications, highlighting the necessary features.