'Bridging the gap between device and circuit characterization in RF power amplifiers'

RF power amplifiers based on GaN transistors are mainly degraded by thermal and trapping phenomena. Starting from low-frequency I/V measurements of two comparable GaN-on-SiC transistors (Qorvo vs. Wolfspeed), performance degradation of a RF power amplifier is evaluated for different classes of operation, i.e., class-A to class-E. The double pulse technique typically used in IV measurements is then applied at PA level to quantify the backoff gain reduction that can be associated with knee-walkout and current collapse in the transistor. By leveraging on this double-pulse characterization, trap release time constants are extracted and used to improve digital pre-distortion (DPD) linearization in the backoff region. Finally, a low-complexity behavioural model capable to estimate the transistor channel temperature is presented.