Technology comparison and considerations for handset power amplifiers

Average power power tracking (APT) and envelope tracking (ET) power amplifiers require high efficiency across a range of supply voltages, which is a change from old fixed voltage systems. The performance of these amplifiers is usually characterized by a so-called “waterfall curve”[1-3]. While circuit design choices can certainly be a factor in this roll-off of PAE with decreasing supply voltage, it is also necessary to evaluate device technologies to understand the trade-offs and opportunities they present for these applications. For technology development, it is advantageous to see if “simpler” measurements, such as RF-Knee[4] correlate to these waterfall measurements since they are easier to collect. In this paper, the considerations for device performance for these applications will be presented and discussed.