Comparison of Technologies for APT and ET Applications

Average power tracking (APT) and envelope tracking (ET) power amplifiers require high efficiency across a range of supply voltages. 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. We demonstrate the correlation of simpler measurements to the waterfall measurements and also compare the performance of different HBT material designs and other technologies.