Cree application note describes large signal accuracy in RF power transistors

April 13, 2015 // By Jean-Pierre Joosting
Cree has released an application note describing the high accuracy of its large signal models for RF power transistors, which allow RF design engineers to reduce PA design iterations, design time, and development costs.

The company's GaN HEMT devices find applications in broadband amplifiers, cellular infrastructure, tactical and satellite communications, and test instrumentation due to their high efficiency, high gain, and relatively simple matching characteristics. However, it is notoriously difficult to predict the large signal performance of RF power devices like these, due to self-heating and the complex dependence of nonlinearity component parameters on signal level, thermal effects, and ambient conditions. Consequently, design engineers must either develop hardware and conduct time-consuming and potentially inaccurate load-pull measurements or rely on the accuracy of large signal models to evaluate such devices in their simulation environments.

To put designers at ease and spare them the time and cost of conducting load-pull measurements, as well as the risk of generating defective data, Cree carefully compared measured and modeled data for its 100 W and 200 W GaN-on-SiC high electron mobility transistors. Verified using a standard load pull system at optimal impedances over multiple frequencies, the results demonstrate the high accuracy with which the company’s proprietary large signal models represent actual device performance. Further, in addition to reducing design time and development costs related to load-pull measurements, these highly accurate models also allow engineers to conduct in-depth “what-if” analyses that can close layout links and enable faster design cycles and more first-pass design successes.