This application note will discuss fundamental usage methodologies to design with GaN HEMT devices. Specifically, this discussion will center on proper biasing techniques as well as temperature compensation surrounding GaN HEMT technology. A bias sequencing circuit and a temperature compensation circuit will be presented.

The biasing of high power RF devices, especially GaN devices, requires special attention. The concerns are mainly for preventing instabilities or oscillations, maintaining large drain current with a small voltage drop, and bias decoupling circuits to reduce interference with the RF matching circuit as well as limiting its influence on the linearity of the device. Also, properly maintaining the device current over temperature improves the performance in multiple operating environments. This application note will address the issues associated with biasing, bias sequencing and temperature compensation of a Nitronex GaN HEMT.