Investigation of class-B/J continuous modes in broadband GaN power amplifiers

The class-B/J mode continuum in power amplifiers (PAs) defined at the current source plane is discussed considering different parasitic elements including CDS as well as the package. Based on this realistic device description the change of the continuous load impedances depending on the reference plane is demonstrated. It is shown that the design flexibility predicted by the continuous mode theory decreases if the transistor package is taken into account. The presented investigations provide the basis for the design of a broadband GaN PA. In the frequency range of 0.9 GHz to 1.8 GHz, this PA achieves a saturated output power of more than 70 W with an efficiency η of 56–63 %. In the extended frequency band up to 2.3 GHz an output power of still 60 W with 53 % drain efficiency is available.