Gallium-Nitride (GaN) High-electron-mobility transistors (HEMTs) technology developments has been a breakthrough for microwave power circuits performances (e.g. power amplifiers) and is now widely accepted has a key-enabling-technology (KET) for future high-performance broadband RF/mmW integrated systems in 5G and future 6G front-ends. GaN HEMT device’s figures of merit like, e.g. high power density (high operating voltage, high current capabilities), good microwave performances, make it very suitable for RF functions integration, and many GaN functions have been demonstrated (power amplifiers HPA-MPA , low noise amplifier, RF control equipements).
However, compared with the previous competing technology Gallium-Arsenide (GaAs), GaN power devices have almost the same efficiency but offer 3X-5X more output power density, and thus thermal considerations are becoming of paramount importance. The mastery of peak and average energy efficiency and associated dissipated power at the device/circuit and module level imposes careful management of time domain voltage/current waveforms. High efficiency power amplifier structure like e.g. Doherty power amplifier are employed to improve average efficiency when modulated signal are being transmitted.
First , this talk reviews the GaN HEMT power cell and related circuit-level figures of merit for microwave power applications. Then it proposes a comprehensive analysis of high efficiency classes of operation of microwave transistor with emphasis on waveform engineering process. The second part concerns power amplifier architectures dedicated to the amplification of high peak-to-average power ratio (PAR) modulated signals. A particular focus is made on the Doherty power amplifier as it is the most commonly used topology in telecom infrastructure applications.