High-Efficiency VHF Class-Φ2 Power Amplifier with a GaN Sinusoidal Resonant Gate Driver

This paper presents a design methodology for high-efficiency VHF Class-Φ2 power amplifiers with a GaN-based sinusoidal resonant driver. While LDMOS devices are robust for the 10 - 20 W power level, their large input capacitance (Ciss) poses challenges for high-frequency switching. Conventional square-wave drive exhibits either excessive power consumption or circuit complexity, even hard to achieve zero voltage switching at higher VHF band. To overcome these limitations, a resonant driver using a GaN HEMT with low Ciss and its design methodology was proposed. This design employed an interstage matching network to reduce gate switching loss, minimize reflection, and enable efficient sinusoidal driving. Two 13 W PA prototypes were fabricated and compared: one using parallel logic gates and the other using the proposed GaN driver. Experimental results show that the GaN-based prototype achieves a power-added efficiency of 81.1%, which is 10.7% higher than the logic gate counterpart, and superior harmonic suppression.