GaN HEMT Darlington Power Amplifier with Independent Biasing for High-Efficiency Low-Distortion Wide-Dynamic-Range Adjustment

Wide-dynamic-range operation for high-efficiency and low-distortion characteristics has been realized with a novel independently biased GaN HEMT Darlington power amplifier. The nonlinearity of each GaN HEMT has been successfully cancelled to reduce third-order inter-modulation distortion (IMD3) for the wide dynamic range by means of independently adjusting each gate bias voltage. Without affecting the IMD3, power-added efficiency (PAE) can be optimized with independent drain voltage supplies. Thus, high-efficiency and low-distortion characteristics can be simultaneously realized with the proposed Darlington power amplifier. The fabricated GaN HEMT Darlington power amplifier exhibited a PAE of 36% and an IMD3 of -35 dBc with an output power of 30 dBm at 1.45 GHz. A high quality of 64-QAM constellations has been retained for an output power range from 20 to 32 dBm.