A Dual-Mode Bias Circuit Enabled GaN Doherty Amplifier Operating in 0.85–2.05GHz and 2.4–4.2GHz

We report an ultra-wideband and high efficiency sub-6GHz power amplifier, which is based on multi-band Doherty load modulation. Key novelty is that a dual-mode bias circuit which operate as frequency-dependent compensating circuit at a half of center frequency 0.5f₀ mode, and DC-block and RF-choke at a center frequency f₀ mode. The amplifier using 0.15-µm GaN HEMT FETs achieved drain efficiency of 41.4–58.2% over 0.85–2.05GHz with 0.5f₀ mode, and 43.5–62.1% over 2.4–4.2GHz with f₀ mode at 6dB power back-off. This, to the best of authors’ knowledge, is the widest coverage of frequency reported so far for a multi-band Doherty amplifier at these carrier frequency range. It is a very promising PA technology for sub-6GHz base station, enabling reduction of the total cost of ownership (TCO) for operators.