Comparison of a single and a dual-gate GaN switching-amplifier for future communication systems

A high efficiency switch-mode amplifier with a dual-gate configuration in the output stage is designed in a 250 nm GaN HEMT technology. Measurements are performed up to 8 Gbps using periodic square wave signals and bandpass delta sigma (BPDS) signals. The results are compared to a single-gate amplifier which uses the same driver stage and gate width. The dual-gate amplifier achieves a higher output power and shows a better RF-performance at bit rates above 2 Gbps. A broadband output power of 14 W and a PAE of 77.5 % at 0.9 Gbps are demonstrated. Furthermore, a 5.2 Gbps BPDS signal with an eye amplitude of about 50 V is measured. It is the first time that such high amplitudes are achieved in combination with bit rates above 5 Gbps. The presented measurement results demonstrate the importance of GaN devices for future switch-mode amplifiers.