Source/load pull investigation of AlGaN/GaN power transistors with ultra-high efficiency

This paper presents the investigation of highly performing AlGaN/GaN HEMT power transistors through source-pull and load-pull analysis using an active harmonic load-pull system. The advantages of the GaN technology together with the right terminations lead to power transistiors with promising output power and efficiency. When setting properly the first three output terminations, a drain efficiency as high as 84,3 % has been achieved at 2 Ghz while delivering 4.3 W of output power for a 1.2 mm device gate width. However, it has been seen that the achievement and the set of the optimum output terminations do not lead to the best device perfomance. When presenting such three optimum output impedances together with the proper second harmonic source termination, it has been demonstrated, that higher drain efficiency up to 88 % can be obtained delivering output power as high as 4.4 W and a power gain of 14.9 dB. Indeed the GaN HEMT used in this work has reached record peak drain efficiency of 90 % delivering output power of 3.5 W.