Class-F dual-fed distributed amplifier
The conventional distributed amplifier offers broad bandwidth but has low efficiency since half of the FET output power is wasted in an idle termination, and only one of the FETs is fully utilised. Further, such amplifiers are normally operated in the class-A mode which has an inherently low efficiency. The single-ended dual-fed distributed amplifier (SE-DFDA)  allows all the FET output power to be utilised. The work of Moazzam and Aitchison  only considered single-FET SE-DFDAs. The SE-DFDA concept can be extended to N FETs, and if the FETs are spaced 180", all FETs have identical loadlines, which can be chosen optimally . The SE-DFDA therefore allows efficient power combining of FET output power without using bulky multi-way power combiners . In the previous work on the power SE-DFDA, class-A  and class-B  operation was demonstrated. A class-F amplifier  can offer both high output power and high efficiency (up to 100% for ideal transistors). To date, the developments reported in the literature pertaining to class-F amplifiers have essentially only considered single transistor amplifiers. In this Letter we propose a class-F single-ended dual-fed distributed amplifier (SE-DFDA) configuration that combines several FETs. This proposal therefore partners the SE-DFDA power combining approach with the high efficiency of class-F- operation.