1-8 GHz high efficiency single-stage travelling wave power amplifier

This paper describes a Class-A/AB wideband power amplifier that comprises of a single-stage transistor travelling wave structure in which capacitive coupling and frequency dependent lossy artificial-line are employed at the input of the active device. The proposed technique significantly enhances the amplifier's gain-bandwidth product, input match and gain flatness performance. To ensure the amplifier delivers a predefined power to the load over its entire operating band 2-to-8 GHz a broadband load-pull technique was applied at the output of the amplifier. To avoid reduction in the amplifier's bandwidth resulting from parasitic capacitive effects associated with the off-chip choke inductor a wideband RF choke was designed. The 1.31 x 2.93 mm(2) power amplifier was fabricated using 0.25 mu m GaAs pHEMT MMIC process. The measurement results show that the proposed amplifier delivers an average P (sat) of 29.5 dBm and P (out,1 dB) of 26 dBm, and the corresponding PAE levels are 55 and 35 % for the P (sat) and P (out,1 dB), respectively.