Design of GaN‐based X‐band LNAs to achieve sub‐1.2 dB noise figure

GaAs and SiGe technologies take an edge over GaN‐based devices in terms of better noise figure (NF). In this article, we present HEMT topologies and design techniques to achieve a sub‐1.2 dB NF for a GaN‐based X‐band low‐noise amplifier (LNA). This NF is comparable with state‐of‐the‐art reported works in competitive GaAs and SiGe technologies. Moreover, this is the best reported NF in X‐band using GaN technology to date. Two LNAs are fabricated using in‐house 0.15 μm AlGaN/GaN on the SiC HEMT process. LNA‐1 has inductive source degenerated (ISD) HEMTs at both stages, while LNA‐2 has ISD HEMT at the first and common source at the second stage. The significance of ISD HEMT, for the first or subsequent stages in a multi‐stage design, towards NF improvement is addressed. The criticality of stability networks towards NF contribution and its design is discussed in detail. Furthermore, even‐mode stability of each HEMT after complete LNA design is assured using the S‐probe method in Pathwave Advanced Design Systems.