A 6–18 GHz GaN pHEMT power amplifier using non-foster matching

Non-Foster matching is applied to design a multi-octave broadband GaN power amplifier (PA) in this work. The bandwidth limitation from high-Q interstage matching is mitigated through the use of negative capacitor, which is realized with a negative impedance converter (NIC). Detailed analysis is presented to understand the frequency and power limits of NIC circuits for PA application. A 6-18 GHz power amplifier fabricated with 0.25-μm GaN pHEMT process shows the output power reaching 35.7-37.5 dBm with 13-21% PAE. The NIC boosts the efficiencies and power below 11 GHz to achieve broadband performance without the use of any lossy matching circuits or negative feedback. To our knowledge, this is the first demonstration of NIC-based broadband amplifiers with Watt-level output power.