Millimeter-wave (mmWave) power amplifiers (PAs) are critical building blocks in next-generation radar, satellite, defense, and 6G communication systems, where output power, bandwidth, and efficiency must be achieved under stringent size, weight, and power (SWaP) constraints. Among the enabling technologies, Gallium Arsenide (GaAs) and Gallium Nitride (GaN) continue to dominate due to their complementary strengths in linearity, noise performance, and high-power density. This talk will focus on design considerations unique to mmWave GaAs and GaN PAs, with particular emphasis on stability and biasing challenges at frequencies above 20 GHz. Unlike lower microwave designs, mmWave PAs are highly susceptible to low-frequency oscillations, odd-mode instabilities, and bias-induced resonances. To mitigate these, stability networks—ranging from RC shunt loading and resistive feedback to series loading and quarter-wave stabilization—must be co-optimized with matching and biasing schemes. Special attention will be given to the integration of stability networks with bias networks, where parasitics from bias chokes, decoupling capacitors, and high-impedance bias lines can introduce additional poles/zeros in the response, affecting both gain flatness and unconditional stability. The presentation will review practical approaches to stabilizing mmWave PAs without compromising efficiency or bandwidth, including the use of lossy transmission lines, broadband bias tees, and RC filtering strategies tailored for GaAs vs. GaN processes. Case studies will illustrate how bias network design impacts stability margins and overall PA performance, and how distributed versus lumped stabilization choices evolve with frequency. The session will conclude with a discussion of packaging and integration considerations, where bondwire inductances, via transitions, and LTCC/SiP bias routing play a defining role in amplifier stability at mmWave frequencies. Speaker(s): Asmita Dani, Room: 4021, Bldg: Sobrato Campus for Discovery and Innovation, Santa Clara University, 500 El Camino Real, Santa Clara, California, United States, 95054, Virtual: https://events.vtools.ieee.org/m/505939