This thesis presents the design and characterization of a modular power stage using Gallium Nitride (GaN) transistors for automotive three-phase inverter applications. The project was carried out as an internship at Ideas & Motion, in collaboration with the Politecnico di Torino, with the aim of creating an efficient, compact and reliable inverter system suitable for high-power demands in electric vehicles. GaN technology was selected due to its high voltage capability, fast switching speed and superior efficiency compared to traditional silicon-based systems, making it ideal for the rigorous requirements of automotive power electronics. The work begins by examining the technological and environmental motivations driving the electrification of transportation, as well as the fundamental principles of power conversion and the advantages of wide-bandgap devices.