A differential analysis of electrical attributes, including the temperature profile and trapping phenomena is introduced using a device analytical spatial electrical model. The resultant current difference caused by the applied voltage variation is divided into isothermal and thermal sections, corresponding to the instantaneous time- or temperature-dependent change. The average temperature relevance is explained in the theoretical section with respect to the thermal profile and major parameters of the device at the operating point. An ambient temperature variation method has been used to determine device average temperature under quasi-static state and pulse operation, was compared with respect to the threshold voltage shift of a high-electron-mobility transistor (HEMT). The experimental sections presents theoretical subtractions of average channel temperature determination including trapping phenomena adapted for the AlGaN/GaN HEMT. The theoretical results found using the analytical model, allow for the consolidation of specific methodologies for further research to determine the device temperature based on spatially distributed and averaged parameters.