This course can also be taken for academic credit as ECEA 5721, part of CU Boulder’s Master of Science in Electrical Engineering. This course is primarily aimed at first year graduate students interested in engineering or science, along with professionals with an interest in power electronics and semiconductor devices . It is the first course in the "Semiconductor Power Device" specialization that focusses on diodes, MOSFETs, IGBT but also covers legacy devices (BJTs, Thyristors and TRIACS) as well as state-of-the-art devices such as silicon carbide (SiC) Schottky diodes and MOSFETs as well as Gallium Nitride (GaN) HEMTs. The specialization provides an overview of devices, the physics background needed to understand the device operation, the construction of a device circuit model from a physical device model and a description of the device fabrication technology including packaging. This first course provides an introduction to semiconductor power switches, including a classification based on power switch properties, a description of key power switches, an overview of device data sheets, and the identification of on-state and power losses of diodes and MOSFET individually and in a power convertor circuit. It provides the link between power converter applications and individual devices, through analysis and simulation and prepares learners for the in-depth device analysis of the other courses in the specialization.