This application note focuses on the fundamentals of inductor-based switchmode power converters. This is a grassroots approach to understanding switchmode power converters. Specifically, the basic buck circuit topology and its associated waveforms will be examined both empirically and mathematically. All known switchmode power converters can be derived from combinations of the basic buck and/or boost converters along with some form of transformation function. Roughly 85% of today’ switchmode power converters are derived from the buck topology. Understanding its operation is essential to switchmode power converter design.