The single-ended primary-inductor converter (SEPIC) is capable of operating from an input voltage that is greater or less than the regulated output voltage. Aside from being able to function as both a buck and boost converter, the SEPIC also has minimal active components, a simple controller, and clamped switching waveforms that provide lownoise operation. The SEPIC is often identified by its use of two magnetic windings. This paper looks at each approach and discusses the impact each has on a practical SEPIC design.