Power electronics are used to transform electrical energy from one voltage and/or frequency to another using a network of semiconductor switches and filter elements. Typical implementations include DC-DC converters in electric cars, DC-AC converters in solar photovoltaics, or AC-DC converters in desktop computers. Nonlinear transmission lines (NLTLs) that can compress a wide, low-voltage pulse into a sharp, high-voltage pulse may one day add another dimension to power electronics. The NLTL is of simple build, comprising varactors (nonlinear capacitors) and inductors in a ladder network and thus can possibly bring an advantage of compact implementation for select applications. To handle the high voltage on the line, wide bandgap (WBG) semiconductor pn junction diodes can be used as varactors. This chapter discusses the design and implementation of high-voltage NLTL prototypes utilizing WBG diodes.