First invented by Nikola Tesla in 1891, the Tesla coil supplied high voltage at low current, demonstrating spectacular arcing discharge many feet long. However, the coil has been used more for demonstration and entertainment, and less for teaching and research, mainly because of its inherent dangers. The dangers have been largely removed with today’s diodes and transistors, allowing improved safety, as demonstrated by the authors in 2022. The improved miniature Tesla coils built by the authors over 2021–23 better lit a nearby fluorescent lamp, made a common filament bulb act like a plasma ball, and produced an imperceptible continuous discharge on the finger. The constructed miniature Tesla coil better demonstrated (over past models) boosting of voltage and other electrical principles. Improving performance by changing parameters such as capacitors and spark gap have been discussed. A comparison has been made for the three successively improved Tesla coils built by the authors.