Power MOSFETs (Metal Oxide Semiconductor, Field Effect Transistors) differ from bipolar transistors in operating principles, specifications, and performance. In fact, the performance characteristics of MOSFETs are generally superior to those of bipolar transistors: significantly faster switching time, simpler drive circuitry, the absence of or reduction of the second-breakdown failure mechanism, the ability to be paralleled, and stable gain and response time over a wide temperature range. This note provides a basic explanation of general MOSFET characteristics, and a more thorough discussion of structure, thermal characteristics, gate parameters, operating frequency, output characteristics, and drive requirements.