The efficiency of a synchronous step-down power converter with integrated or external MOSFETs can be optimized when the designer understands the parameters that affect efficiency and the specifications to look for in data sheets. In the absence of an ideal power converter, the designer has to make trade-offs and optimize the parameters that affect power-supply efficiency. A wide portfolio of discrete MOSFETs is available from Texas Instruments, including power blocks (dual-MOSFETs in one package) and power stages (gate driver and dual-MOSFETs in one package). This paper revisits some of the basic principles of power supplies and then addresses how MOSFETs—the power stage of any switching-voltage regulator—affect efficiency.