Every system needs power supplies and one or more low-voltage rails, of course, but deciding on the appropriate distribution topology and combination of DC/DC regulators and modules to supply the power can be confusing and often frustrating. This Fundamentals course looks at the critical issues, tradeoffs, and choices among LDOs, discrete regulators, and complete modulators in terms of performance, size, efficiency and other factors. It also looks at available tools which can help the designer assess the choices and options in making both the overall topology and component-selection decisions.