Overview

Linear power supplies are the simplest of the DC/DC converters, but don't be fooled by the apparent simplicity of them. There are several factors in every application of linear supplies that are important for their reliable operation. These are thermal design, output regulation, stability considerations and its transient response, any of which could cause the system to behave badly.

Linear regulators are used much more often than switching regulators. One finds them distributed throughout products as POL (point of load) supplies, where local circuit regulation is needed, voltage bus quieting for noise sensitive circuits, and inexpensive voltage bus generation.

If you have done a design completely using linear regulators, you may technically call yourself a "power supply designer," but you will not fully appreciate the complexities of the field until you have experienced a switching power supply design. You have only reached the "tenderfoot" level of experience.

I've attempted to cover the material in a succinct and intuitive manner showing how flexible the humble linear regulator can be. The design examples can be scaled and adapted to many other applications. Related topics such as thermal design can be found in chapter 12.

Marty Brown

The linear regulator is the original form of the regulating power supply. It relies upon the variable conductivity of an active electronic device to drop voltage from an input voltage to a regulated output voltage. In accomplishing this, the linear regulator wastes a lot of power in the form of heat, and therefore...