Editing Linear regulator (section)

==Using a linear regulator==
Linear regulators can be constructed using discrete components but are usually encountered in [[integrated circuit]] forms. The most common linear regulators are three-terminal [[integrated circuit]]s in the [[TO-220]] package.

Common voltage regulators are the LM[[78xx]]-series (for positive voltages) and LM79xx-series (for negative voltages).  Robust automotive voltage regulators, such as LM2940 / MIC2940A / AZ2940, can handle reverse battery connections and brief +50/-50V transients too.  Some [[Low-dropout regulator]] (LDO) alternatives, such as MCP1700 / MCP1711 / TPS7A05 / XC6206, have a very low quiescent current of less than 5 μA (approximately 1,000 times less than the LM78xx series) making them better suited for battery-powered devices.

Common fixed voltages are 1.8 V, 2.5 V, 3.3 V (for low-voltage [[CMOS logic]] circuits), 5 V (for [[transistor-transistor logic]] circuits) and 12 V (for communications circuits and peripheral devices such as [[disk drive]]s). 

In fixed voltage regulators the reference pin is tied to [[ground (electricity)|ground]], whereas in variable regulators the reference pin is connected to the centre point of a fixed or variable voltage divider fed by the regulator's output. A variable voltage divider such as a [[potentiometer]] allows the user to adjust the regulated voltage.