A voltage regulator is a circuit that supplies a constant voltage regardless of changes in load currents. Although voltage regulators can be designed using op-amps, it is quicker and easier to use IC voltage regulators. Furthermore, IC voltage regulators are versatile and relatively inexpensive and are available with features such as a programmable output, current/voltage boosting, internal short-circuit current limiting, thermal shutdown, and floating operation for high-voltage applications. IC voltage regulators are of the following types:
Except for the switching regulators, all other types are of regulators are called linear regulators. The impedance of linear regulator's active element may be continuously varied to supply a desired current to the load. On the other end, in the switching regulator a switch is turned on or off at a rate such that the regulator delivers the desired average current in periodic pulses to the load. Because the switching element dissipates negligible power in either the on or off state, the switching regulator is more efficient than the linear regulator. Nevertheless, in switching regulators the power dissipation is substantial during the switching intervals (on to off or off to on). In addition, most loads cannot accept the average current in periodic pulses. Therefore, most practical regulators are of linear type.
Voltage regulators are commonly used for on-card regulation and laboratory-type power supplies. Voltage regulators, especially the switching type, are used as control circuits in pulse width modulation (PWD), push-pull bridges, and series type switch mode supplies. Almost all power supplies use some type of voltage regulator IC because voltage regulators are simple to use, reliable, low in cost, and, above all, available in a variety of voltage and current ratings.
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