The voltage regulator is a useful and most common IC building block next to the op amp. The monolithic form of a voltage regulator has replaced the discrete version because of their advantages. The monolithic voltage regulator is uniquely suited for local regulation. Hence IC voltage regulators are invariably used now a day in almost all voltage regulators.
The IC (integrated circuit) voltage regulator is an electronic integrated device which provides a constant voltage regardless of changes in the load circuits. The output voltage is regulated by the internal circuitry so that it is relatively independent of the current drawn by the load, the line or supply voltage and ambient temperature. An IC based voltage regulator can be classified in different ways. A common type of classification is three terminal voltage regulator and five or multi terminal voltage regulator. Another popular way of classifying IC voltage regulators is by identifying them as linear voltage regulator & switching voltage regulator.