INDEX

POSITIVE VOLTAGE REGULATORS
This include 78xx voltage regulators. The most commonly used ones are 7805 and 7812. 7805 gives fixed 5V DC voltage if input voltage is in (7.5V,20V). You may sometimes have questions like, what happens if input voltage is <7.5 V or some 3V, the answer is that regulation won't be proper. Suppose if input is 6V then output may be 5V or 4.8V, but there are some parameters for the voltage regulators like maximum output current capability, line regulation etc.. , that parameters won't be proper. When I applied 3.55V input, i got around 3.5V. Remember that electronics components should be used in the proper voltage and current ratings as specified in datasheet. You can work without following it, but you won't be able to get some parameters of the component.Get datasheet from google by searching '7805 datasheet' or from www.alldatasheet.com Next task is to identify the leads of the 7805. So first u have to keep the lead downward and the writing to your side,see the figure below. You can see the heat sink above the voltage regulator.(1-input,2-gnd,3-output)

This is the same way of lead identification for all 3 terminal IC's (for eg. Power transistor).

The above diagram show how to use 7805 voltage regulator. In this you can see that coupling capacitors are used for good regulation. But there is no need for it in normal case( I never used these capacitors). But if you are using 7805 in analog circuit you should use capacitor, otherwise the noise in the output voltage will be high. The mainly available 78xx IC's are 7805,7809,7812,7815,7824.