As the name suggets it regulates voltage tat is it can provide either constant voltage r variable voltage(DC only)
Fixed Voltage regulators (78xx,79xx) [7805 being the most popularly used ]
Variable Voltage regulator (LM 317)
Fixed 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).If the voltage is below 7.5 V u mite get the output voltage as 4.6-4.8 V.
This is how 7805 luks like:
IN is the 1st pin where u give the + of power supply OUT is where u get 5 V o/p + and COM is where u give the negative terminal of the power supply , n take it again as the - ve of 5 v o/p.
CHECK BELOW FOR THE CKT DIAGRAM
Its not really not necessary to use those capacitors , I never used them .
It will be the same for - ve voltage regulators , I will talk abt variable voltage regulators in my next post