Significance

• Voltage regulators compare a power supply's output with a fixed voltage. They are able to automatically adjust the output to a desired level called a reference voltage. Power supplies that use them are called regulated, and ones that don't are called unregulated.
  
  

Features

• IC voltage regulators are made using semiconductors. They are small and lightweight. They have three leads, and a metal tab to dissipate heat. They usually require resistors, capacitors and an external heat sink.
  
  

Fixed vs. Adjustable

• IC voltage regulators are fixed or adjustable. Fixed regulators yield a constant positive or negative reference voltage. Adjustable regulators can vary in reference voltage.
  
  

Fixed IC Regulators

• Popular fixed positive IC regulators are the LM78xx series. Negative IC regulators are the LM79xx series. The letters "xx" represent the output voltage, and so 7806 means a positive 6-volt reference voltage, for example.
  
  

Adjustable IC Regulators

• A common adjustable IC is the LM317. Its output regulated voltage can be up to 37 volts. The LM337T outputs regulated negative voltages from --1.2 to --37 volts.
  
  

Uses

• IC voltage regulators are used in power supplies and surge protectors. They are found in devices such as car alternators, and laptop and cell phone adapters.