The LM317 is a three-terminal tunable positive voltage regulator integrated circuit from National Semiconductor. The output voltage range of the LM317 is 1.2V to 37V and the load current is up to 1.5A. It is very simple to use, only two external resistors to set the output voltage. In addition, its linear adjustment rate and load adjustment rate are better than standard fixed regulators. The LM317 has a built-in overload protection circuit.