Other micro-controller uses 5v as standard input voltage, many latest device modules, popular sensors, GPS, RF modules, Flash Memories, SPI storage, Display, use 3 to 3.3v most of this devices requires logic level conversion to protect them from high voltage
Wiring MOSFET to Arduino and Driving Bigger Loads
Each one of Arduino Pins can be used to power devices that use up to 20 mA, this is a very small amount of current to drive, just enough to run an LED. If you try working to drive something