An emitter follower to isolate MCU from load?
You do it as simple as this:






simulate this circuit &ndash; Schematic created using CircuitLab

The 1kΩ resistor at the base of the transistor feeds about 2mA@3.3V into the small signal NPN transistor, that's enough to saturate it for a collector current of up to 100mA. If you need more than that, consider a darlington NPN instead. VLED may be up to 50V or so, whatever your small signal NPN offers.