Making a Darlington transistor (eg: TIP120) with D882 to drive 12V LEDs with 3.3V or 5V input RPi
If you just need a surface mount version of a tip120, the MJD122 would work, but I would recommend the fallowing to protect your GPIO from the 12V, which is 3.3V i/o on a raspberry pi.



simulate this circuit &ndash; Schematic created using CircuitLab
But either way, the efficiency of using a transistor with this micro controller board is not going to be that good to begin with. Now, if we use an enhancement mode MOSFET instead of a darlington, then the low voltage cmos from the raspberry pi (2.5V logic hi) would drive the circuit efficiently, and more like a switch. So I would recommend for raspberry pi, this kind of driver circuit:



simulate this circuit