Im not too bothered about efficiency. It will be run from a mains transformer but the 12V DC needs to be turned on/off using a transistor and the motor will be connected with 64 LEDs (on the DC side). I can use a more powerfull transistor than normal but i dont want it to be using too much current.

Ill have a look for op-amp sinewave circuits. Ive not done much with op-amps before so this is the perfect learning opportunity