power transistor apps

An "electronic" ballast can replace the simple inductive ballast in most, if not all, gas discharge type lamps. These electronic ballasts need to be carefully designed to work properly and efficiently. They need to be a bit more complex than a simple transistor CCS.

http://en.wikipedia.org/wiki/Sodium-vapor_lamp#Theory_of_operation

http://en.wikipedia.org/wiki/Electrical_ballast