Methods for constant current (no PWM) in driver design (not existing drivers)

Not having much clue about electronics, I had a look into the intl-outdoor colour MC-E driver, which seem to work with transistors, perhaps that is a way to go?? I stopped going any further with it (want to find out the maximum current that can be achieved with these transistors before they really blow), but I am still planning to go on with it some day..