Step 1: A little insight....
The Darlington transistor, or more commonly, the Darlington pair, consists of two separate bipolar transistors sharing a common collector, and when combined, offer an exponentially higher gain than both transistors separate.
The idea was created by engineer Sidney Darlington of Bell Labs in 1953. He also patented the idea of having 2 or 3 transistors on a single chip,sharing a collector pin.
In a way, the pair could be seen as operating in 2 ways. The 1st, and most commonly accepted, is where both transistors act like amplifiers, the 2nd stage further strengthening the output of the 1st stage. I have a slightly different view of it, where the 1st stage acts as an amplifier, beefing up the input, so that it saturates the base of the 2nd stage, turning it on, like a switch.
With all that being said.... LETS BUILD SOMETHING!!!!!!!!!