So I have been diligently working toward coming up with this circuit on my own for a week, once I did, I discover it diagrammed out online... figures. Goes to show once you know enough to ask for what you want, you can usually make it yourself. Which brings me to my current question. I need a circuit like this with four channels minimum, which I could easily make using my four tip121's, but then I would have four big floppy transistors swinging in the breeze. What I really want is something smaller to do the same thing several times, like a uln2003a. The trouble is, the pins you can access on the uln2003a are the base and emitter, which won't invert the logic. I need something that gives you access to the base and collector and simply gangs the emitters to one pin, so I can make several of these circuits using just one chip. Ideas?