Ok, this may sound like a stupid question, but I need a little help. I'm building a circuit board that uses components for 12v and 5v. The main power is a 12v 8a source so I need to add a step down to my circuit for the 5v devices.
I've seen two diagrams: http://www.eleccircuit.com/wp-content/uploads/2009/09/12v-to-5v-3a-dc-converter-step-down-regulator.jpg http://www.eleccircuit.com/wp-content/uploads/2009/09/dc-power-supply-5v-and-12v-using-2n3055-lm309.jpg
Both look legit except the first that says it take 12v 3a and not 8a. I don't know if it will still work. Next is I'm not sure where to find/buy the transistors. Every time I do a google search, I end up with mixed results. Is it just a matter of getting a hold of NPN transistors or is there another aspect I need to look at. I'm about to make a purchase from sparkfun, so preferably I'd like to be able to order all my parts from there.