I've made a simple circuit to step down voltage from 12V+ to around 5V, and while it works, it is noisy and it requires much capacitance. I would prefer to make it using transistors instead of relays. I would like to replicate whenever I want, with salvaged pieces, so I want to avoid voltage regulators ic's.
Circuit running:
http://postimg.org/image/m97k4ugg7/
I've tried to do it myself but I failed with transistors (mosfets). I think it requires to have a part that would act like a current sensor but I don't have the knowledge to make it.
simulate this circuit – Schematic created using CircuitLab
Best Answer
Try this:
simulate this circuit – Schematic created using CircuitLab
It's a simple voltage-follower circuit. The base of Q1 is held at 5.6V by D1, and the emitter is about 0.65V lower, or very close to 5.0V.
It'll deliver almost 2A at 5V, assuming you put a heatsink on Q1 that can handle the 15W of heat produced.