C1 is a bypass capacitor that helps prevent oscillation—yes, a circuit like this can oscillate—I connected a scope to it to prove to myself that it was stable. C2 filters out the AC wall wart ripple ...

2. TDA2003 Circuit. This 6V to 12V converter circuit is made with an IC from SGS with several additional components. The IC is a TDA2003 but it can be replaced with a TDA2002. The cost of building the ...

All flashlights I see these days have 3 to 24! white LED and only use 3x 1.5V (or even the rechargeable 1.2V) batteries, and the ones I checked didn’t seem to have a bucket converter circuit.