I did this a few years ago and blogged it in my watsonseblog, now gone for more than a year. I guess it’s about time I did it again. The circuit is the two transistor circuit with a 2SD639 high current transistor for the output – it’s the same circuit I used in the flashlight in this blog. It can push a lot of current through the two LEDs connected in series.
I don’t remember where I got the schematic, but it is not the typical two transistor circuit. It does not use a coupling capacitor between the output and input. The resistance values are unusual, too. But it works.
