Hi Jacopo

finding an example was harder than I thought.

"make your own opto transistor"

http://www.instructables.com/id/Laser-powered-burglar-alarm/step9/Make-the-=
photo-transistor/

AC126 is an old germanium transistor. The TO-18 can does
not contain anything but the die (ie no paste), which you can
cover with epoxy or lacquer

http://en.wikipedia.org/wiki/Phototransistor#Other_modes_of_operation

The ones that I used to modify were the silicon BC107, BC108
and BC109, which were around before the BC547, 548 and 549
TO-92 plastic versions, and very much cheaper than the TO-18
opto transistor I'm sure has pretty much the same die.

My main use was for guitar effects pedals, using a small 6V torch
bulb as the light source. Couldn't tell the difference between a home-
made opto transistor and the expensive specified one

Joe=20

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