For the work experiences general that want power supply LAB. I thinks L200 DC Variable power Circuit. May like you , because of give Volt range about 3V-15V and Current 2A normal. When , you see the circuit. May search eyes and the integrated circuit that use be number L200 although old already. But still be usable well the interesting. This important circuit that should use Transformer that be appropriate be 12V sizes and should use 2A more than because get current that straight follow want certainly give testimony grandmother horn forget to stick let off the heat gives with, IC L200 with appropriately. The detail is other see in the circuit and from original website http://www.mitedu.freeserve.co.uk/Circuits/Power/l200var.html