This is actually for disco lights. Im making some that use some full color LEDs. I checked the datasheet of the LEDs and it appears the Red, Green and Blue use 30mA, 25mA and 30mA respectively. The datasheet for my PIC says each IO pin can only take 25mA. I will be using 17 of these LEDs on each light and they have to be wired in parallel so thats way too much current for the PIC to handle. I decided to add some transistors in and they seem to work although im using NPNs at the moment when i should be using PNPs. About 2.5V seems to get the LEDs to the correct brightness without overheating but to reduce the overall current needed im flashing them very fast between Red, Green and 2 Blues so each color is on for 1/4 of the time. Someone on here told me that means i can use 4 times the voltage because it averages out to what it was origionally. I tried that and it seems to work fine.

I would like to use transistors rather than a chip because the PCB is going to be extremely small and transistors can be dotted about where they are needed (2 on each side). I definately have room for 4 transistors but i cant make the PCB any bigger. To make things even more interesting its a round PCB!

Im pretty sure i would want a darlington pair type of transistor. Thats what im using at the moment for other projects and they do the job pretty well. There are 2 problems with them though. The first is that they are NPN and the second is that Rapid have suddenly stopped selling them. I would like to use NPN transistors but the LEDs i have are common cathode