??? What are you trying to do drop voltage for a LED or for something else. You need to know a few things like what is your sorce voltage, AKA say your source is +5 Volts, Then you need to know the Foward Voltage, AKA the opperating voltage of what ever it is your trying to power. Then you need to know what type of current your item needs aka 25 mili amps.
Provide me some more information I'll see if I can help you. If its something your working on and you don't want anyone else to know then PM me.