Hello Friends
did you know how can I generate square signal with "arduino_uno_r3" and generate current (2 ampers) on the output without changing input voltage ...
we need just some ideas please 
thank you
( we have tried to put a voltage follower but the problem that we can only reach 60 mA with adding a charge on the output of this one ...)
So you need a square wave capable of.... sourcing 2A or sinking 2A, or both?
If you only need to source or sink , just use the signal to drive a logic level MOSFET (p-channel if switching high side, n-channel if switching high size). If you need high current for both sourcing and sinking, that's a little trickier...
Note that you will need an external power supply no matter what.