is this the same scheme right? Because i get confused with more resistors... i found an opamp rail to rail "1,8 to 6 volt range" NJM2732D. is it better?
There is also an opamp NJU70 series. For exemple the NJU7095D wich can work from 1 volt to 5,5 volt. but it's not rail to rail. Does it matter?
It's a similar concept, but missing the parts to set the current (via the control voltage).
The opamp must be a type that can provide enough output current to drive the transistor. The one I picked has an output current of up to 80 mA which is quite rare.
The opamps you mention have much lower output current ratings & could not directly drive a power transistor, sorry..