programmable current source

[arup172]

i have made a programmable current source which can source current from 10uA to 2A.i have used a DAC to drive an op amp and mosfet configuration.the problem is that the current needs to be sourced into a node whose voltage can swing from 0 to 5V and for such a large range the mosfet doesnt work in saturation and the current varies with the node voltage.
Can anyone please suggest a solution?

 

[mengcy]

You'd better present your schematic here.

 

[BABESH]

current source 2a

10u to 2A is very wide range can you post schematic... i will try to figureout if possible..

--babesh