pull down resistor design

[surreyian]

Hello,

Im trying to figure out how to design my pull down resistor using NMOS transistor.
Pull down current is 5uA(max) with at 3V. How should I size the transistor, in order to get 5uA. currently using 2 cascoded NMOS with L(at max) and W (at min).
Please advice on design.

 

[alenhan]

use long cannel device

 

[dwilliam]

You can use a simple NMOS current sink.