Idrive spread measurement

[airace]

Hi,
I am trying to measure Idrive process spread for PMOS/NMOS (TSMC 0.18um). The test setup i have used is below :-

The NMOS size i used is actually 50/0.18..and simulation is with specter with conditions being Vgs =1.8 and Idrive to be measured at Vds = 1.8 v

Problem : Id is reaching Imax/Imelt of source - bulk region before Vds = 1.8v and specter linearizes the result in this region and results are wrong.
If I put in a current limiting resistor, it will vary the DC bias point of X'tor..
can someone suggest any alternative setup/workaround.. :roll:

Any help will be appreciated.
Thanks!

Regards,
@ir@ce

 

[airace]

..also forgot to mention that, I am measuring cirrent thro' dummy voltage source...to find Idrive.

Regards,
@ir@ce

 

[Colbhaidh]

Looks like you havce set W to zero on the schematic ?

 

[airace]

....No!..Have set it to 50u...this was a sample schamtic i made for the post