help needed with parametric analysis in spice

[abhii]

i need to do a parametric analysis in spice to show the different drain current curves with varying channel length of NMOS. But i am getting an error can anyone plz help me out

vds 1 0 5v
vgs 2 0
m1 1 2 0 0 n1
.param l_val = .1u
.model n1 nmos level = 2 tox = 50n nsub = 1e16 l = l_val w = 10u
---------------------------------------------------$
ERROR -- 'l_val' is not a model parameter name
.dc vgs 0 5 1 sweep l_val .1u 10u .5u
--------------$
ERROR -- Must be 'I' or 'V'
.probe
.op
.end

 

[LvW]

I suppose, you forgot to define l_val as a "global parameter" which is to be varied.

 

[abhii]

well how do i do that?and besides doesn't the statement .param l_val specify that l_val is a global which will be varied?

 

[LvW]

Which SPICE simulation package are you using?
For example, in PSpice you have to declare one part as a global parameter and - more than that - specify any value for it (nominal).

 

[abhii]

I am using PSpice student version

 

[LvW]

Hu abhii,

I am not sure, but perhaps you can vary one parameter within a model statement only via a tolerance specification (as, for example, for a Monte carlo simulation).

 

[keith1200rs]

The problem is not to do with global.

I am not sure of the Pspice syntax but I would think the problem is more likely to be to do with the syntax of l=l_val - some simulators want either single quotes, curly brackets or square brackets around the variable so l='l_val' for example.

Keith