eldo_user

Monte Carlo Analysis
Tolerance Setting Using DEV, DEVX or LOT
.MODEL N NMOS VTO=0.6 TOX=1.5e-7
.MCMOD N VTO DEV=0.1
DEV Variation
DEV variation specified with .MODEL statements (or .MCMOD) can refer to dimensions of the
current object directly, without any need to encapsulate models into subcircuits. The syntax for
accessing an instance parameter is for example:
E(*,)
The * character is used here to refer to the current instance.
Example
.MODEL M nmos VTH=1 DEV={sqrt(E(*,l)*(E(*,W))*1.0e-5}
M1 p1 p2 p3 p4 m w=10u l = 3u
The two lines above are equivalent to the five below:
.SUBCKT foo d g s b param: w=1u l=1u
.model m nmos VTH=1 DEV={sqrt(l*w)*1.0e-5}
M1 d g s b m w=w l=l
.ENDS
X1 p1 p2 p3 p4 foo w=10u l=3u
A full example to illustrate this:
* test DEVX
M1 D1 G1 0 B mos1 w=w l=l as=0 ad=0 ps=0 pd=0 m=1
M2 D2 G2 0 B mos1 w=w l=l as=0 ad=0 ps=0 pd=0 m=1
.MODEL mos1 nmos
+ level=53 version=3.24
+ u0=300 tox=5n
+ vth0=1 DEV={sqrt(E(*,l)*(E(*,w)))*1.0e-05}
.param l=5e-6 w=10e-6
.op
.MC 10
.option display_carlo EXTMKSA
Tolerance Setting Using DEV, DEVX or LOT
The size of the tolerance appears in a .MODEL command after the parameter keyword and
value. The tolerance may be specified either as a percentage or an absolute quantity. To denote
a percentage, the % sign must be used. Parametric expressions are allowed when specifying
DEV or LOT.
The DEV tolerance parameter causes devices which use the same .MODEL statement to vary
independently of each other, as illustrated in the following example:
c1 4 0 cmod 10p
c2 6 8 cmod 10p
.model cmod cap dev=10%
Eldo® User's Manual, 15.3 447