Hello. Is there any way to know Avt(threshold voltage mismatch parmeter) and Abeta in Gf180mcuD nmos3.3V device?

$PDK_ROOT/gf180mcuD/libs.tech/ngspice/sm141064.ngspice

line 47015 is the

nfet_03v3

model:

.subckt nfet_03v3 d g s b w=1e-5 l=2.8e-7
+ as=0 ad=0 ps=0 pd=0 nrd=0 nrs=0 par=1 dtemp=0
+ sa=0 sb=0 nf=1 sd=0 m=1

.param
+ par_vth=0.007148
+ par_k=0.007008
+ par_l=1.5e-7
+ par_w=-1e-7
+ par_leff='l-par_l'
+ par_weff='par*(w-par_w)'
+ p_sqrtarea='sqrt((par_leff)*(par_weff))'

.param
+ var_k='0.7071*par_k* 1e-06 / p_sqrtarea'
+ mis_k=agauss(0,var_k,1)

.param
+ var_vth='0.7071*par_vth* 1e-06 / p_sqrtarea'
+ mis_vth=agauss(0,var_vth,1)

m0 d g s b nfet_03v3 w=w l=l as=as ad=ad ps=ps pd=pd nrd=nrd nrs=nrs
+delvto='mis_vth*sw_stat_mismatch'  sa=sa sb=sb nf=nf sd=sd m=m
.ends nfet_03v3

The Vth mismatch is parameter

delvto

and is based on the values

mis_vth

,

var_vth

, and

par_vth

.

@Tim Edwards there is a bug in the model that gives wrong mismatch results when the multiplier is used. Please check this article for a detailed explanation: https://www.linkedin.com/pulse/why-using-device-multiplier-can-make-your-monte-carlo-hesham-omran/

@Hesham Omran: Thank you for pointing that out. Most foundry PDKs (like sky130, for example) define a parameter like

mult

which is set to the same value as

m

; the difference is that

mult

can be used inside expressions but

m

cannot. I agree that the model should define

mult

and define area as

mult*par_leff*par_weff

. Otherwise, multiplicity is not factored into the area for mismatch analysis.

@Tim Edwards @Hesham Omran Thanks, all of you :)