how to calculate or predict the Mismatch of current mirrors in practice design?
we know two formulas in mirrors:  delta(I)/I=delta(W/L)/(W/L)+2*delta(Vth)/(Vgs-Vth)
                                                  delta(Vth)=0.1*tox / [ (WL)^0.5]

I don't know the Mismatch of  delta(W/L)/(W/L)  in practice MOS transistor, I didn't find the answer in kit's  design rule.
What are the rules of thumb on this  term?

As a roughly predict, I calculate the Mismatch like this:
                                                 delta(I)/I=2*delta(Vth)/(Vgs-Vth)
                                                 delta(Vth)=0.1*tox / [ (WL)^0.5]  
                                                 tox=0.35um/50=70A     ( for 0.35um  technology   )
                                                 Vgs-Vth=Vdsat=200mv
  So i get the following roughly formula to predict the Mistach:
                                                 delta(I)/I=14mV/{[ (WL)^0.5]*Vdsat}
                                                              =14mV/{[ (WL)^0.5]*200mV}

Did my couclusion correct or reasonable?
Are there any rules  of thumb about the Mismatch of current mirrors?
Thanks for help.  

Hi

I derive the formula " delta(Vth)=0.1*tox/[ (wl)^0.5 ] mV " from  "Design of analog cmos IC" by razavi,2001.  In chapter 13,  page 465,  equation 13.62.  
 
It seems that razavi also referenced the paper you adivsed.

Thanks.