The Designer's Guide Community Forum

The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl
Simulators >> Circuit Simulators >> Monte Carlo: Mismatch and area
https://designers-guide.org/forum/YaBB.pl?num=1233089626

Message started by idesign on Jan 27^th, 2009, 12:53pm

Title: Monte Carlo: Mismatch and area
Post by idesign on Jan 27^th, 2009, 12:53pm

in Monte Carlo analysis, the variation between two devices on the same die due to random mismatch is inversely proportional to the square root of the device area: sigma ~ 1/sqrt(Area).
If the transistor is made of multifingers, should I consider the total area or one finger area? An answer and a reference will be much appreciated.
Thanks

Title: Re: Monte Carlo: Mismatch and area
Post by Tlaloc on Jan 27^th, 2009, 6:46pm

It is due to the total area including all fingers and multiples. This is due to averaging effects since with larger areas, you are more likely to get areas of the device that are shifted in opposite directions that then tend to cancel.

Title: Re: Monte Carlo: Mismatch and area
Post by wave on Jan 28^th, 2009, 2:33am

Agreed - consider total area.
Layout stripes so you don't introduce something systematic, which is not modeled. (That's another can of worms - Ref: Bob Pease)

M. Pelgrom, JSSC, wrote the classic matching paper with the eqn you cite.