Cadence differential pair layout

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bestvlsi

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Hi all ,

I ve to do layout for a differential pair with 2 fingers each.

Now i read that for differential pair we should go for common centroid which means if the transistors are named A and B. Then

AB
BA

is the desired layout.

But i also read on the forums in some other posts that if the the number of fingers is small then to reduce routing complexity ... we can simply go for interdigitization ..

My question is in my case since the number of fingers is low ... can I go for only interdigitization?

Regards.
 

My question is in my case since the number of fingers is low ... can I go for only interdigitization?
Click to expand...

Ofcourse you can.You can try those patterns : ABBA (or this as a column,i mean ABBA vertically) or do both interdigitization and common centroid :
AB
BA
 
Last edited:
Thanks a lot jimiti13
 

For Diff Pairs we prefer cross coupled matching.
AB
BA
 

Funda behind doing matching is to compensate the effects due to process variations..
If number of fingers are less then we can say almost all devices sit in same place on the wafer..
If the devices are large then best thing is to increase the number of fingers and do common centroid matching..
 

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