Diff pair-common centroid

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SP24

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I am trying to match the diff pair using common centroid.
Please go through the attached layout.

1.give suggestions to,improve this layout.
2.correct this layout If my approach is wrong with respect to matching or routing parasitics

Regards
SP24
 

Hello,

You can share the sources of the Transistor A & B, this way you will reduce area, minimize the no.of drain regions and also parasitics attached to them. With your current design you are introducing coupling cap between the metals by maintaining the source and drains far apart and also the diffusion cut can be avoided, which in turn can avoid cap's.

You can avoid 4 drain nets and can just have 2 drain nets by adding the 2 drain nets like the gate nets in between the 4 block segments. By this placement you will avoid metal cap coupling and also area & parasitics.

Hope this may serve some of your purpose.

Paramjyothi
 

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    SP24

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Hi Paramjyothi

Thanks for the valuable suggestion.I am working on 65nm tech.
I have placed the trans in such a way that they are arranged in a source/drain source/drain pattern so that the direction of current flow will be uniform.

It will be of great help if you could tell me which is dominant?
current direction or the routing induced parasitics since i may be in wrong assumption about the matching constraints.
 

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