Adding Dummies for folded cascod opamp output stage

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MahmoudHassan

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Hi

I am attaching a photo for a folded cascod opamp for this circuit for example
For M9 and M10 I can add dummies connected to VDD all terminals, also for M3 and M4 but all terminals connected to ground
The problem is in M5 -M6 and also M7-M8 How can I add dummies to these transistors in interdigitated common centroid layout?



Best Regards,
Mahmoud
 

1) Dummies are dead simple when the outer (less
dummies) connection is the natural source supply.

2) Centroid layout is easier when every FET is made
up of 2*N segments, letting you configure placement
such that -every- FET sits on both sides of the
centerline. Like 5/1*2 rather than 10/1.

3) Whether fine-matching the PMOS stack may or may
not be worth the effort, depending on how much front
end gain there is.
 

I would do M7, M8, M9 and M10 as a group with dummies on the outside. Same for M3, M4, M5 M6.
 

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