how to put dummy transistors for input pair?

[Robertt]

I am doing the layout of a differential amplifier and considering put dummy transistors for the input pair which needs good matching.

How to deal with the dummy transistors? leave the Drain, Gate, Source open? I think dummy transistors will share drain or source with the input pairs. how to deal with the other two ends?

 

[noiseless]

check book " the art of layout"

 

[arpit_655]

u shud ensure the same surrounding environment for perfect matching....
refer to "CMOS analog IC design" by B.Razavi

 

[xiongshoufen]

you should make the dummy transistor off, or waste power!!!

 

[franck]

Hi,

You don't really need dummies on a diff pair as long as you are doing a common centroid layout.

Franck.

 

[Robertt]

Can I leave the dummy open? that means dont connect the ends of the dummy transistors? or just connect some ends and leave other ends open?

one more question:

I put dummy resistors surrounded by nwell which connected to VDD. I connect to ends of dummy resistors to VDD but cound't pass the Extract. It showed there were errors. After I disconnected the ends of dummy with VDD, the errors disappeared. That means leave the dummy resistor open. Is that ok?

 

[qutang]

I think open drain is not a good idea.