How do you use "Stick Diagram" in analog layout?

Hi, I`m layout beginner.

I am just about to layout foldedcascode amp., comparator, etc... for the first time in my life.

I ask you about Stick Diagram.
Is that only digital? or can use analog?


and

If all Mosfet`s size is 1u/1u, How do you use layout technique(Multifinger, common-centroid...)? and How do I mathing?

sorry to long question

Re: How do you use "Stick Diagram" in analog layou

yousoo said:

Hi, I`m layout beginner.

I am just about to layout foldedcascode amp., comparator, etc... for the first time in my life.

I ask you about Stick Diagram.
Is that only digital? or can use analog?


and

If all Mosfet`s size is 1u/1u, How do you use layout technique(Multifinger, common-centroid...)? and How do I mathing?

sorry to long question

Click to expand...

hi yousoo

Stick diagrams are useful for beginners as long as the circuit is pretty small like,NAND,NOR,INV etc.. but as the ckt gets pretty complicated involving huge no. of Tx, it is not practical to draw stick diagrams. It gets time consuming.Instead, try and analyse the circuit and plan ur layout accordingly.This again comes from practice.We all learn the same way.
Which technology are you working with?? Coz 1u/1u is already a small sized Tx.Specify the same.
We go for matching techniques like interdigitization/common centroid in analog layouts where matching becomes imp.Common centroid is expected for critical matching , it nullifies the process related gradients in both X and Y axis.
Interdigitization on the otherhand is used where matching required is not very critical , here you have to be careful as it could add parasitic cap(poly to diffusion cap) to your layout in case if large no. of fingers are interdigitized.
You could refer "Art of Analog Layout" by Alan Hastings which will prove to be very useful to u.

regards
Brittoo

Re: How do you use "Stick Diagram" in analog layou

Thank you very much, Brittoo

I use 0.35tech. I make OTA, comparator and counter in 70u × 70u pixel
so, I`m using minimum length and width (1um * 1um) in range guaranteed performance.

and in this situation I thik matcing is critical, but too small size to use common-centroid

plz reply to my question

sorry to bad writing

Re: How do you use "Stick Diagram" in analog layou

Hi yousoo

Since critical matching is expected, just see if common centroid matching is possible. This would provide symmetry along X axis as well as Y axis. Add dummies to the actual tx to be matchjed at the edges which will ensure poly matching.Also, try and see if dummies can share the diffusion to ensure that the actuall Tx see the same environment on both the sides.if you hav to match 2 Tx , then you could try ABBA pattern reversing the same on the next row. Add guard rings to the figure, follow identical routing as much as possible.Place the i/ps as close as possible. Even identical contacts placement has to be followed as much as possible.
As far as .35u technology is concerned, you can very well go ahead with Common centroid as it doesn`t matter. Common centroid is followed in 180n,90n technology which are far smaller than the former.

Warm regards
Brittoo