cross-coupled common centroid transistors layout matching

[Junus2012]

Dear friends

I need your urgent help in the layout design issue, I have told before that this the first time to deal with this topic

I want to match three transistors (A,B,C) each one has 6 fingers (m=6). please consider m is fixed (I can not change it)
before you suggest me i will give you my idea

the actual number of transistors are 3*6=18. to put this in a square array, we have to extend it to 25 transistors by putting 7 dummy transistors, any way I even dont know how to arrange them


please, if you have any idea i would appreciate it

another question, is it mandatory for the cross coupled arrangement to be a square array?

thank you once again,

 

[jirika]

I don't think you need a square shape.
I would do it this way. A,B,C are transistors and D is dummy.

 

[Junus2012]

thank you Jirika

Now please help with the next one

two transistors (A,B), B is five times larger than A. How you will manage that ??? please i need your help

 

[jirika]

Heh that's not good
You can effectively match only transistors with the same size or at least very similar. Anything else just place not far from each other.
If you have the same transistors (same size) great you can do what I shown. But if one of them is 5x large then it's useless. Just keep them together and keep their gate in the same direction.

 

[Junus2012]

hello jirika

actually this ratio I need because it is a part of a current mirror and I must afford this ratio so what it must be like that.

I am making the unit size is equal but transistor B with 5 fingers, so what you say now???

 

[jirika]

Oh sorry I thought that the difference is in length not in width. OK that's not bad after all
What about this? I'm treating with B as 5 times more than A or C. A-6pcs, B-30pcs and C-6pcs.

 

[Junus2012]

hello Jerika

for the second problem I only have two transistors (A,B). the one with three transistors is solved
can you please repeat your suggestion with only two transistors

 

[jirika]

Sorry senan, I don't understand it well.
Please specify which transistors you have (A, B, C ...) and specify their number.

 

[Junus2012]

Hello jiriKa

forget the one with three transistors, consider that I have only two transistors (A,B). the transistor B is five times larger than A. it mean that B have m=5 and A have m=1.

or you can make A with m=2 and B with M=10 . or what ever you suggest

Thank you

Sorry senan, I don't understand it well.
Please specify which transistors you have (A, B, C ...) and specify their number.

 

[jirika]

Well If you can split them you can have something like this (B-10pcs, A-2pcs, D as dummy-4pcs):

 

[Junus2012]

What about if i dont use the dummies and make like

B B B
B A B
B A B
B B B

 

[arun2011]

for your 1st questn i would suggest the following pattern
ABCCBA
CABBAC
ABCCBA

for 2nd questn watevr you suggested is fine......