Analog Layout using common centriod technique

[qasmi]

layout of two trnasistors M1 and M2 ,3 fingers each.how can i layout these transistors using common centriod technique?is there any rule in common centriod technique regarding no of fingers of transistor (even or odd no)?

 

[ankitgarg0312]

if possible make 4 fingers instead of 3 fingers and arrange them in below pattern:

ABBA
BAAB

A , B represents fingers of devices..

 

[varunmjman]

U can use this..
ABA
BAB

But always try to make the fingers in multiple of 4. It will make ur design clean and will b more easy to connect and implement the common centroid

 

[ankitgarg0312]

U can use this..
ABA
BAB

But always try to make the fingers in multiple of 4. It will make ur design clean and will b more easy to connect and implement the common centroid

i am not very sure, but this pattern will not be common centroid as there is no common centroid point dividing fingers in two parts..
cross gradients will effect design ....
can you comment on this please??

 

[Saravanan.G]

the odd numbers like 3 are not prefered in common centroid layout.
better to change it to even number.
but if already the finger widths are very minimal.then we try to minimize mismatch to the posible extent but we cannot achieve common centroid.
If the resulting mismatch from layout is minimal then no need to do common centroid layout unless the circuit is very sensitive.
with in a very small area the gradient difference will not be significant
regards
sar

 

[shashikumar.22]

I agree with Saravanan.G,

the odd numbers like 3 are not prefered in common centroid layout.