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Help me with transistors matching

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s3034585

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Help in matching

hi
i am designing layout for bias circuit. in that i have 4 pmos trans.. with a finger size of 10 each. there sournce are connected to a common source and the drain is connected to dif pins.
now i want to match theses transistor. the size is as follows
w = 50 u
l = 5u
fw =5 u
nf =10
count = 1
slice = 1.
as you can see the size and the no of fingers is 10 hence it will consume large
space if i keep them in series.

can any one tell me how to break them into more slices. because even though the fingers are 10 they are all in 1 slice hence cant be separted.

thanks in advance
tama
 

Help in matching

fw=12.5
nf=4
 

Help in matching

hi
can u explain what is slice,count and difference between slice and fingers
 

Re: Help in matching

Well, better way is to use common centroid topology.Follow this configuration:

Recognize the diode fet. You have to have this on the center of the topology.Say this one is M0, and M1,M2,M3,M4 are following. If you have differential input, you have to match also the differential input bias .Say this is M1 and M3

As you have ten fingures each, you will have in total 20 on top and 20 on bottom, all algned symetrical on the y and the x axis and all put in series that is : sM1dM1sM2dM2sM3dM3s.....

On the bottom right and on the top left of the center, next to sM0dM0s put the pair :

sM1dM1sM0dM0sM3dM3d
sM3dM3sM0dM0sM1dM1s

Now build up next to this center. Use the M2 ( say bias of differential pair) in cross topology, then M4, then M1 and M3 again ans o on.

It worked for me! You save space, you have less wiring, you manage to have all of them very well matchedas, a degradetion from left to right will be distributed to all fets and it will be canceled, and you will have a nice design. Place it benith the main pair and vouala! you have it ready
D
 

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