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Layout of fully differential filter circuit with matching

Junus2012

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Dear friends,

in the image below is a circuit of fully differential filter.

filterlayout.PNG


How to match the feedback elements in the layout design so that R becomes equal in every element, same for C1, C2, C3.
How to match the MOS transistors?

I would appreciate your help
Thank you in advance
Best Regards
 

jgk2004

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Hi there,
So to start, all your R's should be in the same orientation. No rotations. Also, they should be the same Width. If you can make them all segments of each other that helps as well. As for C's, same orientation as well. Also, maybe you can make multiplies. As for transistors, is this high speed or low speed accurate. If your high speed, things are normally small and cross quads/common cent will add to much cap and kill you. Here since things are small its best to put side by side. If its slow, follow normal techniques like common cent/cross quads.

Hope is helps,
JGK
 

bkdraster

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The crucial thing is to make Vin and Vip lines symmetric, including resistor,switches and caps. Vcm has to be as closest as possible as well. I suggest you to use unit size for all resistors and scale them with m parameters. Same for caps and switches as well. Inside the OPAMP, the most crucial part is to match differential pair. The rest depends on the topology of OPAMP.
 

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