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Matching consideration of MOSFET_C filter

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Dear friends,

Here I am showing an example of 2nd order MOS-C filter,

fill.PNG


Should I match the componets (C and G transistors ) ? means do I neéd to intedegitize them ? or only need to put them near
What is the best plan for matching the feedback elements in this circuit

Thank you
 

You cannot Inter-digitize them because you're working on a Differential System, otherwise you disturb the Balance..
Instead, you should use dummies around them.
 
Hello

Regardless this circuit, how it is possible not to match the two feedbacks (from positive and negative outputs )of the fully differential amplifier circuits,
if so then the two feedbackls will suffer mismatching and we lose the concept of the fully differential amplifier.
 

You match them by creating layout for one half of the differential circuit and create a mirror symmetry for the other. They are not interdigitated but still matched. If you interdigitate, you will create capacitive coupling between the two halfs which may alter our filter response.
 
A good matching would also require to match the parasitics (R and C).

Note that when you have mirror symmetry in the layout, and know, form symmetry considerations, that the two halves are perfectly matched, the parasitic extraction tools may still generate different RC networks for parasitics (because extraction tools have a built-in "anisotropy"), so you may see a mismatch that is an extraction/simulation artifact.

Very often, though, creating a perfectly mirror symmetry is difficult or impossible, so one should take care in evaluating a systematic mismatch caused by parasitics.
 
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