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Different transistor orientation in different matched MOS array

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Junus2012

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Dear friends,

I completely understand that matched transistor in an array must have the same orientation so my question id different from this case.

it is about if for example we have two indivisual matched MOS array, say array A and array B. in either A or B transistors are matched in the same orientation, but when I want to connect array A with array B I found it better to rotate the array B to match the gap in the layout, thus array B transistors now have different orientaion from A....

Is that ok ?

Thank you in advance
 

If I understood well, you want not only the transistors within the individual arrays to be matched but also the arrays themselves to be matched with each other. Then if this is the case, you better keep them matched, meaning the same orientation.
 
It depends -what- is to be matched.

If you feed array A and array B identical current bias
then they don't care about orientation, local match
is still good and current mirror behavior is fine.

If you feed A and B a master gate bias voltage instead,
you should expect that they do not produce identical
current outputs because the FETs are likely shifted
differently, lithographically (for example gate may be
offset from contact lengthwise for A, widthwise for B,
so A may have more or less source resistance than B).

And you also are depending on ground net integrity,
longitudinal bias from I*R, if you ship voltage rather
than current across any significant distance.

Naturally "same is best". But you can make certain
compromises without much downside, if you make
others appropriately.
 
Dear friends,

thanbk you for your reply

Suppose it is the case of this cascode mirror, I matched M1, M2 in array A and M3, M4 in array B.

According to what I understood from you it is ok for this case as the upper array is depending on the current coming from array A, if it is depending on voltage then it is not that food idea, right ?
 

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