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Optimum strategy to layout MOSFET cascoded mirror

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Junus2012

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Hello,

in the image down is the known wide swing mirror.

casceeeee.jpg

Kindly I need your discussion about layout this circuit.

1. I have two approaches, in the first one I would layout M1 and M2 seperately from M3 and M4 then I connect the two matched array

in the second approach, I would layout M1, M2, M3 and M4 in one matched array, but this is making the connection more complex.

Therefore I need please your opinion about it, which one of the approaches should be better.

2. the diode connected transistor M5 is actullay located in the biasing circuit from this mirror, should be a problem ?

3 . I am usually matching my arrays in one row like for example ABBA or in two rows like ABBA/BAAB, I never go to higher diamentions like four rows althaugh it is supposed to give better matching but the complexity of connection and te parasatic associated to it will be also high, what you think ?

Thank you in advance
 

1. first approach is pretty good, I suggest it. Match mirrors and cascode devices separately is more effective. Cascodes and mirrors are not the same size usually, why would you match them together? I know it is possible, sometimes easier, not the worst.
2. not a problem, but if bias is too far it is not recommended. In IC design the usual way is to deliver bias current rather than voltage, not just because it is possible, it is better to avoid different ground offsets/voltage steps.
3. it depends on accuracy or bandwidth is more important, you have just answered this with your question
 
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