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bakaberry
Joined: 06 Feb 2009
Posts: 4
Helped: 1
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 02 Jul 2009 19:41 matching mosfets |
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Hi I'm pretty new to rf layout and am unsure how to layout 4 matching mosfets for my vco design. The thing is these mosfets don't share a common drain or source, so those common centroid patterns like ababbaba etc. doesn't seem to work in my mind. The mosfets are paired of however and the gates of the pairs are connected together. I've looked through two textbooks and a bunch of websites and couldn't find any examples of this. I was wondering if anyone has an example of how they laid this type of thing out, a screen shot would be helpful too.
Maybe common centroid is not suitable for this? should i just place the four mosfets close together without interdigitzing or common centroid?
thanks
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deepak242003
Joined: 24 Dec 2008
Posts: 190
Helped: 10
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03 Jul 2009 4:48 mosfet matching common centroid |
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| In this case, we can arrange in centroid pattern without sharring also.. same we do for process <90nm to eliminate LOD effect.... so if the processs is <90nm you can arrange the transistor in common centroid fashion (without sharing any source or drain) and then surround each transistor wiht dummy transistor of minimum gate lenght...
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03 Jul 2009 4:48 Ads |
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bakaberry
Joined: 06 Feb 2009
Posts: 4
Helped: 1
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03 Jul 2009 8:05 common mosfets |
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| thanks for the response deepak, im my case I'm using 0.13um process. Would I be able to just group say a couple fingers of the same mosfet surrounded by a dummy and just lay those out in common centroid fastion with adjacent groups not sharing source/drains?
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deepak242003
Joined: 24 Dec 2008
Posts: 190
Helped: 10
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03 Jul 2009 9:14 matchun mosfets |
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| I suppose that is only thing you can do.. more over you can take care of other conditions like surronding,no power or other routing going over them, using same metal layer and lenght for connecting these devices.......
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