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Design >> Analog Design >> how miminum length should I used?
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Message started by Robert on May 31^st, 2007, 3:03am

Title: how miminum length should I used?
Post by Robert on May 31^st, 2007, 3:03am

hi, all!
i am designing a folded cascode OTA used in a LDO, to achive a acceptable offset caused by the transistor's mismatch, how miminum length of the input and load transistors should I used, my design is based on the Charter 0.35um CMOS process. please give me any suggestions from your tapeout experience, thanks a lot!

best regards,
Robert

Title: Re: how miminum length should I used?
Post by krishnap on May 31^st, 2007, 3:44am

Hi Robert,

Usual practise is to keep minimum design length to be 2 to 3 times that of process node.
In this case 2-3*0.35um

Regards,
Krishna

Title: Re: how miminum length should I used?
Post by Berti on Jun 4^th, 2007, 12:20am

Hello Robert,

I think this depends on the offset you can tolerate.
For applications where offset isn't the major concern, but
speed is important I usually use minimum length transistors
to take full advantage of the technology.

If offset is important but speed moderate I agree with Krishna
not to use minimum design length.

Cheers,

Thomas