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Design >> Analog Design >> Does the length of mos can exceed the upper limit in PDK?
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Message started by xianweng on Aug 8^th, 2013, 8:40am

Title: Does the length of mos can exceed the upper limit in PDK?
Post by xianweng on Aug 8^th, 2013, 8:40am

Hi,all
Does the length of mos can exceed the upper limit in PDK? For example,if the max length of mos is 10u in PDK.Does the length of mos can exceed it just as a capacitance for filter purpose ?

Thanks any help in advance

Title: Re: Does the length of mos can exceed the upper limit in PDK?
Post by boe on Aug 9^th, 2013, 1:35am

Hi xianweng,
what does the DRM say?
- B O E

Title: Re: Does the length of mos can exceed the upper limit in PDK?
Post by xianweng on Aug 9^th, 2013, 4:26am

who is DRM

Title: Re: Does the length of mos can exceed the upper limit in PDK?
Post by Kevin Aylward on Aug 9^th, 2013, 7:40am

Usually the limit is set to those allowed by the Design Rules of the process. A waiver may be available at your own risk. For a capacitor, just use more devices in parallel. For use as a long mosfet, use several in series with their gates tied together.

Title: Re: Does the length of mos can exceed the upper limit in PDK?
Post by boe on Aug 9^th, 2013, 12:12pm

@xianweng: DRM = Design Rule Manual.
@Kevin Aylward: Sound advice.
- B O E

Title: Re: Does the length of mos can exceed the upper limit in PDK?
Post by xianweng on Aug 10^th, 2013, 3:32am

Kevin Aylward wrote on Aug 9^th, 2013, 7:40am:

Kevin_Aylward ,thank you for your reply.
We want to change technology of a chip that layout were already done .In that version ,some length of decouple capacitance (mos as capacitance)exceed the new pdk's limit.

In design rule,it just say the min length of mos,but do not say the max,so I think i will be ok if L exceed the pdk limit just as capacitance

Title: Re: Does the length of mos can exceed the upper limit in PDK?
Post by xianweng on Aug 10^th, 2013, 3:33am

boe wrote on Aug 9^th, 2013, 12:12pm:

@xianweng: DRM = Design Rule Manual.
@Kevin Aylward: Sound advice.
- B O E

B O E,thank you for your reply
In design rule,it just say the min length of mos,but do not say the max,so I think i will be ok if L exceed the pdk limit just as capacitance

Title: Re: Does the length of mos can exceed the upper limit in PDK?
Post by avlsi on Aug 15^th, 2013, 8:04am

If you want higher Length permitted than PDK. Just stack the transistors!!!