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loose-electron

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Re: Is this a good way to place dummy transistors
Reply #15 - Oct 05^th, 2007, 4:29pm

A 7 GHz ring oscillator?

Instead of obsessing on matching, why dont you AC couple each stage so that matching offset is a non issue? Need to have a startup circuti on the ring, but thats ok.

Or, if you are only coming off one stage of the ring, then matching is a non-issue -

At 7GHz you want minimal parasitics.
Jerry

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Jerry Twomey
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Berti

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Re: Is this a good way to place dummy transistors
Reply #16 - Oct 7^th, 2007, 10:25pm

Hi all,

back to layout Wink

Assuming I use a multi-finger layout sharing source/drain with enough dummies at each side. How do I tell that to the BSIM model?
I think the BSIM model just calculates the vth-shift depending on the number of finger of each device. Or do you use post-layout
simulations?

Regards

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carlgrace

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Berkeley, CA

Re: Is this a good way to place dummy transistors
Reply #17 - Oct 17^th, 2007, 10:24am

Berti,

Sorry for the late reply. You tell BSIM model about your dummies by increasing the SA and SB parameters in the model. They default to minimum for the process, which is the maximum stress condition. If you put SA=3.0u and SB=3.0u into your model cards, you will be able to simulate without layout extraction of the STI effect.

Carl

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Berti Community Fellow Offline Posts: 356	Re: Is this a good way to place dummy transistors Reply #18 - Oct 17^th, 2007, 10:21pm Thank you Carl. I found the parameters.
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jimwest Junior Member Offline Posts: 26	Re: Is this a good way to place dummy transistors Reply #19 - Oct 19^th, 2007, 6:53pm To Carl, Is there any reason to set SA=3.0u and SB=3.0u ? How about 4.0u or 5.0u? And is 3.0u a universal rule for all the process less than 0.13u? Finally does the BSIM4 contain the STI effect, cuz I found the relevant model in the PDK? Kinda Regards, Jim
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