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Simulators >> Circuit Simulators >> How to calculate k'=u*cox value in mos?
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Message started by hande.vinayak on Apr 19^th, 2007, 7:50am

Title: How to calculate k'=u*cox value in mos?
Post by hande.vinayak on Apr 19^th, 2007, 7:50am

Hi to all,
Can anybody tell me, how to calculate k'=u*cox value in mos?
I am using TSMC 90 nm PDK.I am working on cadence spectre for simulation.
Plz,do the needful.
Thnx,

Title: Re: How to calculate k'=u*cox value in mos?
Post by ywguo on Apr 20^th, 2007, 7:14am

Hi, hande,

I have tried to simulate the I/V curve and extract the K' value. It is impossible to calculate K' value from the model parameter because of the complexity of notorious BSIM3 model.

Thanks
Yawei

Title: Re: How to calculate k'=u*cox value in mos?
Post by Mobeedikk on Apr 20^th, 2007, 9:00am

What I usually do is get a representative W/L of the type of transistor I'd use, then
extract Vth by:
1. plotting Ids vs Vgs with Vds at some small voltage (~50mV is typical).
2. take the derivative of this to get gm
3. find the Vgs that corresponds to the maximum gm
4. linearize the Ids vs Vgs curve around this Vgs point, and extrapolate back to the x axis. This will give you Vth
I then plot out an Ids vs Vds curve, and do a least squares fit of the equations to the IV curve to find k'. If you're using square law, fit the square law equation to the IV curve. If you're using Rabaey's velocity saturation equation, fit that equation to the IV curve.

Title: Re: How to calculate k'=u*cox value in mos?
Post by Geoffrey_Coram on Apr 23^rd, 2007, 4:17am

Hmm .. I thought there was a "ueff" output parameter, but I don't see it. There is a betaeff in Spectre, which ought to be ueff * Cox * Weff / Leff. Can you use that?