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neoflash Community Fellow Offline Mixed-Signal Designer Posts: 397	hspice model file noise factor Dec 27^th, 2005, 11:37pm My hspice model file does not contain noise parameter: AF KF. However, it specified parameter: noimod=2. When I do simulation of noise, I could see flicker noise. However, I am not sure how simulator knows transisors' noise performance?
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Andrew Beckett

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Re: hspice model file noise factor
Reply #1 - Jan 2^nd, 2006, 10:47pm

You didn't say what model it is you're using. Various models (such as bsim4) have
other parameters for specifying flicker noise. For example in spectre's bsim3v3
implementation:

Code:

Noise model parameters:
196     noimod=1	    Noise model selector.
197     kf=0		  Flicker (1/f) noise coefficient.
198     af=1		  Flicker (1/f) noise exponent.
199     ef=1		  Flicker (1/f) noise frequency exponent.
200     noia=1e20	   Oxide trap density coefficient. Default is 9.9e18 for pmos.
201     noib=5e4	    Oxide trap density coefficient. Default is 2.4e3 for pmos.
202     noic=-1.4e-12     Oxide trap density coefficient. Default is 1.4e-8 for pmos.
203     noid=2e14	   flicker noise subthreshold-above threshold transition coefficient.
204     wnoi=1e-5 m	 Channel width at which noise parameters were extracted.
205     em=4.1e7 V/m	Maximum electric field.
206     flkmod=0	    Flicker noise model (0 for Ids based model, 1 for gm based model).
207     gamma=2.0/3.0     Thermal noise coefficient.
208     nlev=2.0	    49 noise selector.
209     gdsnoi=1.0	  Channel thermal noise coefficient for 49 noise.

Parameters noia,noib,noic etc would also suffice to cause flicker noise.

Check the documentation for the model you're using; there may be different parameters
controlling the noise (bsim4 has this too, for example).

Regards,

Andrew.

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Geoffrey_Coram

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Re: hspice model file noise factor
Reply #2 - Jan 3^rd, 2006, 5:31am

NOIMOD=2 is from BSIM3, and uses with NOIA, NOIB, NOIC.

I find Andrew's post a little misleading:
Quote:

Parameters noia,noib,noic etc would also suffice to cause flicker noise.

If NOIMOD=1 or 4 (or 5), then NOIA, NOIB, NOIC will have no effect at all. If NOIMOD=2 or 3
(or 6), then NOIA, NOIB, NOIC are used, and they have non-zero default values, so you may or may
not find the value in the model card (though the defaults are unlikely to be correct for your process).

(NOIMOD=5 and 6 were added in BSIM3 version 3.3 and make a slight change to the thermal noise model
relative to NOIMOD=1 and 3, respectively.)

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Andrew Beckett Senior Fellow Offline Life, don't talk to me about Life... Posts: 1742 Bracknell, UK	Re: hspice model file noise factor Reply #3 - Jan 3^rd, 2006, 9:27pm Geoffrey is quite right, of course. I wrote my post in a hurry and didn't make it as clear as I should have. Because you'd said that you had noimod=2 in the model file, I'd made some assumptions, but the real point of my post was that flicker noise is not just controlled by kf, af etc. Regards, Andrew.
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