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daisy Junior Member Offline Posts: 17	how can I see the 1/f noise in Cadence Jun 25^th, 2008, 12:12am Hi! I am simulating the noise in cadence,I have used the .scs file containing the 1/f noise parameters like noimod,kf,af and ef.However,in the noise summary's results display window,the results don't contain the 1/f noise value.How can I see the 1/f noise contribution in the window? Any suggestion woule be helpful!
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HdrChopper

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Re: how can I see the 1/f noise in Cadence
Reply #1 - Jun 25^th, 2008, 8:15pm

Hi daisy,

If you ask for spot noise results, the only way to see 1/f contribution is to ask for spot noise at several different increasing frequencies (starting from very low frequency values) and see how such spot noise decreases at -10dB/dec.
If you ask for integrated noise you could ask for such noise but integrated in decades: for example, ask for integrated noise from 10HZ to 100HZ, then from 100Hz to 1KHz and so on. You should see same decrease rate on the noise power as you move from one decade to the next one.

Finally, Have you tried plotting the noise instead of just looking at the noise summary results? Right there the 1/f noise profile should be evident.

Hope this helps
Tosei

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daisy

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Re: how can I see the 1/f noise in Cadence
Reply #2 - Jun 25^th, 2008, 9:34pm

Hi Tosei
Thank you for your answer!I'm not sure whether I can understand it like this:we can't see the 1/f contribution directly in the results window,namely,we can't get the value called fn in the table like id,rd and rs,and we can only compare the values at different frequencies to find the contribution of the 1/f noise?However,as seen in the picture snap1,the total noise value equals the id noise value,does it mean that the total noise does not contain the 1/f noise?
I have plotted the noise,and as what you said,I can see the 1/f noise in the low frequency if I add specific frequency points,which are plotted in picture snap2,3.Or else,the curve will be flat in the low frequency domain like picture snap4.

Thank you for your suggestion!
daisy

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Snap1_002.jpg

« Last Edit: Jun 26^th, 2008, 12:09am by daisy »

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daisy Junior Member Offline Posts: 17	Re: how can I see the 1/f noise in Cadence Reply #3 - Jun 26^th, 2008, 12:13am I add some specific points like picture snap3,and we can see the 1/f noise character in the plot.
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daisy Junior Member Offline Posts: 17	Re: how can I see the 1/f noise in Cadence Reply #4 - Jun 26^th, 2008, 12:17am snap3
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daisy Junior Member Offline Posts: 17	Re: how can I see the 1/f noise in Cadence Reply #5 - Jun 26^th, 2008, 12:18am snap4 I don't select the "add specific points" button,and the low frequency domain in the plot is flat.
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HdrChopper

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Re: how can I see the 1/f noise in Cadence
Reply #6 - Jun 26^th, 2008, 6:59pm

daisy wrote on Jun 25^th, 2008, 9:34pm:

we can't see the 1/f contribution directly in the results window,namely,we can't get the value called fn in the table like id,rd and rs,and we can only compare the values at different frequencies to find the contribution of the 1/f noise?However,as seen in the picture snap1,the total noise value equals the id noise value,does it mean that the total noise does not contain the 1/f noise?

Hi daisy,

The 1/f contribution is included in id, and therefore it is also included in the total noise (rd and rs do not contribute with any 1/f component). Since you are covering the low frequency range in the noise analysis the total 1/f power is way much larger than the white noise contributors (rd and rs). Consequently the addition of them to id (which contains 1/f contribution) virtually does not change the final total noise value.
The fact that you were not including the specific point, hid the 1/f contribution in the plot since you basically skipped all the 1/f region since the freq step size was set to automatic. Adding those low frequency points let you see the 1/f profile.

Regards
Tosei

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daisy

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Re: how can I see the 1/f noise in Cadence
Reply #7 - Jun 26^th, 2008, 7:27pm

Hi Tosei!
Thank you for your explanation!I've learned a lot.I still have a question.In hspice,the id noise means the output channel thermal noise,and the flicker noise is presented by fn.So,do you mean that in cadence spectre,the id contain the channel thermal noise and the flicker noise?If it is,how can I separate them?

Thanks a lot!
daisy

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Geoffrey_Coram

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Re: how can I see the 1/f noise in Cadence
Reply #8 - Jul 1^st, 2008, 5:24am

I'm surprised that you don't get a separate fn entry for your MOS devices. Are you using bsim3v3 or bsim4? (I assume so, based on your comments about NOIMOD.)

I see many more noise components for my BSIM4 device (fn and also igb, igd, igs for shot noise of the gate leakage currents, etc.).

When I tried bsim3v3, I got an entry for "fn" only when there was non-zero flicker noise; perhaps you need to check your modelcard for correct parameters. Check not only NOIMOD but also FLKMOD and NLEV.

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daisy

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Re: how can I see the 1/f noise in Cadence
Reply #9 - Jul 2^nd, 2008, 12:00am

Hi Geoffrey_Coram
� �Yes,I am using bsim3v3.I have checked the .scs file and I haven't found any parameter called flkmod or nlev.Before simulating,I only add four parameters--noimod,kf,af,ef,both for nmos and pmos,into the model .scs file.Anything else needs to be done to complete the noise simulation correctly?Can you describe the steps you do to complete the noise simulation?

I appreciate your help!
daisy

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Geoffrey_Coram

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Re: how can I see the 1/f noise in Cadence
Reply #10 - Jul 3^rd, 2008, 4:54am

Here's a test file I used and got 'fn' in wavescan. I don't use ADE, so I don't know about the noise summary window.

*
m1 (d 0 0 0) nch l=10u w=10u ad=10p as=12p pd=12u ps=12u nrd=3 nrs=3
model nch bsim3v3 js=1n jsw=1p rsh=0.1 kf=0.1
v1 (d 0) vsource dc=1
h1 (nout 0) ccvs probe=v1 rm=1
noi1 (nout 0) noise start=1 stop=1e3 dec=10

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Geoffrey_Coram Senior Fellow Offline Posts: 1998 Massachusetts, USA	Re: how can I see the 1/f noise in Cadence Reply #11 - Jul 3^rd, 2008, 4:57am Another thing to check: are you sure you added the parameters to the right model card? If there are several models, maybe you're simulating a different bin (lmin/lmax). Try adding a bogus parameter like "daisy=123" and see if the log file reports that it's ignoring that parameter.
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daisy

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Re: how can I see the 1/f noise in Cadence
Reply #12 - Jul 5^th, 2008, 2:04am

Hi Geoffrey_Coram
Thank you for your help.
I'm sure that the parameters are added correctly.And I still have some questions about your test file.
I saw in the manual that the sequence is D,G,S,B,so in "m1 (d 0 0 0)",does it mean that the gate is connected to ground? and whether the v1 is connected to the drain of m1?I'm still puzzled about the h1 and noi1,which nodes are they connected to ?

Thank you for your explanation!
daisy

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Geoffrey_Coram

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Re: how can I see the 1/f noise in Cadence
Reply #13 - Jul 7^th, 2008, 4:53am

Yes, I did ground the gate; there is still some leakage current, and any non-zero Id will generate flicker noise.

I used the h-element to measure the drain current and convert it to a voltage; typing this now, I recall that Spectre's noise analysis has some option to measure output current noise directly.

noi1 is the name of the noise analysis; I'm measuring the voltage noise on "nout"

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daisy

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Re: how can I see the 1/f noise in Cadence
Reply #14 - Jul 18^th, 2008, 2:01am

Thank you for your help!I will have a try.
daisy
Geoffrey_Coram wrote on Jul 7^th, 2008, 4:53am:

Yes, I did ground the gate; there is still some leakage current, and any non-zero Id will generate flicker noise.

I used the h-element to measure the drain current and convert it to a voltage; typing this now, I recall that Spectre's noise analysis has some option to measure output current noise directly.

noi1 is the name of the noise analysis; I'm measuring the voltage noise on "nout"

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