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28,304 Views 1 Reply Last post: Nov 5, 2009 1:35 PM by erasto_kashoro RSS
imu Lurker 1 posts since
Nov 5, 2009
Currently Being Moderated

Nov 5, 2009 8:17 AM

Trouble interpretting .noisetran simulation results in eldo

Hi Folks,


Problem statement:

Track and hold Circuit: 1.5v DC ideal voltage source connected to a 1pF capacitor through a CMOS (transmission gate) switch.


Sampling frequency 100nS.


Transient sim run for 50 clock cycles and the average of the hold state noise voltage

taken over these 50 cycles.


Run eldo noisetran statement as follows,


.noisetran fmin=1 fmax=1e9 nbrun=50 nmod=2


(also disabled flicker noise components in my Bsim3v3 model files)


The idea is to observe only the thermal noise.


One would expect the output noise on the capacitor to be
KT/c of 1pF at room temp which would be 64uV or close.


The rms out of the simulator gives me 52uV.


Dosent make sense.


Can anyone who knows how to interpret .noisetran sims comment on this.




erasto_kashoro Lurker 2 posts since
Nov 5, 2009
Currently Being Moderated
Nov 5, 2009 1:35 PM in response to: imu
Re: Trouble interpretting .noisetran simulation results in eldo
Hi Ishwar,
I reviewed your problem statement about Eldo noisetran simulation results not meeting your expectation and I feel there are a number of things about the design and the simulation setup which need to be known before anyone can give helpful comments. I have also discovered from our database that you are a Mentor Graphics customer who has full access to Customer Support, but it seems you have not opened any Service Request to report any problems with our tools. Please note that you can access technical information, documentation, TechNotes and other services 24 hours a day at our SupportNet site:
This site should be your first stop when you have a tool usage problem for which you may want to search for answers from our knowledgebase (or open a new Service Request). I have opened a service request for you (SR 2256090572) so that our engineers in your local area can work with you and resolve the issues you have raised. You will be contacted by someone in you area to discuss the problem and you will possibly be asked to provide a testcase since this is a tricky problem.
Thanks for reporting your problem.
Best regards,

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