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28,028 Views 1 Reply Last post: Dec 30, 2009 6:01 PM by erasto_kashoro RSS
ashutoshdeenanath Lurker 1 posts since
Dec 22, 2009
Currently Being Moderated

Dec 22, 2009 9:22 AM

.noisetran

Hi

 

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.

 

Thanks,

ashu

erasto_kashoro Lurker 2 posts since
Nov 5, 2009
Currently Being Moderated
Dec 30, 2009 6:01 PM in response to: ashutoshdeenanath
Re: .noisetran

This looks like the same issue raised several weeks ago under the title "Trouble  interpreting .noisetran simulation results in eldo", and was posted at:

    http://communities.mentor.com/mgcx/message/9988#9988

It is advisable to review the problem statement and response(s) in that link to see if they apply to this ".noisetran" simulation issue.  Please provide additional information on the simulation setup including at least parts of the netlist so that readers may understand the design contribute more meaningful comments.

 

Thanks, Erasto.

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