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Modeling >> Behavioral Models >> noise model of ota
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Message started by parthsv on Jan 14^th, 2007, 8:47am

Title: noise model of ota
Post by parthsv on Jan 14^th, 2007, 8:47am

Hi All,
I am building a pipeline ADC and in order to verify certain aspects of the ADC i have built a verilogA model of the ADC. I need to incorporate thermal noise of the opamp/comparator of each stage of pipeline and I am new to noise modelling in verilogA. Can anyone here please give me directions on how to proceed in verilogA?
Thanks in Advance.

Title: Re: noise model of ota
Post by Geoffrey_Coram on Jan 15^th, 2007, 5:19am

Are you planning to run a noise/pnoise simulation (in which case you can use white_noise()), or do you need to implement something that will work in a transient analysis?

Title: Re: noise model of ota
Post by parthsv on Jan 15^th, 2007, 9:46pm

Hi,
Thanks for your respone. I need to include thermal noise in transient analysis.

Title: Re: noise model of ota
Post by Visjnoe on Jan 16^th, 2007, 12:45am

Dear parthsv,

To include thermal (white noise) into your transient simulation, you have several options:

1. If you have access to ELDO, you can include noise sources (ELDO primitives) into your schematics.
They will inject noise during transient analysis.

2. Otherwise, generate a random number stream (using MATLAB or an AHDL) and include this into your
simulation. Make sure that you control the noise power well in this case by using a fixed time step!
If you want 'shaped' (e.g. 1/f) noise, pass the random number stream through a digital filter.

Kind Regards

Peter

Title: Re: noise model of ota
Post by parthsv on Jan 16^th, 2007, 5:30am

Hi Visjnoe,
I already have actual noise numbers(rms voltage/power) per stage from the circuit simulation. Is there a way to include these numbers in the simulation setup?

Title: Re: noise model of ota
Post by Geoffrey_Coram on Jan 16^th, 2007, 6:24am

parthsv wrote on Jan 16^th, 2007, 5:30am:

Hi Visjnoe,
I already have actual noise numbers(rms voltage/power) per stage from the circuit simulation. Is there a way to include these numbers in the simulation setup?

The rms voltage should be used to set the scaling for the random number generator, but since you're doing transient, you still need to generate the random numbers!

Title: Re: noise model of ota
Post by Andrew Beckett on Jan 17^th, 2007, 3:09am

Note that if you include noise using the usual verilog-a noise functions, then that noise will be included in a spectre transient noise simulation. Of course, you'll get the noise from all the devices in the circuit too - so if you only want to include the noise from this model, then you'd have to use the random number generator approach that others have suggested in this thread.

Regards,

Andrew.