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Design >> Mixed-Signal Design >> question in opamp design in sigma delta modulator
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Message started by glacieryy on Apr 20^th, 2006, 7:23pm

Title: question in opamp design in sigma delta modulator
Post by glacieryy on Apr 20^th, 2006, 7:23pm

hi all,

i am a beginer in analog ic design and now in my first project sigma-delta ADC.

but,how do i get the specific requirements of opamps (gain,bandwidth,...)in sigma delta modulator?

is there any theory to calculate these parameter?

thanks a lot for your help!!pr

Title: Re: question in opamp design in sigma delta modula
Post by chungmnig on Apr 20^th, 2006, 8:06pm

Matlab is a simple simulation tool.
you can go matlab site to download it.

Title: Re: question in opamp design in sigma delta modula
Post by glacieryy on Apr 20^th, 2006, 8:23pm

thanks for reply!
i have made an ideal modulator ,but i do not know how to get the para for designing a practical opamp!eg.how about the opamp's gain,bandwidth,slew rate?
just by simulation?
thanks for help!!

Title: Re: question in opamp design in sigma delta modula
Post by vivkr on Apr 21^st, 2006, 1:53am

Hi,

You can find information in the yellow book (Schreier, Norsworthy, Temes). I believe that practical issues
of circuit design are discussed in Chapter 11.

A lot also depends on the kind of modulator you have (single-bit, multi-bit, CT, SC, single-loop, MASH etc.).

Regards
Vivek

Title: Re: question in opamp design in sigma delta modula
Post by glacieryy on Apr 22^nd, 2006, 5:59am

Vivek
Thanks for your advice!

please forgive my ignorance,can you tell me how to get the yellow book (Schreier, Norsworthy, Temes)?

my case use multi-bit MASH stucture,discrete time ,SCI.

Thanks again!
Regard!
glacier

Title: Re: question in opamp design in sigma delta modula
Post by vivkr on Apr 23^rd, 2006, 12:43am

Hi Glacier,

I thought it would have been in the "Books" section of this website, but I see that it is not mentioned.
That is a serious omission. Anyway, the book is called "Delta-Sigma Data Converters: Theory, Design, and Simulation".
The authors are Norsworthy, Schreier and Temes. The book is published by IEEE Press. This book has more information
on analog circuit design in Chapter 11 by Brian Brandt, Paul Ferguson and Mike Rebeschini.

The other book is "Understanding Delta-Sigma Converters" by Schreier and Temes, and also by IEEE Press. This is more
for system design.

Unfortunately, both the books are quite expensive. Maybe you can try getting the first one second hand (as it has been around for
a few years) or look in your library.

Other than that, a few tips:

1. The opamp design constraints are similar to those for switched-capacitor filters. So any good text on SC circuits
will be helpful to you in determining noise, bandwidth, gain etc. Try the one by Gregorian and Temes titled
"Analog MOS Integrated Circuits for Signal Processing", again an expensive book and around for a while.

2. As you are designing MASH, you need to be particularly careful of the noise leakage due to the mismatch
between the analog and digital paths which is usually the big issue in MASH. There are several papers on
the subject in IEEE journals with techniques to correct for these. As I have only made single-loop modulators
myself, that is more or less all I can tell you.

Hope that you find this information useful.

Regards
Vivek

Title: Re: question in opamp design in sigma delta modula
Post by glacieryy on Apr 23^rd, 2006, 8:37am

Millions of thanks to Vivek!
What you said benefits me a lot!
I have heard from the two books you mentioned,but I haven't got them yet!Do you have some e-book or pdf version?My email is glacieryy@gmail.com,thanks!

And now ,I really have some SC filter design references,I will study them first!Thanks for your advice!

Thanks again!
regards!
glacier

Title: Re: question in opamp design in sigma delta modula
Post by Ken Kundert on Apr 23^rd, 2006, 9:25am

I have added the yellow book to the Books section (http://www.designers-guide.org/Books/#Norsworthy-1996).

-Ken

Title: Re: question in opamp design in sigma delta modula
Post by glacieryy on Apr 23^rd, 2006, 11:07am

Ken
please forgive my ignorance,I am new in this forum!Do you mean I should buy the book through the website you have sent to me ?Thank you!

regards
glacier

Title: Re: question in opamp design in sigma delta modula
Post by Ken Kundert on Apr 24^th, 2006, 1:01am

Primarily the books given on the site are recommended by the members of the Designer's Guide Community. It is a place to find books on analog, RF and mixed-signal design that other analog designers recommend. If you do go through the links provided on the Books page to either Amazon or Barnes & Noble, then a small percentage of the purchase price comes back to the community and is used to fund the developement or maintenence of the site. So yes, if you are going to buy a book, or actually anything on Amazon or B&N, I would appreciate it if you used the links on the Books page to get there.

-Ken

Title: Re: question in opamp design in sigma delta modula
Post by glacieryy on Apr 24^th, 2006, 5:29am

Thanks Ken!
I think I have gotten what you mean!If I want to read the book,I must buy it!
Thanks a lot!

I also hope someone can give me some suggestions to my case!Thanks for anybody's help!

regard
glacier

Title: Re: question in opamp design in sigma delta modula
Post by Paul on Apr 24^th, 2006, 9:15am

Hi Glacier,

whether you are in industry or academia, you should be able to find some experienced person around you or the university library who has this book available.

As a starting point, you should use Schreier's toolbox, available on the Mathworks web site, to get design parameters for your design:
http://www.mathworks.com/matlabcentral/fileexchange/loadFile.do?objectId=19&objectType=FILE
He's one of the editor's of the above-mentioned book and his toolbox is commonly used in the design of sigma-delta modulators. There are two other toolboxes available, implementing Simulink models, but I never used these, so I cannot comment on their usefulness:
http://www.mathworks.com/matlabcentral/fileexchange/loadFile.do?objectId=2460&objectType=file
http://www.mathworks.com/matlabcentral/fileexchange/loadFile.do?objectId=7589&objectType=file

Paul

Title: Re: question in opamp design in sigma delta modula
Post by glacieryy on Apr 26^th, 2006, 1:31am

hi Paul
Thanks for your advice!
I should have a simulink model first,then use the toolbox to calculate the paraments of the model. Is it right?

Regards
glacier

Title: Re: question in opamp design in sigma delta modula
Post by Paul on Apr 26^th, 2006, 2:55pm

No, Schreier's toolbox uses plain Matlab only. The other two mentioned toolboxes are running in Simulink. If you want to use Schreier's toolbox, you can go straight ahead with Matlab, without having a simulink model. You can first use the basic functions to figure out the main parameters like OSR, number of quantizer bits and modulator order and obtain the resulting performance. You can find some examples here (take care of the line break when pasting the link into your browser):
http://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/E55039C3-3785-4DE4-9926-D87A700DE097/0/guest5.pdf

The toolbox also comes with a short manual describing the different functions.

Paul

Title: Re: question in opamp design in sigma delta modula
Post by glacieryy on Apr 28^th, 2006, 7:53pm

Thanks Paul,
I have download the toolbox and resource.They are very helpful to me .
Thanks again.

Best wishes.
glacier

Title: Re: question in opamp design in sigma delta modula
Post by sheldon on May 6^th, 2006, 7:57pm

Glacier,

Just for completeness, there is also some additional information at:

Sigma-Delta ADC Priciples and Architectures
http://www.imse.cnm.es/esd-msd/WORKSHOPS/MIXMODEST/PRESENTATIONS/LPSDM_Architects_v2.pdf

Errors in Sigma-Delta ADC
http://www.imse.cnm.es/esd-msd/WORKSHOPS/MIXMODEST/PRESENTATIONS/LPSDM_Errors_v2.pdf

Design Example:
http://www.imse.cnm.es/esd-msd/WORKSHOPS/MIXMODEST/PRESENTATIONS/medeiro1_exercise.PDF

In particular, the error presentation discusses the relationship between different design
parameters, for example, open loop gain, and ADC performance.

Best Regards,

Sheldon

Title: Re: question in opamp design in sigma delta modula
Post by glacieryy on May 9^th, 2006, 2:57am

Sheldon ,
Thanks a lot for your help.
These documents are really very useful. :)

Thank you again.

Best wishes.
glacier