how to use 6 bit ADC/DAC to gain 8 bit ADC/DAC performance?

Hi all,

Can anybody suggest some methods of gaining 8-bit ADC/DAC performance with 6 
bit only ADC/DAC?

Any thoughts? Thanks a lot!

at the same sampling rate?

at the same sampling rate?

"kiki" <lunaliu3@yahoo.com> wrote in message 
news:cqtnk1$k7h$1@news.Stanford.EDU...
> Hi all,
>
> Can anybody suggest some methods of gaining 8-bit ADC/DAC performance with 
> 6 bit only ADC/DAC?
>
> Any thoughts? Thanks a lot!
>
>
You could try 4 off 6 bit ADCs or DACS and shift their input/output ranges 
to cover the same range as your 8 bit device?

Best of Luck - Mike

"kiki" <lunaliu3@yahoo.com> writes:

> Hi all,
>
> Can anybody suggest some methods of gaining 8-bit ADC/DAC performance with 6 
> bit only ADC/DAC?

One can use oversampling, or oversampling along with
noise-shaping. The latter technique is commonly called a delta-sigma
(some say sigma-delta, but they're wrong) converter.
-- 
%  Randy Yates                  % "Rollin' and riding and slippin' and
%% Fuquay-Varina, NC            %  sliding, it's magic."
%%% 919-577-9882                %  
%%%% <yates@ieee.org>           % 'Living' Thing', *A New World Record*, ELO
http://home.earthlink.net/~yatescr

balchand wrote:
> at the same sampling rate?

By doing each sample twice? :-)

kiki wrote:
> Hi all,
> 
> Can anybody suggest some methods of gaining 8-bit ADC/DAC performance with 6 
> bit only ADC/DAC?
> 
> Any thoughts? Thanks a lot!
> 
> 
> 

Yes, but in all cases you'll be trading resolution for the need to 
oversample.

I've written an article on extending DAC performance using sigma-delta 
techniques (sorry Randy).  It only presents a first-order modulator, but 
that's worked well for me in the applications where I've used it. 
http://www.wescottdesign.com/articles/sigmadelta.html.

To get more resolution on the ADC side you need to dither the input and 
oversample.  You can either do this with sigma-delta techniques, which 
will require an additional DAC, or you can make an analog ramp or noise 
generator to sum into your incoming signal, which will require a higher 
oversampling rate than sigma-delta.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Tim Wescott <tim@wescottnospamdesign.com> writes:

> sigma-delta techniques (sorry Randy).  

Well, apologize to Inose, Yasuda, and Murakami since these folks were
the originators of the technique [1].  You're also contradicting James
Candy and Max Hauser, per personal conversations with Max Hauser. 

--RY


[1] 
@article{inose,
title = "{A Telemetering System by Code Modulation---Delta-Sigma Modulation}",
author = "{Inose, Yasuda, and Murakami}",
journal = "IRE Transactions on Space Electronics and Telemetry",
year = "1962",
month = "September"}
-- 
Randy Yates
Sony Ericsson Mobile Communications
Research Triangle Park, NC, USA
randy.yates@sonyericsson.com, 919-472-1124

You can use a PGA along with an DAC offset to track the signal if you
are able to oversample it. If the gain saturates then you have to
adjust the DAC offset or zoom out with the PGA.

-Tim

Agreed, the most straight-forward method would be to dither your input
(before sampling) and then oversample the heck out of it.

You can even use a dithering noise diode (from www.noisecom.com)
matched to your ADC to get the proper noise density.