Discussion:
[Discuss-gnuradio] speed difference between ADCs and DAC's
Sravya Reddy
2012-05-23 09:41:33 UTC
Permalink
hi everyone,

USRP board has ADC's and DAC's operating with different speeds. why DAC's
are faster than ADC's? please excuse me if it is a basic question.

thanks in advance,
sravya.
Ian Buckley
2012-05-23 15:41:16 UTC
Permalink
ADI tutorial on the topic.
http://www.analog.com/static/imported-files/tutorials/MT-017.pdf
Post by Sravya Reddy
hi everyone,
USRP board has ADC's and DAC's operating with different speeds. why DAC's are faster than ADC's? please excuse me if it is a basic question.
thanks in advance,
sravya.
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wayne roberts
2012-05-27 02:23:06 UTC
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I dont know if that tutorial covers the topic, try this
http://www.analog.com/library/analogDialogue/archives/39-06/Chapter%202%20Sampled%20Data%20Systems%20F.pdf

I think its simple to say why DAC and ADC operate a different speeds.
Its not just speed, also dynamic range (ENOB) is also more difficult to
achieve in ADC.
Ultimately an ADC must guess at what the analog input is due to internal
noises (sample and hold hi-z, etc), which is why the ENOB is always worse
than the number of bits output digitally.

By contrast, the DAC since it operates in reverse, it already knows exactly
what the signal should be, and just needs to switch in the correct resistor
to produce the correct analog value.

A high speed ADC/DAC expert would say this is an over-simplification, but I
only try to convey the basic idea.
Post by Sravya Reddy
hi everyone,
USRP board has ADC's and DAC's operating with different speeds. why DAC's
are faster than ADC's? please excuse me if it is a basic question.
thanks in advance,
sravya.
_______________________________________________
Discuss-gnuradio mailing list
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Ebtisam Ahmed
2012-05-27 06:05:05 UTC
Permalink
Hi all,

Well going into the basics, ADCs have a sample and hold circuits. It
holds the value and sometimes takes the average of some nearby values
and then convert that into digital for precision. While there is no
such thing in DACs; resulting in faster DACs.

Hope this helps..

Regards,
Ebtisam
Post by wayne roberts
I dont know if that tutorial covers the topic, try this
http://www.analog.com/library/analogDialogue/archives/39-06/Chapter%202%20Sampled%20Data%20Systems%20F.pdf
I think its simple to say why DAC and ADC operate a different speeds.
Its not just speed, also dynamic range (ENOB) is also more difficult to
achieve in ADC.
Ultimately an ADC must guess at what the analog input is due to internal
noises (sample and hold hi-z, etc), which is why the ENOB is always worse
than the number of bits output digitally.
By contrast, the DAC since it operates in reverse, it already knows exactly
what the signal should be, and just needs to switch in the correct resistor
to produce the correct analog value.
A high speed ADC/DAC expert would say this is an over-simplification, but I
only try to convey the basic idea.
Post by Sravya Reddy
hi everyone,
USRP board has ADC's and DAC's operating with different speeds. why DAC's
are faster than ADC's? please excuse me if it is a basic question.
thanks in advance,
sravya.
_______________________________________________
Discuss-gnuradio mailing list
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
_______________________________________________
Discuss-gnuradio mailing list
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
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