Sigma-delta ADC - Electronic Circuits Projects Diagrams Free

aiva · 13th December 2005, 10:39 AM

Does anybody know how programmable amplifier in sigma delta ADC functions and how its gain influences on measurement accuracy

**Nigel Goodwin** · 13th December 2005, 10:53 AM

Have you considered using google?, a simple search finds a great deal of information, including this one:

http://www.maxim-ic.com/appnotes.cfm...te_number/1870.

aiva · 13th December 2005, 12:19 PM

But there is no any description of PGA !!!

Oznog · 13th December 2005, 06:09 PM

The spec will tell you how the PGA will affect its accuracy. Without a spec we'd just be making up numbers and it's pointless.

Sigma-delta ADCs that I know have increasing offset errors if the source impedance is not low. Works great with low impedance shunts. On the other hand the output impedance of say a Pi-filter or a microphone may be a problem, in which case an amplifier is necessary. Programmable gain may or may not be helpful.

aiva · 14th December 2005, 07:55 AM

Thank you for reply.

Quote:

Originally Posted by Oznog

Sigma-delta ADCs ... have increasing offset errors if the source impedance is not low...
Programmable gain may or may not be helpful.

This information is very interesting since it confirms my preliminary hypothesis, that amplification in such amplifiers is made by change of frequency. Otherwise I can't to explain so strange sequence of amplification factors (1, 2, 4, 8, 16...).
But where it has been written for sure???

Am I right? How do you think?

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

13th December 2005, 10:39 AM	#1
aiva	Sigma-delta ADC Does anybody know how programmable amplifier in sigma delta ADC functions and how its gain influences on measurement accuracy

13th December 2005, 10:53 AM	#2
Nigel Goodwin	Have you considered using google?, a simple search finds a great deal of information, including this one: http://www.maxim-ic.com/appnotes.cfm...te_number/1870. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

13th December 2005, 12:19 PM	#3
aiva	Thanks But there is no any description of PGA !!!

13th December 2005, 06:09 PM	#4
Oznog	The spec will tell you how the PGA will affect its accuracy. Without a spec we'd just be making up numbers and it's pointless. Sigma-delta ADCs that I know have increasing offset errors if the source impedance is not low. Works great with low impedance shunts. On the other hand the output impedance of say a Pi-filter or a microphone may be a problem, in which case an amplifier is necessary. Programmable gain may or may not be helpful. __________________ I thought what I'd do was I'd pretend I was one of those deaf-mutes.