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I know that the opposite is possible i.e. using 2 DAC's to get a higher quality output, but is it possible with ADC's?

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  • \$\begingroup\$ And your premise isn't correct either; you can't combine two DACs to double their resolution. \$\endgroup\$ – duskwuff -inactive- May 8 '17 at 22:52
  • \$\begingroup\$ @duskwuff If you check Microchip mcp4822 there is documented an application to get a 24-bit DAC by combining 2 12-bit channels of a DC. \$\endgroup\$ – John Am May 8 '17 at 23:04
  • \$\begingroup\$ To do that with DAC or with ADCs requires that the device dealing with the most significant bits has an accuracy equal to of the LSB of the whole system - most ADC/DAC only have an accuracy of about 1LSB or slightly better referenced to its own bit length. \$\endgroup\$ – Kevin White May 8 '17 at 23:45
  • \$\begingroup\$ I assume you are talking about ww1.microchip.com/downloads/en/DeviceDoc/20002249B.pdf That is not what you call a well-thought-out app note. The specification of "a digital value in the range 0-4096" ought to be a tipoff. What the app note fails to mention is that the two resistors must have a resistance ratio accurate to the unit DAC dynamic range. So, even for the 1000:1 ratio implied, this means resistors matched to 0.1%, and a full 24-bit unit would require matching to 0.024%. Worse, the interpolation is not consistent, but varies with the level of the major DAC. \$\endgroup\$ – WhatRoughBeast May 9 '17 at 3:01
  • \$\begingroup\$ your error should go down by one lsb, but double rez? nope... \$\endgroup\$ – dandavis May 9 '17 at 3:31
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I know that the opposite is possible i.e. using 2 DAC's to get a higher quality output, but is it possible with ADC's?

generally no.

that means in some cases it is doable. For example, for adc's with external reference.

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