Does the output of a DAC have quantization noise when outputting a DC voltage value? It seems to me that it will not as long as the DC value does not fall between two output levels of the DAC.

All the information I have been able to find regarding quantization noise of a DAC discusses it in the context of outputting a sawtooth wave or sine wave, and then it ends up being proportional to 1 LSB spread uniformly over the bandwidth of the DAC.


For a DC output, a DAC will not have quantization noise, but it will have quantization error.

EDIT - While noise is technically any unwanted or erroneous component of a signal, in practice it is used to refer to the AC component of such error. For instance, noise is normally characterized as having a spectral density measured in $$\frac{quantity}{sqrt{Hz}}$$ or volts/amps/power/etc divided by the square root of the measurement bandwidth. DC, however, has zero bandwidth, so any such measurement would give an infinite value for DC "noise". As a result, static errors are usually referred simply as errors, or DC errors if context requires. In the case of a DAC with a DC output, the error caused by quantization is called quantization error.

  • \$\begingroup\$ I am not sure I understand the distinction between the two in this context. Could you please elaborate on your response a bit? \$\endgroup\$ – cstraats Jul 30 '15 at 19:36
  • \$\begingroup\$ @cstraats - OK, I've edited. \$\endgroup\$ – WhatRoughBeast Jul 30 '15 at 19:58
  • \$\begingroup\$ Ok, I think I understand now. My interpretation is that the quantization error really only translates into a noise with some spectral density if the output of the DAC is changing (i.e. a voltage ramp or sine wave output), otherwise it is just a DC error. Is that about right? \$\endgroup\$ – cstraats Jul 30 '15 at 20:30
  • \$\begingroup\$ @cstraats -Exactly. \$\endgroup\$ – WhatRoughBeast Jul 30 '15 at 20:54
  • \$\begingroup\$ @cstraats - Well, let me backtrack and explain a little. I was referring to broadband noise as having a spectral density. This does not apply to single-frequency noise. For instance, if a circuit is picking up a pure 60 Hz tone, we would talk about "x volts of 60 Hz noise", rather than referring to spectral density, since a pure tone also has zero bandwidth. But DC is still referred to as error or sometimes offset. \$\endgroup\$ – WhatRoughBeast Jul 30 '15 at 21:32

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