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[FAQ] ADC Noise: How do you calculate the noise bandwidth of your system?

How do you calculate the noise bandwidth of your system when using Delta-Sigma ADCs?

  • If your signal chain has multiple filter components, you must calculate the ENBW for each component by combining all downstream filters in the signal chain. To combine filters, plot them as magnitude (in decibels) vs. frequency and add them point by point.

    For example, to calculate the noise contribution of the amplifier in Figure 4, you would have to combine the amplifier’s bandwidth with the anti-aliasing filter, the ADC’s digital filter and any post-processing filters. You could ignore the electromagnetic interference (EMI) filter in this case since it is upstream relative to the amplifier.

      

    Figure 4: Typical signal chain showing multiple sources of filtering

    Since this can be complicated, read part 5 to learn ENBW approximation methods to simplify your analysis.