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# SNR calculation and ENOB estimation
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*Noise waveform - with no signal attached to the
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input**
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[![](/uploads/27792199e9cffaf0324d9c298038c98a/noise_mini.jpg)](https://www.ohwr.org/project/fmc-adc-100m14b4cha-hw/uploads/77d5dc82b01782ea0d5033e6b887103b/noise.jpg)
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[Document explaining the theory of the
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calculation](https://www.ohwr.org/project/fmc-adc-100m14b4cha-hw/uploads/46560ed82150170e79a691820ba861db/Analog_Devices_MT-003.pdf)
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SNR calculation:
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*SNR = 20** log10( (16384/2/sqrt(2)) / (std(noise\_samples) )\*
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where:
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*16384/2/sqrt(2)** - RMS of the sinewave covering all the dynamic range
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of the ADC
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*std(noise\_samples)** - standard deviation of the noise, which is the
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RMS value of the noise
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*20** log10()\* - for dB calculation
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<table>
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<tbody>
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<tr class="odd">
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<td><strong>Input voltage range</strong></td>
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<td><strong>Standard deviation [bits]</strong></td>
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<td><strong>SNR [dB]</strong></td>
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<td><strong>Estimated ENOB (THD omitted)</strong></td>
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</tr>
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<tr class="even">
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<td>100 mV pp</td>
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<td>2.374</td>
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<td>67.7</td>
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<td>11</td>
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</tr>
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<tr class="odd">
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<td>1 V pp</td>
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<td>1.651</td>
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<td>70.86</td>
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<td>11.5</td>
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</tr>
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<tr class="even">
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<td>10 V pp</td>
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<td>1.421</td>
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<td>72.17</td>
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<td>11.7</td>
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</tr>
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</tbody>
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</table>
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