ADC Resolution and Sampling Calculator: LSB Size, Ideal SNR, Nyquist Frequency and Aliasing
Resolution, noise and sampling limits of a converter.
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How this calculator works
Enter the number of bits and the reference voltage.
Enter the sample rate and the signal frequency.
The calculator gives the step size, the ideal SNR, the Nyquist frequency and the aliasing.
Formulas used
- V_{LSB} = \frac{V_{ref}}{2^N}
- SNR = 6.02N + 1.76\ \mathrm{dB}
- f_N = \frac{f_s}{2}
Worked example
With the default numbers in the calculator above:
- Number of levels: 4096
- Size of one step (LSB): 0.805664 mV
- Largest quantisation error (half a step): 0.40283 mV
- Ideal signal-to-noise ratio: 74 dB
- Nyquist frequency (half the sample rate): 24 kHz
- Apparent frequency of the signal after sampling: 18 kHz
Change the numbers in the calculator to see the full working, every step, for your own case.
Common questions
What is the LSB?
The voltage change that moves the converter output by one step. It is the full-scale voltage divided by two to the power of the number of bits.
What is aliasing?
A signal above half the sample rate shows up as a false lower-frequency signal after sampling.
Why is the real SNR lower than the formula?
The formula counts only quantisation noise. Real circuits add thermal noise, jitter and distortion.
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Got a question about this? Ask an engineering question and get a plain-language answer with references.
Further reading: Any electronics or digital signal processing text (sampling and quantisation).
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