Spurious-Free Dynamic Range
SFDR = 20 · log10(Vsignal / Vspur)
Quick answer
This calculator solves SFDR = 20 × log10(Vsignal / Vspur) for SFDR. With Signal Amplitude 12 V, Worst Spur Amplitude 0.6 V, the result is 26.02 dB. It solves in 3 directions, so you can enter the values you have and get the one you need.
Calculator
Formula
Description
Spurious-free dynamic range is the ratio of the wanted signal to the largest unwanted spur (harmonic or spurious tone) in the spectrum. It defines the usable dynamic range of a converter or receiver: a small signal can only be detected if it sits above the worst spur. SFDR is critical in communications and instrumentation where weak signals must be found near strong ones.
Variables
- SFDR — Spurious-free dynamic range (dB)
- Vsignal — Amplitude of the fundamental (V)
- Vspur — Amplitude of the worst spurious tone (V)
Practical Notes
SFDR is often specified separately from SNR because a single spur, not the broadband noise, limits the ability to resolve small signals. Dithering can trade SFDR against noise floor.
Symbols and units
| Symbol | Meaning | Default unit | Accepted units |
|---|---|---|---|
| SFDR | SFDR | dB | dB |
| Vsignal | Signal Amplitude | V | pV, nV, µV, mV, V, kV |
| Vspur | Worst Spur Amplitude | mV | pV, nV, µV, mV, V, kV |
Step by step
- 1. What you know: Signal Amplitude 12 V, Worst Spur Amplitude 0.6 V
- 2. The relation: SFDR = 20 × log10(Vsignal / Vspur)
- 3. Substitute: Vsignal = 12 V, Vspur = 0.6 V
- 4. Result: SFDR = 26.02 dB
Worked examples
Minimum range
Given: Signal Amplitude 0.33 V, Worst Spur Amplitude 10 mV
Result: SFDR = 30.37 dB
Low range
Given: Signal Amplitude 3.3 V, Worst Spur Amplitude 100 mV
Result: SFDR = 30.37 dB
Typical
Given: Signal Amplitude 12 V, Worst Spur Amplitude 0.6 V
Result: SFDR = 26.02 dB
High range
Given: Signal Amplitude 0.23 kV, Worst Spur Amplitude 0.9 V
Result: SFDR = 48.15 dB
Maximum range
Given: Signal Amplitude 2.3 kV, Worst Spur Amplitude 9 V
Result: SFDR = 48.15 dB
Solving for each variable
Solve for SFDR
Signal Amplitude 0.33 V, Worst Spur Amplitude 10 mV → 30.37 dB
Solve for Signal Amplitude
SFDR 0.3 dB, Worst Spur Amplitude 10 mV → 10.35 mV
Solve for Worst Spur Amplitude
SFDR 0.3 dB, Signal Amplitude 0.33 V → 0.3188 V
How SFDR changes with Signal Amplitude
| Signal Amplitude (input) | SFDR (result) |
|---|---|
| 1.2 V | 6.021 dB |
| 3 V | 13.98 dB |
| 6 V | 20 dB |
| 9 V | 23.52 dB |
| 12 V | 26.02 dB |
| 18 V | 29.54 dB |
| 24 V | 32.04 dB |
| 48 V | 38.06 dB |
| 84 V | 42.92 dB |
| 120 V | 46.02 dB |
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<p><a href="https://vbatpower.com/formulas/sfdr/">Spurious-Free Dynamic Range</a> Calculator by vbatpower.com</p>Frequently asked questions
How do you calculate Spurious-Free Dynamic Range?
Use SFDR = 20 × log10(Vsignal / Vspur). With Signal Amplitude 12 V, Worst Spur Amplitude 0.6 V, SFDR works out to 26.02 dB.
What is the formula for Spurious-Free Dynamic Range?
The formula is SFDR = 20 × log10(Vsignal / Vspur). Spurious-free dynamic range is the ratio of the wanted signal to the largest unwanted spur (harmonic or spurious tone) in the spectrum.
How do you find Signal Amplitude when you know the other values?
Rearrange for Signal Amplitude: with SFDR 0.3 dB, Worst Spur Amplitude 10 mV, Signal Amplitude is 10.35 mV.
How do you find Worst Spur Amplitude when you know the other values?
Rearrange for Worst Spur Amplitude: with SFDR 0.3 dB, Signal Amplitude 0.33 V, Worst Spur Amplitude is 0.3188 V.
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