Resistor Noise Calculator (Johnson-Nyquist Thermal Noise)

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The resistance value of the resistor or equivalent source impedance. Higher resistance produces more thermal noise.
Operating temperature of the resistor. Room temperature is 25 C (298.15 K). Reducing temperature is one of the few ways to reduce Johnson noise.
The noise bandwidth of the circuit or measurement. Total integrated RMS noise scales with the square root of bandwidth.
RMS Noise Voltage
0.4058uV

Integrated RMS thermal noise voltage across the bandwidth

Noise Spectral Density12.832nV/rtHz
Available Noise Power-143.85dBm
Noise Level-127.83dBV
Temperature298.15K
-127.83 dBV
Sub-noise floor<-160Excellent (low)-160--130Good-130--110Moderate-110--80High noise-80+

0.4058 uV RMS noise: very low thermal noise (sub-1 uV), well-suited for sensitive circuits.

  • The noise spectral density is 12.8 nV/rtHz. This value is independent of bandwidth, making it the most useful figure for comparing noise sources.
  • Doubling the resistance increases noise voltage by a factor of sqrt(2), approximately 1.41. Quadrupling resistance doubles the noise voltage.
  • Cooling the resistor from 25 C to -196 C (liquid nitrogen, 77 K) would reduce noise voltage by a factor of sqrt(298/77), approximately 1.97, nearly halving it.
  • The available noise power (-143.9 dBm) depends only on temperature and bandwidth, not resistance. This is the thermal noise floor for any matched receiver.

Next stepTo minimize noise in your design, reduce source impedance where possible, operate at the lowest feasible temperature, and limit bandwidth to only what the signal requires.

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