| Deutsche Version |
| Formula for the rms noise voltage: |
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| Boltzmann constant | kB = 1.3806505×10-23 J/K (joule/kelvin); J = W · s |
| Absolute temperature in kelvin | T = 273.15 + |
| Bandwidth being considered | Δ f = f2 − f1 = fmax − fmin in Hz; 20 kHz − 20 Hz = 19980 Hz |
| Resistance of the circuit element |
R. R does not mean the universal gas constant! |
To each noise potential the temperature and the bandwidth must be indicated,
with which it was measured.
Don't forget the minus sign, when you enter the noise voltage level.
| Thermal noise: Also called Johnson noise, is the random white noise generated by thermal agitation of electrons in a conductor or electronic device. It is produced by the thermal agitation of the charges in an electric conductor and is proportional to the absolute temperature of the conductor. It manifests itself in the input circuits of audio equipment such as microphone pre amps, where the signal levels are low. The thermal noise level is the limiting minimum noise any circuit can attain at a given temperature. Modern high-quality microphone pre amps, under proper conditions, have noise specifications that come very close to this theoretical limit.
Noise figure NF or noise factor F: Noise figure NF = 10 log (noise factor F) in dB Noise temperature Te = T0 (F − 1) It is determined by EIN means Equivalent Input Noise. It is a specification that helps measure the "quietness" of a gain stage by deriving the equivalent input noise voltage necessary to obtain a given pre amps output noise. Numerically, it’s the output noise at a given gain setting minus the gain. EIN is usually measured at maximum gain and typically ranges from −125 to −130 dBu. Signal-to-noise ratio, often abbreviated SNR or S/N, is an electrical engineering concept defined as the ratio of a signal power to the noise power corrupting the signal. In less technical terms, signal-to-noise ratio compares the level of a desired signal (such as music) to the level of background noise. The higher the ratio, the less obtrusive the background noise is. |
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