Noise voltage

The noise voltage U _R is the thermal resistance noise (so-called white noise ) at a certain measured frequency - bandwidth B or . ${\displaystyle \Delta f}$

The noise voltage is not a specific value, but is determined by a specified measurement bandwidth; Noise values ​​without the associated bandwidth say nothing. Example: is the noise of a resistor in a 1 Hz wide frequency range, e.g. B. from 1 Hz to 2 Hz, measured, the same measured value results as with a measurement of z. B. 19,999 Hz to 20,000 Hz. In other words, the power spectral density of the white noise is constant.

At a constant temperature  T and a fixed resistance value  R , the noise voltage that can be measured at the resistor changes proportionally to the square root of the measurement bandwidth : ${\displaystyle B=\Delta f}$

${\displaystyle U_{\mathrm {R} }={\sqrt {4k_{\mathrm {B} }\cdot T\cdot R\cdot B}}.}$

Where:

• the Boltzmann constant k _B = 1.3806505 · 10 ⁻²³ J / K ( Joule / Kelvin); J = W s
• the absolute temperature T in Kelvin = 273.15 + in ° C ${\displaystyle \vartheta }$
• the resistance R in ohms
• the considered bandwidth B = f ₂ - f ₁ in Hz

literature

• Gregor Häberle, Heinz Häberle, Thomas Kleiber: Expertise in radio, television and radio electronics. 3rd, revised and expanded edition. Verlag Europa-Lehrmittel, Haan-Gruiten 1996, ISBN 3-8085-3263-7 .
• Thomas Görne: Sound engineering. Fachbuchverlag Leipzig in Carl Hanser Verlag, Munich et al. 2006, ISBN 3-446-40198-9 .
• Martin Werner: Communication technology . Analog and digital processes with modern applications, Friedrich Vieweg & Sohn Verlag, Wiesbaden 2006, ISBN 3-528-04126-9 .
• Herbert Bernstein: LF and HF measurement technology. Measuring with oscilloscopes, network analyzers and spectrum analyzers, Springer Fachmedien, Wiesbaden 2015, ISBN 978-3-658-07377-0 .

Web links

• Calculation of the effective noise voltage
• Noise (accessed October 13, 2017)
• The noise (accessed October 13, 2017)
• Noise Noise types (accessed October 13, 2017)