Вот тут
http://industrial.panasonic.com/www-data/p.../AOA0000PE8.pdf в 9 разделе приводят странную формулу
Цитата
Noise Index (dB) = A – 10 Log (w l t)
A: Resistive material, value by manufacturing condition
w • l • t: W-dimensions, L-dimensions, t-dimensions
Причем тут размеры, вообще непонятно.
С другой стороны нашел такую щитату
Цитата
Current noise is the bunching and releasing of electrons associated with current flow. The amount of current noise (or lack thereof) depends largely on the resistor technology employed, and it is measurable and is expressed as a function of the input voltage. The magnitude is microvolts per volt applied. A noise index is expressed in decibels, and the equation converting μV/V to dB is:
dB = 20 x log (noise voltage [in μV]/DC voltage [in V]).
For example, 0 dB equates to 1.0 μV/V, and 15 dB equates to 5.6 μV/V.
Что делает оперделение еще запутаннее