Le bruit dans les jonctions.
Certains forumers anglais ont pris le multimètre sophistiqué à 2 mains et ont éssayé de mesurer le bruit de différentes jonctions.
Les résultats sont intéressants, même s'ils ne disposaient que de peu d'échantillons.
- noise_test_rig1a.png (65.08 Kio) Vu 2677 fois
"I'll try to briefly summarize the conclusions one might perhaps try to draw from the results:
The least noisy choice is an IR LED running at close to maximum current.
Blue LEDS share the property with IR LEDs that they get less noisy with larger current, but they are so noisy compared to
other LEDs that they are best avoided.
All other LEDs seem to have an optimal current for low noise.
however, don't draw the conclusion that this optimum is at 5mA just because I happened to use that as one of the test currents.
Further investigation is needed to find the optimum current for various LEDs. The differences between colour in
the red to green area or for differenc currents are small though and nothing to loose sleep over. Red LEDs at optimum current
seem the least noisy, though (next to IR LEDs at high current, that is).
Zener diodes seem an altoghether different and more confusing story.
Below approximately 6V they have true zener breakdown and above this they have avalanche breakdown.
It was thus obvious to test zeners close to and to each side of this "transition region" and also zeneres far into each region.
Surprisingly, the important distinction seems not to be which type of breakdown they exhibit, but how close to or far away
from the transition they are.
Low volt and high volt zeners turned out to have moderate noise and the high voltage avalanche type could even rival most LEDs.
Those diodes close to the transition, on the other hand, turned out to be noisy as h**l (maybe the electrons are confused and
don't know if they are doing a zener breakdown or an avalanche one? ).
Zener diodes generally share with IR and blue LEDs that the get less noisy with larger currents.
For high power zeners vs. low power zeners, the high power ones seem more noise in the zener region and less noisy in
the avalanche region.
Since these diodes could take higher currents, the noise could probably be brought down by
and rival the LEDs if going far above 20mA.
( From DIY: http://www.diyaudio.com/forums/parts/35 ... iodes.html)
Un bloggeur a également fait des mesures:
- http://www.ciphersbyritter.com/RADELECT ... ISMEA1.HTM
Il propose d'autres pages également sur le bruit.
Enfin, comme quoi une zener soi-disant bruyante, ajouté à un collecteur commun, devient une des références de tension la moins bruyante:
- http://www.tnt-audio.com/clinica/regula ... se3_e.html
(En fin de page)
L'article complet est également intéressant sur le bruit de différents composants utilisés en audio, et ailleurs.
Les jonctions sont bruyantes, mais pas tant que ça, et en faisant du trie, on arrive à trouver son bonheur.
Une carte son de bonne qualité, ainsi qu'un logiciel FFT permettraient de faire un tri satisfaisant.
Les bricoleurs de DIY utilisent souvent des LED pour stabiliser leurs tensions et courants.
La diode zener utilisée dans le tuner Braun CE500 doit générer moins de 1µV de bruit.
On doit pouvoir s'en satisfaire.
