I want to know more about low-noise zeners. Are they really low noise?
I would like to use instead of LM329, which is more expensive and harder to get.
Any specific type for those low noise zeners? I am looking for 7.5v types.
I would like to use instead of LM329, which is more expensive and harder to get.
Any specific type for those low noise zeners? I am looking for 7.5v types.
This is a good reference.
http://bitsavers.trailing-edge.com/...Books/1991_Motorola_TVS_Zener_Device_Data.pdf
http://bitsavers.trailing-edge.com/...Books/1991_Motorola_TVS_Zener_Device_Data.pdf
zeners are often used in white noise generators. 1N755A=7.5v, IN759A=12v. Higher voltage zener has more noise. Resistors and caps have noise. Best not to worry too much .. just capture it with capacitors.
https://www.sciencedirect.com/topics/engineering/thermal-noise
Gerhard Hoffman who really knows his beans, has commented often on the BCxxxxx zeners as very low noise (and easily available).
I had several packs 100 LM329DZ from DK which supplied many a Jung-Didden super-regulator, only about a dozen left.
At any rate, and in absolute truth, when we did the "great regulator bake-off" for LinearAudio noise was the least important factor in the critical analysis.
I posted in the "parts" segment some analysis of Analog Devices new ultra voltage reference, the ADR1000
I had several packs 100 LM329DZ from DK which supplied many a Jung-Didden super-regulator, only about a dozen left.
At any rate, and in absolute truth, when we did the "great regulator bake-off" for LinearAudio noise was the least important factor in the critical analysis.
I posted in the "parts" segment some analysis of Analog Devices new ultra voltage reference, the ADR1000
I had a quick look on Mouser for those, they didn't show in a quick search. Gerhard's posts are really illuminating, he recommends NXP 2V7 true zeners for low noise (around 2nV/rtHz according to him). The disadvantage of them is their relatively high dynamic resistance (typ 75R for BZX84C2V7) whereas the noisier, higher voltage zeners* get down to ~6R.
*Higher voltage zeners are really avalanche mode, not truly zeners.
The problem is that where I live, Brazil, is too expensive to import parts from the USA. So I will use 7.5v zeners instead of LM329 for my Superregulator.
I just tried it for a BZX84C6V2L and seems not. But each part has its own parameters so its possible others include noise.
Somewhere around 5 to 6 V, the temperature coefficient becomes zero because the Zener and avalache effects both play a role and their temperature dependencies have opposite signs. If you want only Zener effect, you have to use Zener diodes well below 5 V.
Member @gerhard provided some professional noise measurements that include several zener diodes:
https://www.diyaudio.com/community/...-for-leds-and-zener-diodes.35821/post-5548587
In example, BZX84C2V7 and BZX84C3V3 have outstanding low noise at about 2 nV/rtHz, while BZX84C6V8 has about 16 nV/rtHz.
https://www.diyaudio.com/community/...-for-leds-and-zener-diodes.35821/post-5548587
In example, BZX84C2V7 and BZX84C3V3 have outstanding low noise at about 2 nV/rtHz, while BZX84C6V8 has about 16 nV/rtHz.
Probably a typo. BC*** are small signal low frequency transistors.
In the European system:
1st letter A=Germanium B=Silicon C=GaAs, really defined by bandgap range
2nd letter A=diode B=Varicap C=small signal transistor D=power trans
F=small sig RF L=power RF Y=fat diode Z=Zener
3rd letter, if present and usually from end of alphabet: professional use, pinout options
digits: to tell them apart
< https://www.digikey.de/de/products/...en/287?s=N4IgTCBcDaIEIC0AaAOALAYTANQOwgF0BfIA >
HLMP-6000, from HP. Avago, now Broadcom is probably king of the hill.
Optically quite a dimmbulb. I have the belly feeling: the brighter, the more noise.
< https://www.digikey.de/de/products/detail/broadcom-limited/HLMP-6000/637657 >
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Just saw, you want 7.5V. That would be a diode based on avalanche effect.
Hopeless.
3 * 2.5V in series would present much less noise. First, they produce
less noise and then the DC-voltage adds in a linear way, and the noise
with the square root.
Hopeless.
3 * 2.5V in series would present much less noise. First, they produce
less noise and then the DC-voltage adds in a linear way, and the noise
with the square root.