zener diode high performance

[Stefanoo]

Hi everybody!

I would like to know where i can get high performace zener.

i'm searching for a very low noise zener diode.

As for example Caddock or vishay manufactr not inductive resistors, i would like to know who makes very high quality zener diode.


Hope to receive advice.


Best Regards,
Stefano.

 

[EchoWars]

Never heard of a high-performance zener.

The standard ones seem to be used pretty much everywhere with little or no complaint...the tricky part likely being in how you filter it.

 

[Stefanoo]

well, as there are high grade resistors, capacitor, bridge rectifier.....and so on..... there are high grade zener.
Those zener have better performances due to a sharper knee and straigther characteristic and lower noise.

The only problem is that i don't know the name of the manufacters that make those components.

Hope somebody can help.


Best,
Stefano.

 

[peranders]

A LM329 is quite OK if you can use 7 volts.

 

[Stefanoo]

the voltages that i need are:

10V ; 6,2V

 

[peranders]

Can you tell me the circuit they will be in? Maybe you don't need anything special

By it's nature zeners are noisy so if you really need a quiet zener like part you may look for other solutions.

 

[hacknet]

would resistor divider help?

 

[Stefanoo]

ok thanks for the advice.

The zeners would go:

as stab on the base of a npn in configuration current sink on the tail of the input differential stage.


The point is that i would like to re-place this part on my amp (electrocompaniet).
As far as i know there is an upgrade available from the company that involves the upgrade of this zeners (and also other parts).

That's why i'm searching zener to go on my amp's board that are higher quality.

as i said i would need a 10V and 6,2V

 

[peranders]

Remember that the noise in this stage is created by the input transistors, not the current source. What you can do is to filter the noise. Check out here. Look at R6, C4 and C6.

 

[Stefanoo]

yes, thanks for the explanation.
But in that point a stable zener would contribuite a more linear stage (because the current mirror would be more ideal).

another zener is placed on the source of an differential stage.

 

[peranders]

More ideal, how? Higher output impedance or what?

 

[EUVL]

Low noise Zener

Someone posted his measurements once for LEDs, and there are also data for Zener, both 0.5W & 1.3W.

I think there is no real argument for using LEDs according to his results.

Here is the link :

http://www.diyaudio.com/forums/showthread.php?postid=417008#post417008


Patrick

 

[Stefanoo]

Ideal in the sense of more constant current source (sink).
The more stable is the zener at the base and less noisy, the more stable will be the current sink and the more linear the differential stage will be.
But i might be wrong.

I just need to know who manufacter higher grade zener diodes.

 

[EUVL]

> Ideal in the sense of more constant current source (sink).

A Zener is a device used to keep the voltage constant under varying load (i.e. it absorbs variations in load current). So unless your load sinks constant current, and you feed it AND the zener with a CCS, the Zener current is not meant to be stable. Or have I missed something ?

> I just need to know who manufacter higher grade zener diodes.

If you have already read the article linked earlier, you will have no doubt notice that the part no. etc of the tested Zeners were mentioned.


Patrick

 

[Stefanoo]

i expressed very bad my self before.... anyways i'm searching for a sharp knee and straight characteristic.
But maybe all the zeners are the same as any other zener... i don't know.... !!!!

 

[peranders]

Sharp knee etc. has to do with voltage AND manufacturing parameters so performance is a relative thing.

 

[jan.didden]

Ideal in the sense of more constant current source (sink).
The more stable is the zener at the base and less noisy, the more stable will be the current sink and the more linear the differential stage will be.
But i might be wrong.

I just need to know who manufacter higher grade zener diodes.

There are no high performance zeners in the sense that there are high performance R's and C's. The noise from a zener comes from the fabrication process and cannot be changed by some magic. Also, dynamic impedance (knee) depends on the zener voltage. The higher the zener voltage, the higher the dynamic impedance. There seems to be a minimum dynamic impedance for 6-7V zeners, anything above or below gets worse.

If you need low noise, get a zener, filter it with an R-C and buffer it with a transistor or fet as emitter/source follower. Or get a voltage reference, they are available for lower noise because they use other processes.

Jan Didden

 

[ilimzn]

jan has, as usual, nicelly summed it all up.
The added problem with selection is that noise is related to zener voltage in a quite different (you culd almost say oposite) manner. 5-8V zeners are unusually good nosie sources.
Also, thermal gradient changes depending on zener voltage.
So, in other words, you have to select based on what parameters are of greater importance for the application.

 

[roender]

5-8V zeners are unusually good nosie sources.
Also, thermal gradient changes depending on zener voltage.

5-8V "zeners" are not zener nor avalanche diodes ...
Thermal drift can be compensated with a 1n4148 series diode.

 

[unclejed613]

zener noise comes from the way a zener operates. the noise comes from the somewhat random random recombination of electrons with carriers within the silicon (the same effect happens in a gas tube regulator when the electrons recombine with the positive ions on the plate of the tube). a higher wattage zener will have a higher juncion capacitance, giving less noise (and the higher wattage rating makes it run cooler, so there is less thermal variation, and less added thermal noise), but a zener is usually also heavily bypassed where noise is an issue.