Zener-noise (current)

In absolute terms, the current noise in the zener rises as you increase the current. The rate of rise is less than linear so the portion of the current that is noise decreases.

The voltage noise on a zener ideally decreases with current. If there is a resistance in series, the combined effect can be an increase in noise voltage with increasing current.

Does this help?

What was the Zener voltage. I looked at the current noise from an

George H.

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There's also the distinction between Zener didoes that work by the Zener mechanism - breakdown voltages below about 6.2V - and the hgiher voltage Zener diodes that work by an avalanche mechaism, which is noisier.

It's all fun stuff, and Spice doesn't model any of it.

The 1997 thread on "ZENER DIODE OSCILLATION" has lots of good information on the subject.

-- Bill Sloman, Nijmegen

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Thanks for the 'hint' Bill. I've found some of the old papers from the 50's and will read them over. Sounds like you all had some fun back in the summer of '97.

George H.

One cannot use any version of Spice to even guesstimate noise of any zener diode at any given current - from nanoamps to tens of milliamps. Firstly, a given 1N zener will have different noise characteristics at a specified current from vendor to vendor. Secondly, noise and usually concurrent negative resistance will vary all over the map for a given diode as current is varied from near zero to (say) 20mA. Usually, noise and negative resistance starts very close to zero current and usually dies out in the 5-20mA region (and does not return even up to burnout). And there are a number of exceptions to put the lie to the word "usually" above. Some seem to have no visible negative resistance over some (nondescript) current range, either abruptly starting as current is increased, or abruptly stopping as current increased (the other "end" being "graceful"), and others are "graceful" startup / stopping. Variables: manufacturer, zener voltage rating, current drive. change any one and you are not only in a different ballpark but could be in a different city or even planet!

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This is Great! Just finished K.G. McKay "Avalanche Breakdown in Silicon", Phys. Rev ('54) 94, 877. The discussion of Breakdown Instabilty at the end of the paper is exactly what I observe. (Nice to know I can see what was done before I was born at Bell labs.) John L. I know you've measured zener voltage noise, but have you looked at the current noise?

McKay also talks about a temperature dependence which sounds like more potential fun!

I'd really like avalanche zeners to behave like PMT's and give shot noise that is much larger than that for single electron events, but still finite. I guess I have to run them below the 'knee' but at a point where there is still some multiplication, just not infinite. (Hmm, thermal stability might be an issue???)

George H.

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Hi all,

Thanks for the reaction!! I did some extra test on temperature and I see similarities with what you all are saying.

But now I only measure the RMS Voltage so I get an idea about the Thermal Noise.

How can I get some information about the Shot Noise, is there also a simple way to measure this??

Thanks in advance.

Bosken

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Hi Bosken, You still haven't told us the voltage of the Zener, nor what current you are running it at. Just because you are measuring voltage I wouldn't call it thermal noise. A few months ago I would have been tempted to call it shot noise, but I would have been wrong. Let's just call it zener noise. You can measure the zener voltage noise as you have been doing. To measure the current noise from a zener you can put a resistor in series with the zener and measure the voltage across it. You need to keep the value of the resistor below the impedance of the zener at the operating point... determined from the I-V slope at that point. You can also run the zener into an opamp configured as a current to voltage converter... 'course then your bandwidth will be limited by the opamp. Depending on how you are biasing the zener you may also need to 'short out' the bias resistor with a capacitor. (You need to supply a low impedance path for the AC noise current.)

Have fun,

George H.

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Hi George.

The zener that I use is a 6.2 voltage zenerdiode, the current will be around

Do you say that the contribution of Shotnoise also can be measured by measuring the Noise Voltage? It seems strange to me because Shotnoise comes from the current thought the potential barrier. Or is my approach to literally? I just want to get an idea of what I am measuring...

I will test the current measurement with a resistor, thanks for the tips!

Bosken

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