Zener noise / oscillations

Robert Baer · 2012-07-23T08:16:24+00:00

Zeners all seem to behave: quiet, no oscillation IF run at or near the spec current (usually in the tens of mA). But, if one needs to run them at low currents (say 10uA to 500uA) then _watch_out_! Some brands at certain voltages are extremely noisy and subject to oscillation. The waveforms seen at low currents (2-50uA) look like randumb sawtooth generation, and as the current is increased the amplitude and probability increases (do NOT want to say "frequency" as that gives wrong impression). Then this "converts" to random noise. Eventually, there are "bursts" of NO noise. Then at higher current, noise bursts decrease in "frequency" and amplitude. That is what i see in general. However, i have found two zeners that, on a curve tracer, one sees little if any noise or spikes mentioned. NOW for the question: How can one test these particular zeners to ensure they do not or will not oscillate?* Yes, there are zeners made for low noise and those have a much lower spec current, BUT i cannot afford to have the factory dig the silicon mines, etc much less the high $$.

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Tim Williams 13 years ago

Why not? I've seen 2500, even 4000V parts (like Speff's link). Not very useful (a good old EL509 has better switching, conduction and voltage performance, if lower gain), but they're out there.

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They'll have a better price in quantity, though they don't show it on this view. Digikey pricing is inflated by 2-3 times.

There ought to be a 1A 1500V part out there that's even cheaper. Note that TO-220 is dubious at this voltage, but a bulkier TO-247 package will cost more. DPAK2 or DPAK3 would actually be pretty handy, since lead spacing is moderate, size is compact, and heat dissipation is via PCB. If you're encapsulating it anyway, it'll be no problem.

A stack of 20 (about $80 at this price) will get you 30kV standoff, which should be enough.

Note bipolar transistors aren't useful here; HOTs typically break down at only 800V (Vceo), with high leakage and secondary breakdown. MOSFETs are best at high voltage linear applications.

Tim

Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms "Robert Baer" wrote in message news:SZKdnXwyDtUP_orNnZ2dnUVZ_rGdnZ2d@posted.localnet... > Tim Williams wrote: >> "Robert Baer" wrote in message >> news:XeGdnYP1n4WMe4nNnZ2dnUVZ_jSdnZ2d@posted.localnet... >>> Well, ASS-u-ME-ing an additional supply, one could use a 431, a FET >>> and a few resistors (variant on our original Codatron(TM) design) to >>> produce a decent 500V reference, and then stack a bunch of FETs and >>> resistors to multiply by 50..too expensive. >> >> So a $2 transistor and two resistors for each subsequent 1500V is too >> much? And a stack of 431s (if they worked) isn't??? >> >> Then your product is impossible. >> >> Tim >> > There is NO transistor that can take 1500V reliably; and at $2 each? > FURRgeddit sez the FURRy Baer. >

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JW 13 years ago

output.

A bit more conventional:

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Michael A. Terrell 13 years ago

Apparently:

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Fred Abse 13 years ago

IME, datasheet specs are often way off reality.

"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)

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Fred Abse 13 years ago

P31 is *green*. Medium persistence. AKA "DG" in Europe.

"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)

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Fred Abse 13 years ago

Ouch!

You wanna ruin my day?

Prep H doesn't work for me ;-(

"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)

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Fred Bartoli 13 years ago

Then try a bridge (super ouchhhh....)

Thanks, Fred.

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Fred Abse 13 years ago

Dentures in my a$$?

"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)

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John S 13 years ago

Well, then don't put it there. Put it where it hurts.

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Fred Abse 13 years ago

Looking at your bipolar transistor breakdown pics, assuming that they've not been massaged, I see a *green* (P31) phosphor with a yellow-tinted neutral-density filter. The trace still looks green, as one would expect thru a yellow filter.

My color vision is normal, btw.

"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)

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Jasen Betts 13 years ago

You can get tinted neutral density filters?

?? 100% natural --- Posted via news://freenews.netfront.net/ - Complaints to news@netfront.net

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Fred Abse 13 years ago

Green Ray-Bans, for a start...

-- "For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)

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krw 13 years ago

If they're green they're not "neutral".

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Fred Abse 13 years ago

Strictly no, but they aren't green either. Similar to a 3.0 ND filter plus a 0.25G filter. Largely neutral, with a green bias.

"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)

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krw 13 years ago

Would you use such a filter for color photography? ;-)

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Fred Abse 13 years ago

I've used fairly odd filter packs for negative color printing. The difference is that the filters were complementary colors, say 0.5C plus

0.5Y, producing a magenta (minus green) correction in the end result (subtractive process). The more expensive enlargers, like Macbeth, had dial-in filters. All I had was a drawer you put a stack of actual gelatin filters in. Then you had to recalculate the exposure.

I'm glad that digital got rid of the tiresome chemistry part of photography, playing with test strips, and so on.

"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)

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krw 13 years ago

Post processing, sure. You don't throw away information in the camera or on the film, though.

I thought B&W photography and wet room work was a lot of fun. I did a lot (10-15 rolls a week) in college. I did very little color, though. It never held any attraction.

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Fred Abse 13 years ago

I always preferred B&W. The world's best pictures, Robert Capa, Ansel Adams, the Paris Match photojournalists, etc, were almost exclusively B&W.

"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)

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Jan Panteltje 13 years ago

On a sunny day (Wed, 08 Aug 2012 10:09:55 -0700) it happened Fred Abse wrote in :

I did a lot in BW, had an enlarger (Durst), developed the films and the prints.

I am so glad all is digital now!

I remember pulling film out under a blanket, and putting it in a small container, and then shaking it..

Miracle it all worked. Apart from 35 mm there also was 6x6cm films.

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Spehro Pefhany 13 years ago

I had a Durst M301 WAYYYY back.

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Zener noise / oscillations

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