John Larkin wrote:> On Mon, 23 Jul 2012 01:16:24 -0700, Robert Baer > <robertbaer@localnet.com> wrote: > >> 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. >> > > > > Some of my scribbles on the subject: > > https://dl.dropbox.com/u/53724080/Circuits/Zener_Noise.pdf > >Check! That is what i saw (no pun intended).
Zener noise / oscillations
Started by ●July 23, 2012
Reply by ●July 24, 20122012-07-24
Reply by ●July 24, 20122012-07-24
Bill Sloman wrote:> On 7/23/2012 10:16 AM, Robert Baer wrote: >> 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 $$. > > There was a nice - and tolerably long - thread on the subject "Zener > Diode Oscillation" - here back in 1997. Winfield Hill and the late > Tony Williams posted a lot of interesting measurements and some > interesting references from the semiconductor physics literature. >I remember a while back references to that; sounded worthy of a textbook. Is that thread or (one) book available,and where?
Reply by ●July 24, 20122012-07-24
Jan Panteltje <pNaonStpealmtje@yahoo.com> writes:> On a sunny day (Mon, 23 Jul 2012 18:12:40 +0100) it happened John Devereux > <john@devereux.me.uk> wrote in <87k3xu2ygn.fsf@devereux.me.uk>: > >>Jan Panteltje <pNaonStpealmtje@yahoo.com> writes: >> >>> On a sunny day (Mon, 23 Jul 2012 14:53:16 +0100) it happened John Devereux >>> <john@devereux.me.uk> wrote in <87sjci37oz.fsf@devereux.me.uk>: >>> >>>>Jan Panteltje <pNaonStpealmtje@yahoo.com> writes: >>>> >>>>> On a sunny day (Mon, 23 Jul 2012 01:16:24 -0700) it happened Robert Baer >>>>> <robertbaer@localnet.com> wrote in >>>>> <BeCdnSnrv6HGlZDNnZ2dnUVZ_qudnZ2d@posted.localnet>: >>>>> >>>>>> 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 $$. >>>>> >>>>> I do not normally use zeners for reference, just for over voltage protection. >>>>> For reference you probably want bandgap based chips. >>>>> There are some very low power reference chips. >>>> >>>>Bandgap ones are more convenient. But the very best semiconductor >>>>references in terms of noise and stability are those based on zeners. >>> >>> At 2-50uA? >> >>Not as far as I know - usually about 5mA and ~6-7V. Like I said, not >>very convenient. > > Yes, I remember those (Intermetal IIRC) had a zener and Ge transistor > that used together (zener in emitter) had exactly a zero Tc. > Indeed about 5 or 6V, do not remember the exact value. > For the rest the Tc is never really flat for zeners AFAIK...There are "TC Zeners" that are still, just about, available. 1N82x for example. <http://uk.farnell.com/jsp/search/results.jsp?N=731&Ntk=gensearch&Ntt=1n82&Ntx=mode+matchallpartial> These are zeners with forward biased (silicon) diodes in series with them. The TCs cancel, very well for some parts. 1N829 is guaranteed < 5ppm/K over a huge temperature range. These end up being 6.2V usually, there are also combinations with two forward biased diodes and other zener voltages so you could other voltages like 11V. There were also "reference amplifiers" that used a transistor b-e junction instead of the forward biased diode, and pinned out the collector so it could be used as part of the regulation circuit. Never heard of the Ge transistor ones, I guess that gives you another combination. But I was actually thinking of the integrated types, LT1236, LM199, LTZ1000 for example. -- John Devereux
Reply by ●July 24, 20122012-07-24
bloggs.fredbloggs.fred@gmail.com wrote:> On Monday, July 23, 2012 4:16:24 AM UTC-4, Robert Baer wrote: >> 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? >> * > > > That is not noise, you have inadvertently built a negative resistance oscillator: > http://www.tandfonline.com/doi/abs/10.1080/00207219408926109#preview"sorry you do not have access to the article"
Reply by ●July 24, 20122012-07-24
George Herold wrote:> On Jul 23, 4:16 am, Robert Baer<robertb...@localnet.com> wrote: >> 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 $$. > > What sort of voltage range are you talking about. My limited > experience would suggest that at lower voltage (8-16 V) the low > current noise is very variable piece to piece. > > At higher voltage the low current noise is larger and more consistent > > And above 20 (something) Volts there maybe a point in the I-V curve > that can lead to oscillations. > > Though all of this depends on the power rating of the diode too. > > George H.I do not care about the voltage rating of the zener. So far,i have tested some of the BZX84Cxx series (Vishay, as the co$t is low), and the 18V and 22V look "good" ; the Fairchild 18V was rather ugly. Also tested a number of the MMBZ52xxB series (Vishay, as the co$t is low),16V to 27V; some were not too bad and a few were terrible. Recently got the 68V and 75V zener, and WOW! The 68V zener was the most ugly negative resistance oscillator and noise zener i had ever seen! Fully recommend it if that is what you need. OTH the 75V looks perfect - meaning i better find a decent way to check its dynamic resistance VS current - - getting back to (one of my questions) how to do that in a reasonable manner, without unduly "upsetting" the zener. Need minimal Heisenberg here..
Reply by ●July 24, 20122012-07-24
George Herold wrote:> On Jul 23, 1:44 pm, bloggs.fredbloggs.f...@gmail.com wrote: >> On Monday, July 23, 2012 4:16:24 AM UTC-4, Robert Baer wrote: >>> 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? >>> * >> >> That is not noise, you have inadvertently built a negative resistance oscillator:http://www.tandfonline.com/doi/abs/10.1080/00207219408926109#preview > > Woah, a 4kV zener! You don't use those every day. > (at least I don't) > > George H.Best i have done is near 2KV for downhole work but can go to 3750V.
Reply by ●July 24, 20122012-07-24
bloggs.fredbloggs.fred@gmail.com wrote:> On Monday, July 23, 2012 2:17:12 PM UTC-4, George Herold wrote: >> On Jul 23, 1:44 pm, bloggs.fredbloggs.f...@gmail.com wrote: >> > On Monday, July 23, 2012 4:16:24 AM UTC-4, Robert Baer wrote: >> >> 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&quot;frequency&quot; as that gives >> >> wrong impression). >> >> Then this&quot;converts&quot; to random noise. >> >> Eventually, there are&quot;bursts&quot; of NO noise. Then at higher current, >> >> noise bursts decrease in&quot;frequency&quot; 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? >> >> * >> > >> > That is not noise, you have inadvertently built a negative resistance oscillator:http://www.tandfonline.com/doi/abs/10.1080/00207219408926109#preview >> >> Woah, a 4kV zener! You don't use those every day. >> (at least I don't) >> >> George H. > > You might note they extended the observations to the low voltage diodes too.Check; that is why i would like to see the whole article.
Reply by ●July 24, 20122012-07-24
Jim Thompson wrote:> On Mon, 23 Jul 2012 18:12:40 +0100, John Devereux > <john@devereux.me.uk> wrote: > >> Jan Panteltje<pNaonStpealmtje@yahoo.com> writes: >> >>> On a sunny day (Mon, 23 Jul 2012 14:53:16 +0100) it happened John Devereux >>> <john@devereux.me.uk> wrote in<87sjci37oz.fsf@devereux.me.uk>: >>> >>>> Jan Panteltje<pNaonStpealmtje@yahoo.com> writes: >>>> >>>>> On a sunny day (Mon, 23 Jul 2012 01:16:24 -0700) it happened Robert Baer >>>>> <robertbaer@localnet.com> wrote in >>>>> <BeCdnSnrv6HGlZDNnZ2dnUVZ_qudnZ2d@posted.localnet>: >>>>> >>>>>> 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 $$. >>>>> >>>>> I do not normally use zeners for reference, just for over voltage protection. >>>>> For reference you probably want bandgap based chips. >>>>> There are some very low power reference chips. >>>> >>>> Bandgap ones are more convenient. But the very best semiconductor >>>> references in terms of noise and stability are those based on zeners. >>> >>> At 2-50uA? >> >> Not as far as I know - usually about 5mA and ~6-7V. Like I said, not >> very convenient. > > I've done bandgaps on CMOS processes... 100uA total operating current. > My bag of tricks includes producing other voltages than the standard > 1.25V/2.5V... handy when you have a low voltage supply... I have one > architecture that goes stable and flat output of +1V, when VCC=1.2V > > ...Jim ThompsonNow THAT must be very handy!
Reply by ●July 24, 20122012-07-24
George Herold wrote:> On Jul 23, 2:37 pm, bloggs.fredbloggs.f...@gmail.com wrote: >> On Monday, July 23, 2012 2:17:12 PM UTC-4, George Herold wrote: >>> On Jul 23, 1:44 pm, bloggs.fredbloggs.f...@gmail.com wrote: >>> > On Monday, July 23, 2012 4:16:24 AM UTC-4, Robert Baer wrote: >>> >> 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&quot;frequency&quot; as that gives >>> >> wrong impression). >>> >> Then this&quot;converts&quot; to random noise. >>> >> Eventually, there are&quot;bursts&quot; of NO noise. Then at higher current, >>> >> noise bursts decrease in&quot;frequency&quot; 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? >>> >> * >>> > >>> > That is not noise, you have inadvertently built a negative resistance oscillator:http://www.tandfonline.com/doi/abs/10.1080/00207219408926109#preview >> >>> Woah, a 4kV zener! You don't use those every day. >>> (at least I don't) >> >>> George H. >> >> You might note they extended the observations to the low voltage diodes too. > > Oh,I don't have access to the whole paper. > I was looking at some data sheets (a while back) and zeners in the > 25V-30V range looked like they might oscillate at the right current. > > (I guess the last thing the OP wants is an oscillator.) > > George H.Check; see my previous posting WRT 68V and 75V zeners.
Reply by ●July 24, 20122012-07-24
bitterlemon40@yahoo.ie wrote:> You can heat treat zener diodes (by passing a lot of current through them) for use in saw-tooth oscillator circuits. Obviously if you that you are causing poorly controlled physical changes of the semiconductor properties. You know a TL431 shunt regulator costs so little these days that you should use it in your circuits in preference to a zener diode. It is so much better and 1960's style voltage regulation is not such a great idea these days.Yes, a TL431 is cheap but the minimal standing current is way above what is needed.
