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...>-- > >John Devereux >
Zener noise / oscillations
Started by ●July 23, 2012
Reply by ●July 23, 20122012-07-23
Reply by ●July 23, 20122012-07-23
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
Reply by ●July 23, 20122012-07-23
On Jul 23, 4:16=A0am, Robert Baer <robertb...@localnet.com> wrote:> =A0 =A0Zeners all seem to behave: quiet, no oscillation IF run at or near > the spec current (usually in the tens of mA). > =A0 =A0But, if one needs to run them at low currents (say 10uA to 500uA) > then _watch_out_! > =A0 =A0Some brands at certain voltages are extremely noisy and subject to > oscillation. > =A0 =A0The 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). > =A0 =A0Then this "converts" to random noise. > =A0 =A0Eventually, there are "bursts" of NO noise. Then at higher current=,> noise bursts decrease in "frequency" and amplitude. > > =A0 =A0That is what i see in general. > =A0 =A0However, i have found two zeners that, on a curve tracer, one sees > little if any noise or spikes mentioned. > =A0 =A0NOW for the question: > =A0 =A0How can one test these particular zeners to ensure they do not or > will not oscillate? > * > =A0 =A0Yes, there are zeners made for low noise and those have a much low=er> 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.
Reply by ●July 23, 20122012-07-23
On Jul 23, 1:44=A0pm, 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). > > =A0 =A0But, if one needs to run them at low currents (say 10uA to 500uA=)> > then _watch_out_! > > =A0 =A0Some brands at certain voltages are extremely noisy and subject =to> > oscillation. > > =A0 =A0The 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). > > =A0 =A0Then this "converts" to random noise. > > =A0 =A0Eventually, there are "bursts" of NO noise. Then at hi=gher current,> > noise bursts decrease in "frequency" and amplitude. > > > =A0 =A0That is what i see in general. > > =A0 =A0However, i have found two zeners that, on a curve tracer, one se=es> > little if any noise or spikes mentioned. > > =A0 =A0NOW for the question: > > =A0 =A0How can one test these particular zeners to ensure they do not o=r> > will not oscillate? > > * > > That is not noise, you have inadvertently built a negative resistance osc=illator:http://www.tandfonline.com/doi/abs/10.1080/00207219408926109#previe= w Woah, a 4kV zener! You don't use those every day. (at least I don't) George H.
Reply by ●July 23, 20122012-07-23
On Monday, July 23, 2012 2:17:12 PM UTC-4, George Herold wrote:> On Jul 23, 1:44=A0pm, 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 n=ear> > > the spec current (usually in the tens of mA). > > > =A0 =A0But, if one needs to run them at low currents (say 10uA =to 500uA)> > > then _watch_out_! > > > =A0 =A0Some brands at certain voltages are extremely noisy and =subject to> > > oscillation. > > > =A0 =A0The waveforms seen at low currents (2-50uA) look like ra=ndumb> > > sawtooth generation, and as the current is increased the amplit=ude and> > > probability increases (do NOT want to say &quot;frequency&a=mp;quot; as that gives> > > wrong impression). > > > =A0 =A0Then this &quot;converts&quot; to random noise. > > > =A0 =A0Eventually, there are &quot;bursts&quot; of NO n=oise. Then at higher current,> > > noise bursts decrease in &quot;frequency&quot; and ampl=itude.> > > > > =A0 =A0That is what i see in general. > > > =A0 =A0However, i have found two zeners that, on a curve tracer=, one sees> > > little if any noise or spikes mentioned. > > > =A0 =A0NOW for the question: > > > =A0 =A0How 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 resistanc=e oscillator:http://www.tandfonline.com/doi/abs/10.1080/00207219408926109#p= review>=20 > Woah, a 4kV zener! You don't use those every day. > (at least I don't) >=20 > George H.You might note they extended the observations to the low voltage diodes too= .
Reply by ●July 23, 20122012-07-23
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 Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Reply by ●July 23, 20122012-07-23
On Jul 23, 2:37=A0pm, 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=A0pm, 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). > > > > =A0 =A0But, if one needs to run them at low currents (say 10u=A to 500uA)> > > > then _watch_out_! > > > > =A0 =A0Some brands at certain voltages are extremely noisy an=d subject to> > > > oscillation. > > > > =A0 =A0The waveforms seen at low currents (2-50uA) look like =randumb> > > > sawtooth generation, and as the current is increased the ampl=itude and> > > > probability increases (do NOT want to say &quot;frequency=&quot; as that gives> > > > wrong impression). > > > > =A0 =A0Then this &quot;converts&quot; to random noise=.> > > > =A0 =A0Eventually, there are &quot;bursts&quot; of NO=noise. Then at higher current,> > > > noise bursts decrease in &quot;frequency&quot; and am=plitude.> > > > > > > =A0 =A0That is what i see in general. > > > > =A0 =A0However, i have found two zeners that, on a curve trac=er, one sees> > > > little if any noise or spikes mentioned. > > > > =A0 =A0NOW for the question: > > > > =A0 =A0How can one test these particular zeners to ensure the=y do not or> > > > will not oscillate? > > > > * > > > > > > That is not noise, you have inadvertently built a negative resista=nce oscillator:http://www.tandfonline.com/doi/abs/10.1080/00207219408926109= #preview> > > Woah, a 4kV zener! =A0You 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 t=oo. 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.
Reply by ●July 23, 20122012-07-23
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 cau= sing poorly controlled physical changes of the semiconductor properties. Yo= u know a TL431 shunt regulator costs so little these days that you should u= se 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.
Reply by ●July 24, 20122012-07-24
Jan Panteltje wrote:> 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. >Reference? Said nothing about that; app is for voltage regulation but zener pass current must be low.
Reply by ●July 24, 20122012-07-24
Jan Panteltje wrote:> 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?My app is only for voltage regulation, not reference purposes; zener current to range from 2-500uA. Gotta be cheeeep 1-3 cents.
