Tim Williams wrote:> "Robert Baer" <robertbaer@localnet.com> wrote in message > news:y4CdnbWbSZcVtpPNnZ2dnUVZ_rGdnZ2d@posted.localnet... >> Yes, a TL431 is cheap but the minimal standing current is way above >> what is needed. > > 1mA? TLV431 is 100uA and 1.240V, much improved. > > Tim >Range needed: 10uA-500uA.
Zener noise / oscillations
Started by ●July 23, 2012
Reply by ●July 25, 20122012-07-25
Reply by ●July 25, 20122012-07-25
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? >> * >> 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 $$. > > For test purposes as far as detecting the negative resistance region, I would think the standard topology of high impedance source charging the parallel combination of zener || C should bring it out. There you would monitor zener current.Worth trying; thanks.
Reply by ●July 25, 20122012-07-25
On a sunny day (Tue, 24 Jul 2012 23:39:15 -0700) it happened Robert Baer <robertbaer@localnet.com> wrote in <WeudnYHn_bcLCZLNnZ2dnUVZ_jOdnZ2d@posted.localnet>:>Tim Williams wrote: >> "Robert Baer" <robertbaer@localnet.com> wrote in message >> news:y4CdnbWbSZcVtpPNnZ2dnUVZ_rGdnZ2d@posted.localnet... >>> Yes, a TL431 is cheap but the minimal standing current is way above >>> what is needed. >> >> 1mA? TLV431 is 100uA and 1.240V, much improved. >> >> Tim >> > Range needed: 10uA-500uA.It is interesting to note that the PIC 18F14K22 is specified with FVR only running at: 1.8V 28 uA 3V 65 uA 5V 101 uA For a reference output of 1.024V I would think that if you put it into sleep mode, that would make your specs... Datasheet page 337 It is possible to send the Vref output to a pin in that mode AFAIK.
Reply by ●July 25, 20122012-07-25
On 7/24/2012 6:31 AM, Robert Baer wrote:> 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?Google groups still has it. Searching on "Zener diode oscillation" in google groups advanced search found it immediately. 96 posts, last post July 20, 1997. https://groups.google.com/forum/?fromgroups#!topic/sci.electronics.design/OZtqC_bPpPU/overview -- Bill Sloman, Nijmegen
Reply by ●July 25, 20122012-07-25
On 24/07/12 09.39, Jan Panteltje wrote: ...> I am using the Microchip MPC1525 refernce, > it outputs 2.5 V while using 100uA, > drop out voltage is typical 137 mV @ 2 mA out.Please note it is spelled: MCP1525 http://www.microchipdirect.com/ProductDetails.aspx?Catalog=BuyMicrochip&Category=MCP1525&mid=11&treeid=2 http://www.digikey.dk/scripts/dksearch/dksus.dll?vendor=0&keywords=MCP1525 http://dk.mouser.com/Search/Refine.aspx?Keyword=MCP1525 Glenn
Reply by ●July 25, 20122012-07-25
On a sunny day (Wed, 25 Jul 2012 16:52:43 +0200) it happened Glenn <glenn2233@gmail.com> wrote in <5010083b$0$285$14726298@news.sunsite.dk>:>On 24/07/12 09.39, Jan Panteltje wrote: >... >> I am using the Microchip MPC1525 refernce, >> it outputs 2.5 V while using 100uA, >> drop out voltage is typical 137 mV @ 2 mA out. > >Please note it is spelled: > >MCP1525Ooops :-)>http://www.microchipdirect.com/ProductDetails.aspx?Catalog=BuyMicrochip&Category=MCP1525&mid=11&treeid=2 >http://www.digikey.dk/scripts/dksearch/dksus.dll?vendor=0&keywords=MCP1525 >http://dk.mouser.com/Search/Refine.aspx?Keyword=MCP1525 > >Glenn > > >
Reply by ●July 25, 20122012-07-25
On Tue, 24 Jul 2012 23:39:15 -0700, the renowned Robert Baer <robertbaer@localnet.com> wrote:>Tim Williams wrote: >> "Robert Baer" <robertbaer@localnet.com> wrote in message >> news:y4CdnbWbSZcVtpPNnZ2dnUVZ_rGdnZ2d@posted.localnet... >>> Yes, a TL431 is cheap but the minimal standing current is way above >>> what is needed. >> >> 1mA? TLV431 is 100uA and 1.240V, much improved. >> >> Tim >> > Range needed: 10uA-500uA.LT1004-1.2 .. about 20 cents. Or if you want to be a cheapskate and live without guarantees, using green LEDs as references has been discussed here a few times. With a one-Vbe drop (eg. follower) the tempco typically isn't nearly as bad as it could be. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
Reply by ●July 25, 20122012-07-25
On Tue, 24 Jul 2012 17:44:08 +1000, Jan Panteltje <pNaonStpealmtje@yahoo.com> wrote:> On a sunny day (Mon, 23 Jul 2012 21:56:19 -0700) it happened Robert Baer > <robertbaer@localnet.com> wrote in > <y4CdnbubSZdrt5PNnZ2dnUVZ_rGdnZ2d@posted.localnet>: > >> 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 Thompson >> Now THAT must be very handy! > > The PIC 18F... has an internal programable bandgap reference, > you can select for 1.024V, and 2 or 3, or 4 x that, > so up to 4.096 V, and uses very low power. > It can probably replace the rest of your circuit too ;-) > >7% accuracy too! -- Using Opera's revolutionary email client: http://www.opera.com/mail/
Reply by ●July 26, 20122012-07-26
Jan Panteltje wrote:> On a sunny day (Tue, 24 Jul 2012 23:39:15 -0700) it happened Robert Baer > <robertbaer@localnet.com> wrote in > <WeudnYHn_bcLCZLNnZ2dnUVZ_jOdnZ2d@posted.localnet>: > >> Tim Williams wrote: >>> "Robert Baer"<robertbaer@localnet.com> wrote in message >>> news:y4CdnbWbSZcVtpPNnZ2dnUVZ_rGdnZ2d@posted.localnet... >>>> Yes, a TL431 is cheap but the minimal standing current is way above >>>> what is needed. >>> >>> 1mA? TLV431 is 100uA and 1.240V, much improved. >>> >>> Tim >>> >> Range needed: 10uA-500uA. > > It is interesting to note that the PIC 18F14K22 is specified with FVR only running at: > 1.8V 28 uA > 3V 65 uA > 5V 101 uA > For a reference output of 1.024V > > I would think that if you put it into sleep mode, that would make your specs... > Datasheet page 337 > It is possible to send the Vref output to a pin in that mode AFAIK.I need a 2-terminal device so tat i can put hundreds of them in series for 25KV. So far, only one person divined that and his comment was trounced, and not politely.
Reply by ●July 26, 20122012-07-26
Bill Sloman wrote:> On 7/24/2012 6:31 AM, Robert Baer wrote: >> 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? > > Google groups still has it. Searching on "Zener diode oscillation" in > google groups advanced search found it immediately. 96 posts, last post > July 20, 1997. > > https://groups.google.com/forum/?fromgroups#!topic/sci.electronics.design/OZtqC_bPpPU/overview > >Thanks! Noticed the (first?) posting by Mike 7/20/97 where he was rather adamant about "No one can produce a sample of a zener that oscillates." and (to me) rather flippantly states "The person who first demonstrated the existence of oscillations in zeners would be up for the Nobel prize." I must state "hogwash", in all that one needs for an oscillator is a device that exhibits negative resistance (note he _does_ mention Dr. Leo Esaki immediately afterwards). eXplicitly to the point, buy some Vishay MMBZ5266C-V-GS08 68V SOT-23 zeners and put them on a curve tracer; very nice negR jump in the 40-60uA region where the voltage DECREASES as the current INCREASES. I think the same die is available in the DO-35 package by Vishay if you need better power dissipation for your oscillator.
