Forums

Zener diode below-threshold reverse current

Started by Tim Wescott June 23, 2016
On Tue, 12 Jul 2016 13:48:32 -0700 (PDT), dagmargoodboat@yahoo.com
wrote:

>On Tuesday, July 12, 2016 at 3:14:43 PM UTC-4, rickman wrote: >> On 7/12/2016 3:08 PM, John Larkin wrote: >> > >> > Mo and I were sitting at a table near the window of our neighborhood >> > French restaurant snacking on beer and oysters and cassoulet (I'm >> > eating the leftover cassoulet this instant... it holds up nicely) and >> > we noted that the entire population of the planet could live like >> > this, if people weren't such jerks. >> >> How would that work exactly? How are you going to pay the person who >> collects your garbage or serves you those oysters the same as what you >> make? Sounds very socialistic to me. >> >> -- >> >> Rick C > >Why are we wealthier than the cavemen? We both started with the same >raw materials (and in fact they had them arguably greater abundance, >since none of them had been used). So why? > >The answer lies in our accumulated knowledge, and our codes of conduct, >with the latter a /sine qua non/ for the former. > >But socialistic codes of conduct have a poor history for creating wealth. >Rather, they prey on wealth once it exists, dragging it down. > >"There is in fact a manly and legitimate passion for equality that spurs > all men to wish to be strong and esteemed. This passion tends to elevate > the lesser to the rank of the greater. But one also finds in the human > heart a depraved taste for equality, which impels the weak to want to > bring the strong down to their level, and which reduces men to preferring > equality in servitude to inequality in freedom." > > --Alexis de Tocqueville, Ancien Regime and the Revolution > >Cheers, >James Arthur
You're whetting my appetite... time to re-read de Tocqueville, Mill, Rousseau and Burke. (I wanted to name our first son John Stuart, so we settled on Aaron David ;-) ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I'm looking for work... see my website.
On Tue, 12 Jul 2016 13:48:32 -0700 (PDT), dagmargoodboat@yahoo.com
wrote:

>On Tuesday, July 12, 2016 at 3:14:43 PM UTC-4, rickman wrote: >> On 7/12/2016 3:08 PM, John Larkin wrote: >> > >> > Mo and I were sitting at a table near the window of our neighborhood >> > French restaurant snacking on beer and oysters and cassoulet (I'm >> > eating the leftover cassoulet this instant... it holds up nicely) and >> > we noted that the entire population of the planet could live like >> > this, if people weren't such jerks. >> >> How would that work exactly? How are you going to pay the person who >> collects your garbage or serves you those oysters the same as what you >> make? Sounds very socialistic to me. >> >> -- >> >> Rick C > >Why are we wealthier than the cavemen? We both started with the same >raw materials (and in fact they had them arguably greater abundance, >since none of them had been used). So why? > >The answer lies in our accumulated knowledge, and our codes of conduct, >with the latter a /sine qua non/ for the former. > >But socialistic codes of conduct have a poor history for creating wealth. >Rather, they prey on wealth once it exists, dragging it down. > >"There is in fact a manly and legitimate passion for equality that spurs > all men to wish to be strong and esteemed. This passion tends to elevate > the lesser to the rank of the greater. But one also finds in the human > heart a depraved taste for equality, which impels the weak to want to > bring the strong down to their level, and which reduces men to preferring > equality in servitude to inequality in freedom." > > --Alexis de Tocqueville, Ancien Regime and the Revolution > >Cheers, >James Arthur
Even a modern socialist train wreck like Cuba or Venezuela is better than a primitive society whose favorite pastime is tribal warfare. The socialists still have mail service, so can always get by on remittences from the USA. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Den tirsdag den 12. juli 2016 kl. 23.56.53 UTC+2 skrev John Larkin:
> On Tue, 12 Jul 2016 13:48:32 -0700 (PDT), dagmargoodboat@yahoo.com > wrote: > > >On Tuesday, July 12, 2016 at 3:14:43 PM UTC-4, rickman wrote: > >> On 7/12/2016 3:08 PM, John Larkin wrote: > >> > > >> > Mo and I were sitting at a table near the window of our neighborhood > >> > French restaurant snacking on beer and oysters and cassoulet (I'm > >> > eating the leftover cassoulet this instant... it holds up nicely) and > >> > we noted that the entire population of the planet could live like > >> > this, if people weren't such jerks. > >> > >> How would that work exactly? How are you going to pay the person who > >> collects your garbage or serves you those oysters the same as what you > >> make? Sounds very socialistic to me. > >> > >> -- > >> > >> Rick C > > > >Why are we wealthier than the cavemen? We both started with the same > >raw materials (and in fact they had them arguably greater abundance, > >since none of them had been used). So why? > > > >The answer lies in our accumulated knowledge, and our codes of conduct, > >with the latter a /sine qua non/ for the former. > > > >But socialistic codes of conduct have a poor history for creating wealth. > >Rather, they prey on wealth once it exists, dragging it down. > > > >"There is in fact a manly and legitimate passion for equality that spurs > > all men to wish to be strong and esteemed. This passion tends to elevate > > the lesser to the rank of the greater. But one also finds in the human > > heart a depraved taste for equality, which impels the weak to want to > > bring the strong down to their level, and which reduces men to preferring > > equality in servitude to inequality in freedom." > > > > --Alexis de Tocqueville, Ancien Regime and the Revolution > > > >Cheers, > >James Arthur > > Even a modern socialist train wreck like Cuba or Venezuela is better > than a primitive society whose favorite pastime is tribal warfare. >
https://youtu.be/tA3L7RG8bnA
On Tuesday, July 12, 2016 at 9:09:07 PM UTC+2, John Larkin wrote:
> On Tue, 12 Jul 2016 10:51:20 -0700 (PDT), dagmargoodboat@yahoo.com > wrote: > > >On Tuesday, July 12, 2016 at 11:50:24 AM UTC-4, Lasse Langwadt Christensen wrote: > >> Den tirsdag den 12. juli 2016 kl. 17.41.01 UTC+2 skrev rickman: > >> > On 7/12/2016 9:44 AM, Phil Hobbs wrote: > >> > > On 07/10/2016 08:38 PM, M Philbrook wrote: > >> > > > >> > >>> > >> > >> You know what they say John, misery loves company! > >> > > > >> > > As an aside, that's an instance where a sarcastic twist on an old saw > >> > > has taken over from the original meaning, which of course was, > >> > > > >> > > "People who are sad or in trouble feel better if you go visit them." > >> > > >> > I didn't see a smiley so I have to assume you are serious. That's not > >> > what it means. It means we find it hard to be sympathetic when we are > >> > miserable and have little pity for others. Or, seeing others as > >> > miserable as ourselves makes us feel better. > >> > > >> > I heard a report on the radio the other day that essentially said this. > >> > We don't measure our life situation in absolute terms, rather in > >> > relative terms compared to those around us. > >> > >> that explains the popularity of reality shows with dumb people and > >> dysfunctional families > >> > >> -Lasse > > > >I think it accounts for political differences too. > > > >"The French want no-one to be their superior. The English want inferiors. > > The Frenchman constantly raises his eyes above him with anxiety. The > > Englishman lowers his beneath him with satisfaction." > > --Alexis de Tocqueville > > > >But I measure my life in absolute terms, not against what others have. > >If I'm warm, with enough to eat, I'm happy! And when I do measure > >against others, I find tremendous bounty in what others scorn-- > > > > the poorest American can buy strawberries out of season, bananas from > >Honduras, kiwis from God knows where, has a car, an air conditioner, > >a cell phone, and a TV. 100 years ago, no king had any of those. > > > >Too many people worry not that they have enough, but that someone else > >has more. > > > >We truly live like kings. No--better.
Kings didn't actually live comfortably. They lived impressively, which isn't necessarily the same thing.
> Mo and I were sitting at a table near the window of our neighborhood > French restaurant snacking on beer and oysters and cassoulet (I'm > eating the leftover cassoulet this instant... it holds up nicely) and > we noted that the entire population of the planet could live like > this, if people weren't such jerks.
You've not only got enough to eat, but somebody else cooked it for you. Everybody he entire planet could have enough to eat, but it would require a more complicated political re-organisation than is implied by "if people weren't such jerks". Having somebody else cook the food for everybody on the planet would be a little more complicated.
> The average person in a developed country does live better than Henry > 8th or Louis 14th. I bet the beer and wine at 7-11 is better than > anything they had.
Henry the 8th seems to have die from complications of obesity - like many Americans today. Medical science may manage the complications better today, but it hasn't solved the problem of people eating themselves to death. Louis the 14th lived a very public life - even his getting out bed in the morning was a choreographed ceremony. The wine he drank was probably as good as anything you can buy today - a lot of the wine sold to the palace would have been rubbish, but the royal caterers would have passed off all but the very best to lesser dignitaries. 7-11 doesn't stock the high quality wines that I drink, and it certainly doesn't stock the wines from the vineyards that were famously good back in Henry the 14th's day, and still command premium prices today, if you can find a wine merchant who stocks them. "Living like a king" is one of those sayings that doesn't bear much examination. Kings still get assassinated - though less often than they used to. -- Bill Sloman, Sydney
On Sun, 10 Jul 2016 17:15:51 -0400, rickman <gnuarm@gmail.com> wrote:

>On 7/10/2016 5:01 PM, John Fields wrote: >> On Thu, 23 Jun 2016 22:49:35 -0400, krw <krw@nowhere.com> wrote: >> >>> On Thu, 23 Jun 2016 21:07:54 -0500, Tim Wescott <tim@seemywebsite.com> >>> wrote: >>> >>>> On Thu, 23 Jun 2016 16:20:27 -0700, Jim Thompson wrote: >>>> >>>>> On Thu, 23 Jun 2016 17:42:40 -0500, Tim Wescott >>>>> <seemywebsite@myfooter.really> wrote: >>>>> >>>>>> I know the theory, more or less. >>>>>> >>>>>> In practice, what's the reverse current through a zener diode at levels >>>>>> well below the breakdown voltage? I've got a circuit where I'm feeding >>>>>> a 12V linear regulator with a 25V line. It would be handy to put a >>>>>> zener diode in there so that when the 25V line drops to 4V the current >>>>>> into the regulator drops to tens of microamps. I'm wondering if a >>>>>> series zener will do it. >>>>> >>>>> Clear as mud ;-) Post a schematic of what you mean... 25V -> 4V ?? >>>>> >>>>> ...Jim Thompson >>>> >>>> Sorry. When the circuit is nominally on I want to make 12V from the 25V >>>> rail with a linear regulator. When the circuit is nominally off the 25V >>>> rail is at 4V, and I would like to effectively shut off the 12V line >>>> entirely. >>>> >>>> A 6.8V zener would make for around 18V at the input to the regulator, so >>>> the "on" part works fine. I'm just wondering if, with 4V on one side and >>>> a regulator input on the other, if the zener will flow some predictably >>>> low current. >>> >>> 6.8V zeners suck. I'd just use an enable pin on the regulator.
--- Actually, raw 6.8 volt Zeners pretty much rule in terms of voltage tempco, so they don't suck as much as you claim. ---
>> And if the regulator of choice has no ENABLE pin, then what? > >Then "choise" another regulator... There is no shortage of suitable >regulators in spite of the inability of some people to find them.
--- "Choise"??? ---
>>> Some have an accurate reference so you can program the dropout voltage with >>> just a voltage divider. When the input drops below that value, the >>> regulator shuts off (see: UVLO - Under Voltage Lock Out). >> >> --- >> Wescott was obviously referring to a three terminal series regulator, >> so your rsponse is irrelevant. >> >> As to your damnation of 6.8 volt Zeners, 6.8 volts is pretty close to >> where, with the specified reverse current through the diode, the >> Zener's tempco goes away, so why would you think 6.8 volt Zeners suck? > >If someone wants to limit themselves to unsuitable regulators, then it >can be hard to help them with electronics design. Tim is willing to >consider regulators with an enable, but he can't see to get past the >limitations of the Digikey selection tool. I recommend starting with >the TI tool on their web site. It's easier to find a part on their site >that meets the requirements.
Rather than damning one tool and blessing another, wouldn't it be better to teach a man how to fish?
On Sun, 10 Jul 2016 14:40:27 -0700, John Larkin
<jjlarkin@highlandtechnology.com> wrote:

>On Sun, 10 Jul 2016 16:01:50 -0500, John Fields ><jfields@austininstruments.com> wrote: > >>On Thu, 23 Jun 2016 22:49:35 -0400, krw <krw@nowhere.com> wrote: >> >>>On Thu, 23 Jun 2016 21:07:54 -0500, Tim Wescott <tim@seemywebsite.com> >>>wrote: >>> >>>>On Thu, 23 Jun 2016 16:20:27 -0700, Jim Thompson wrote: >>>> >>>>> On Thu, 23 Jun 2016 17:42:40 -0500, Tim Wescott >>>>> <seemywebsite@myfooter.really> wrote: >>>>> >>>>>>I know the theory, more or less. >>>>>> >>>>>>In practice, what's the reverse current through a zener diode at levels >>>>>>well below the breakdown voltage? I've got a circuit where I'm feeding >>>>>>a 12V linear regulator with a 25V line. It would be handy to put a >>>>>>zener diode in there so that when the 25V line drops to 4V the current >>>>>>into the regulator drops to tens of microamps. I'm wondering if a >>>>>>series zener will do it. >>>>> >>>>> Clear as mud ;-) Post a schematic of what you mean... 25V -> 4V ?? >>>>> >>>>> ...Jim Thompson >>>> >>>>Sorry. When the circuit is nominally on I want to make 12V from the 25V >>>>rail with a linear regulator. When the circuit is nominally off the 25V >>>>rail is at 4V, and I would like to effectively shut off the 12V line >>>>entirely. >>>> >>>>A 6.8V zener would make for around 18V at the input to the regulator, so >>>>the "on" part works fine. I'm just wondering if, with 4V on one side and >>>>a regulator input on the other, if the zener will flow some predictably >>>>low current. >>> >>>6.8V zeners suck. I'd just use an enable pin on the regulator. >> >>And if the regulator of choice has no ENABLE pin, then what? >> >>>Some have an accurate reference so you can program the dropout voltage with >>>just a voltage divider. When the input drops below that value, the >>>regulator shuts off (see: UVLO - Under Voltage Lock Out). >> >>--- >>Wescott was obviously referring to a three terminal series regulator, >>so your rsponse is irrelevant. >> >>As to your damnation of 6.8 volt Zeners, 6.8 volts is pretty close to >>where, with the specified reverse current through the diode, the >>Zener's tempco goes away, so why would you think 6.8 volt Zeners suck? >> >>John Fields > >Good grief, you only post here to be deliberately obnoxious. What a >sucky way to live.
--- Au contraire. Instead of just flapping your gums, as usual, why don't you state what technical quarrels you have with a 6.8 volt Zener diode, properly biased, having close to zero TC? JF
Den onsdag den 27. juli 2016 kl. 21.29.30 UTC+2 skrev John Fields:
> On Sun, 10 Jul 2016 14:40:27 -0700, John Larkin > <jjlarkin@highlandtechnology.com> wrote: > > >On Sun, 10 Jul 2016 16:01:50 -0500, John Fields > ><jfields@austininstruments.com> wrote: > > > >>On Thu, 23 Jun 2016 22:49:35 -0400, krw <krw@nowhere.com> wrote: > >> > >>>On Thu, 23 Jun 2016 21:07:54 -0500, Tim Wescott <tim@seemywebsite.com> > >>>wrote: > >>> > >>>>On Thu, 23 Jun 2016 16:20:27 -0700, Jim Thompson wrote: > >>>> > >>>>> On Thu, 23 Jun 2016 17:42:40 -0500, Tim Wescott > >>>>> <seemywebsite@myfooter.really> wrote: > >>>>> > >>>>>>I know the theory, more or less. > >>>>>> > >>>>>>In practice, what's the reverse current through a zener diode at levels > >>>>>>well below the breakdown voltage? I've got a circuit where I'm feeding > >>>>>>a 12V linear regulator with a 25V line. It would be handy to put a > >>>>>>zener diode in there so that when the 25V line drops to 4V the current > >>>>>>into the regulator drops to tens of microamps. I'm wondering if a > >>>>>>series zener will do it. > >>>>> > >>>>> Clear as mud ;-) Post a schematic of what you mean... 25V -> 4V ?? > >>>>> > >>>>> ...Jim Thompson > >>>> > >>>>Sorry. When the circuit is nominally on I want to make 12V from the 25V > >>>>rail with a linear regulator. When the circuit is nominally off the 25V > >>>>rail is at 4V, and I would like to effectively shut off the 12V line > >>>>entirely. > >>>> > >>>>A 6.8V zener would make for around 18V at the input to the regulator, so > >>>>the "on" part works fine. I'm just wondering if, with 4V on one side and > >>>>a regulator input on the other, if the zener will flow some predictably > >>>>low current. > >>> > >>>6.8V zeners suck. I'd just use an enable pin on the regulator. > >> > >>And if the regulator of choice has no ENABLE pin, then what? > >> > >>>Some have an accurate reference so you can program the dropout voltage with > >>>just a voltage divider. When the input drops below that value, the > >>>regulator shuts off (see: UVLO - Under Voltage Lock Out). > >> > >>--- > >>Wescott was obviously referring to a three terminal series regulator, > >>so your rsponse is irrelevant. > >> > >>As to your damnation of 6.8 volt Zeners, 6.8 volts is pretty close to > >>where, with the specified reverse current through the diode, the > >>Zener's tempco goes away, so why would you think 6.8 volt Zeners suck? > >> > >>John Fields > > > >Good grief, you only post here to be deliberately obnoxious. What a > >sucky way to live. > > --- > Au contraire. > > Instead of just flapping your gums, as usual, why don't you state what > technical quarrels you have with a 6.8 volt Zener diode, properly > biased, having close to zero TC? >
looking at a few datasheets, zero TC is ~5.6V, lowest impedance ~6.8V -Lasse
On Sun, 10 Jul 2016 17:58:29 -0400, krw@attt.bizz wrote:

>On Sun, 10 Jul 2016 16:01:50 -0500, John Fields ><jfields@austininstruments.com> wrote: > >>On Thu, 23 Jun 2016 22:49:35 -0400, krw <krw@nowhere.com> wrote: >> >>>On Thu, 23 Jun 2016 21:07:54 -0500, Tim Wescott <tim@seemywebsite.com> >>>wrote: >>> >>>>On Thu, 23 Jun 2016 16:20:27 -0700, Jim Thompson wrote: >>>> >>>>> On Thu, 23 Jun 2016 17:42:40 -0500, Tim Wescott >>>>> <seemywebsite@myfooter.really> wrote: >>>>> >>>>>>I know the theory, more or less. >>>>>> >>>>>>In practice, what's the reverse current through a zener diode at levels >>>>>>well below the breakdown voltage? I've got a circuit where I'm feeding >>>>>>a 12V linear regulator with a 25V line. It would be handy to put a >>>>>>zener diode in there so that when the 25V line drops to 4V the current >>>>>>into the regulator drops to tens of microamps. I'm wondering if a >>>>>>series zener will do it. >>>>> >>>>> Clear as mud ;-) Post a schematic of what you mean... 25V -> 4V ?? >>>>> >>>>> ...Jim Thompson >>>> >>>>Sorry. When the circuit is nominally on I want to make 12V from the 25V >>>>rail with a linear regulator. When the circuit is nominally off the 25V >>>>rail is at 4V, and I would like to effectively shut off the 12V line >>>>entirely. >>>> >>>>A 6.8V zener would make for around 18V at the input to the regulator, so >>>>the "on" part works fine. I'm just wondering if, with 4V on one side and >>>>a regulator input on the other, if the zener will flow some predictably >>>>low current. >>> >>>6.8V zeners suck. I'd just use an enable pin on the regulator. >> >>And if the regulator of choice has no ENABLE pin, then what? > >Then choose another, asshole.
--- That's no help, since hostility leads, reductio ad absurdum, to war. Do you want to declare war with your limited resources? ---
>When you want to discuss electronics, let us all know.
--- I'm always up for that, but your invitation is preumptuous, as if you were running the game. JF
On Wed, 27 Jul 2016 14:49:40 -0500, John Fields
<jfields@austininstruments.com> wrote:

>On Sun, 10 Jul 2016 17:58:29 -0400, krw@attt.bizz wrote: >
[snip]
>> >>Then choose another, asshole. > >--- >That's no help, since hostility leads, reductio ad absurdum, to war. > >Do you want to declare war with your limited resources? >--- > >>When you want to discuss electronics, let us all know. > >--- >I'm always up for that, but your invitation is preumptuous, as if you >were running the game. > >JF
krw stole that line from Larkin... neither are running the game... just seeking attention for their competency-starved egos. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I'm looking for work... see my website.
On Wed, 27 Jul 2016 14:49:40 -0500, John Fields
<jfields@austininstruments.com> wrote:

>On Sun, 10 Jul 2016 17:58:29 -0400, krw@attt.bizz wrote: > >>On Sun, 10 Jul 2016 16:01:50 -0500, John Fields >><jfields@austininstruments.com> wrote: >> >>>On Thu, 23 Jun 2016 22:49:35 -0400, krw <krw@nowhere.com> wrote: >>> >>>>On Thu, 23 Jun 2016 21:07:54 -0500, Tim Wescott <tim@seemywebsite.com> >>>>wrote: >>>> >>>>>On Thu, 23 Jun 2016 16:20:27 -0700, Jim Thompson wrote: >>>>> >>>>>> On Thu, 23 Jun 2016 17:42:40 -0500, Tim Wescott >>>>>> <seemywebsite@myfooter.really> wrote: >>>>>> >>>>>>>I know the theory, more or less. >>>>>>> >>>>>>>In practice, what's the reverse current through a zener diode at levels >>>>>>>well below the breakdown voltage? I've got a circuit where I'm feeding >>>>>>>a 12V linear regulator with a 25V line. It would be handy to put a >>>>>>>zener diode in there so that when the 25V line drops to 4V the current >>>>>>>into the regulator drops to tens of microamps. I'm wondering if a >>>>>>>series zener will do it. >>>>>> >>>>>> Clear as mud ;-) Post a schematic of what you mean... 25V -> 4V ?? >>>>>> >>>>>> ...Jim Thompson >>>>> >>>>>Sorry. When the circuit is nominally on I want to make 12V from the 25V >>>>>rail with a linear regulator. When the circuit is nominally off the 25V >>>>>rail is at 4V, and I would like to effectively shut off the 12V line >>>>>entirely. >>>>> >>>>>A 6.8V zener would make for around 18V at the input to the regulator, so >>>>>the "on" part works fine. I'm just wondering if, with 4V on one side and >>>>>a regulator input on the other, if the zener will flow some predictably >>>>>low current. >>>> >>>>6.8V zeners suck. I'd just use an enable pin on the regulator. >>> >>>And if the regulator of choice has no ENABLE pin, then what? >> >>Then choose another, asshole. > >--- >That's no help, since hostility leads, reductio ad absurdum, to war. > >Do you want to declare war with your limited resources? >--- > >>When you want to discuss electronics, let us all know. > >--- >I'm always up for that, but your invitation is preumptuous, as if you >were running the game. > >JF
That's silly. I'm running the game. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com