Forums

Zener diode modeling

Started by Robert Baer December 31, 2011
Jim Thompson wrote:
> On Fri, 30 Dec 2011 20:49:20 -0800, Robert Baer > <robertbaer@localnet.com> wrote: > >> Say one takes an E-B junction of a transistor or other diode and >> measures the (reverse) breakdown voltage over a wide range of currents >> (say 5nA to 5mA), and assume there is no point or range where one sees >> characteristics of negative resistance or of oscillation. >> Also say that voltage is about 9 volts. >> Q: is that zener or avalanche breakdown? > > Both phenomenon are present in any diode. Below ~5.6V breakdown is > predominately Zener effect, above ~5.6V, predominately avalanche > breakdown. > >> Q: how does one make a SPICE model of such a proposed beastie? > > Accurately? Not easily. Spice has BV and IBV terms in the diode > model. Some simulators, such as PSpice, support the Mextram BJT model > which models avalanche in the _collector_: > > http://www.semiconductors.philips.com/Philips_Models/bipolar/mextram/ > > Comes up as 404, but cross-references some links. > > Off-the-top-of-my-head I don't know of a BJT model which covers the > B-E junction during breakdown. Pasting a parallel diode with BV and > IBV roughly covers the problem, but doesn't model the true effects > that occur in the base region. > > In much of the high-speed BJT (I/C) world, reverse-bias of the B-E > junction is forbidden above ~2-4V due to it causing doping migration > and ultimate device failure. > > Here is what I use as a parameterized model for zeners that have no > manufacturer's model... > > **** > .SUBCKT MyZENER 1 2 PARAMS: BV=10 IBV=1m RS=1 IS=10f CJO=10pF > D1 1 2 DZ > .MODEL DZ D( > + IS = {IS} > + RS = {RS} > + N = 1 > + EG = 1.11 > + BV = {BV} > + IBV = {IBV} > + CJO = {CJO} > + VJ = 0.75 > + M = 0.33 ) > .ENDS MyZENER > **** > > ...Jim Thompson
Thanks for that model; will play with it. Which of those NXP BF?? transistors or diodes (big list i see) would be "closest" to the E-B of a 2N3904?
On Jan 1, 8:15=A0am, Robert Baer <robertb...@localnet.com> wrote:
> BillSlomanwrote: > > On Dec 31, 5:49 am, Robert Baer <robertb...@localnet.com> wrote: > >> =A0 =A0Say one takes an E-B junction of a transistor or other diode an=
d
> >> measures the (reverse) breakdown voltage over a wide range of currents > >> (say 5nA to 5mA), and assume there is no point or range where one sees > >> characteristics of negative resistance or of oscillation. > >> =A0 =A0Also say that voltage is about 9 volts. > >> =A0 =A0Q: is that zener or avalanche breakdown? > >> =A0 =A0Q: how does one make a SPICE model of such a proposed beastie? > > > At nine volts, the breakdown is by avalanche. > > > It happens in very small areas, and the transit times is picoseconds, > > so at low currents the avalanche self-extinguishes from time to time > > due to the statistical fluctuations in avalanche multiplication > > process - sometimes a charge carrier gets through the avalanche region > > without generating any new charge-carrier pairs. > > > This isn't easy to model in Spice - it probably needs a current- > > controlled random noise generator, but the real noise looks more like > > a series of Dirac spikes. > > > For added extra complexity, you can throw in the fact that the > > avalanche process generates light, and in glass-packaged zener diodes > > this can trigger other avalanches. > > > There was a thread on the subject here, many years ago - "Zener diode > > oscillation" from July 7, 1997. > > 1) What about (say) 8.2 volts?
The cross-over point is around 4.7V IIRR - the temperature coefficient of the break-down voltage is the clue, because it is negative when the Zener mechanism is dominant, and postive when avalanche breakdown is dominant http://www.datasheetcatalog.org/datasheet/nationalsemiconductor/DS013023.PD= F
> 2) How would one go about accessing that 1997 thread?
Got to groups.google.com and click on "advanced search". Searching on the exact phrase ""Zener diode oscillation" will do it. -- Bill Sloman, Nijmegen
On Jan 1, 8:21=A0am, Robert Baer <robertb...@localnet.com> wrote:
> Jamie wrote: > > Robert Baer wrote: > >> =A0 Say one takes an E-B junction of a transistor or other diode and > >> measures the (reverse) breakdown voltage over a wide range of currents > >> (say 5nA to 5mA), and assume there is no point or range where one sees > >> characteristics of negative resistance or of oscillation. > >> =A0 Also say that voltage is about 9 volts. > >> =A0 Q: is that zener or avalanche breakdown? > >> =A0 Q: how does one make a SPICE model of such a proposed beastie? > > > =A0 For negative voltage I do think the voltage needs to be up around > > 12 volts. Min of 10.5 the last time I experimented with that. > > > =A0 But this was all at the bench since LTspice can't sim that and I > > =A0operated a LED flashing for quit some time to test if the beta > > was lose its punch.. It seem to survive the test. > > > =A0 And I did it with a 2n2222 if that makes any difference. I also > > noticed with a another batch of 2222's from a different SI maker, it > > would not work at all, unless the voltage range was different? > > > =A0Jamie > > =A0 =A0As far as a given type (2N2222, 2N3904, etc etc & etc), every > manufacturer of a given type will produce a transistor with different > reverse E-B characteristics - and those characteristics can suddenly > change with zero notice. > =A0 =A0Note the E-B breakdown is "off the data sheet"; lotta so-called > quotes are "5V" and you will never find a (silicon small signal) > transistor below 7V.
Unless it is a wide bandwidth part http://www.nxp.com/documents/data_sheet/BFT92_CNV.pdf They do seem to have a thin base. -- Bill Sloman, Nijmegen
On Sat, 31 Dec 2011 23:38:02 -0800, Robert Baer
<robertbaer@localnet.com> wrote:

>Jim Thompson wrote: >> On Fri, 30 Dec 2011 20:49:20 -0800, Robert Baer >> <robertbaer@localnet.com> wrote: >> >>> Say one takes an E-B junction of a transistor or other diode and >>> measures the (reverse) breakdown voltage over a wide range of currents >>> (say 5nA to 5mA), and assume there is no point or range where one sees >>> characteristics of negative resistance or of oscillation. >>> Also say that voltage is about 9 volts. >>> Q: is that zener or avalanche breakdown? >> >> Both phenomenon are present in any diode. Below ~5.6V breakdown is >> predominately Zener effect, above ~5.6V, predominately avalanche >> breakdown. >> >>> Q: how does one make a SPICE model of such a proposed beastie? >> >> Accurately? Not easily. Spice has BV and IBV terms in the diode >> model. Some simulators, such as PSpice, support the Mextram BJT model >> which models avalanche in the _collector_: >> >> http://www.semiconductors.philips.com/Philips_Models/bipolar/mextram/ >> >> Comes up as 404, but cross-references some links. >> >> Off-the-top-of-my-head I don't know of a BJT model which covers the >> B-E junction during breakdown. Pasting a parallel diode with BV and >> IBV roughly covers the problem, but doesn't model the true effects >> that occur in the base region. >> >> In much of the high-speed BJT (I/C) world, reverse-bias of the B-E >> junction is forbidden above ~2-4V due to it causing doping migration >> and ultimate device failure. >> >> Here is what I use as a parameterized model for zeners that have no >> manufacturer's model... >> >> **** >> .SUBCKT MyZENER 1 2 PARAMS: BV=10 IBV=1m RS=1 IS=10f CJO=10pF >> D1 1 2 DZ >> .MODEL DZ D( >> + IS = {IS} >> + RS = {RS} >> + N = 1 >> + EG = 1.11 >> + BV = {BV} >> + IBV = {IBV} >> + CJO = {CJO} >> + VJ = 0.75 >> + M = 0.33 ) >> .ENDS MyZENER >> **** >> >> ...Jim Thompson > Thanks for that model; will play with it. > Which of those NXP BF?? transistors or diodes (big list i see) would >be "closest" to the E-B of a 2N3904?
Best way to match E-B break-down equivalency is to match BVceo's. Any other differences are size-related rather than doping. ...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.
On Dec 31 2011, 4:24=A0am, Bill Sloman <bill.slo...@ieee.org> wrote:
> On Dec 31, 5:49=A0am, Robert Baer <robertb...@localnet.com> wrote: > > > =A0 =A0Say one takes an E-B junction of a transistor or other diode and > > measures the (reverse) breakdown voltage over a wide range of currents > > (say 5nA to 5mA), and assume there is no point or range where one sees > > characteristics of negative resistance or of oscillation. > > =A0 =A0Also say that voltage is about 9 volts. > > =A0 =A0Q: is that zener or avalanche breakdown? > > =A0 =A0Q: how does one make a SPICE model of such a proposed beastie? > > At nine volts, the breakdown is by avalanche. > > It happens in very small areas, and the transit times is picoseconds, > so at low currents the avalanche self-extinguishes from time to time > due to the statistical fluctuations in avalanche multiplication > process - sometimes a charge carrier gets through the avalanche region > without generating any new charge-carrier pairs. > > This isn't easy to model in Spice - it probably needs a current- > controlled random noise generator, but the real noise looks more like > a series of Dirac spikes.
It's even 'worse' than that. The noise changes 'character' as a function of current. Right near the 'knee' you go from random pulses to random steps. (random telegraph noise). With more noise at low frequency.... But I'm not sure it's 1/f.
> > For added extra complexity, you can throw in the fact that the > avalanche process generates light, and in glass-packaged zener diodes > this can trigger other avalanches.
And that room light can get in and 'modulate' the avalanche.
> > There was a thread on the subject here, many years ago - "Zener diode > oscillation" from July 7, 1997. >
Yeah nice thread. I find that for use as noise sources it's best to keep the current below the knee. George H.
> -- > Bill Sloman, Nijmegen > > -- > Bill Sloman, Nijmegen
On Sun, 1 Jan 2012 08:57:38 -0800 (PST), George Herold
<gherold@teachspin.com> wrote:

>On Dec 31 2011, 4:24&#2013266080;am, Bill Sloman <bill.slo...@ieee.org> wrote: >> On Dec 31, 5:49&#2013266080;am, Robert Baer <robertb...@localnet.com> wrote: >> >> > &#2013266080; &#2013266080;Say one takes an E-B junction of a transistor or other diode and >> > measures the (reverse) breakdown voltage over a wide range of currents >> > (say 5nA to 5mA), and assume there is no point or range where one sees >> > characteristics of negative resistance or of oscillation. >> > &#2013266080; &#2013266080;Also say that voltage is about 9 volts. >> > &#2013266080; &#2013266080;Q: is that zener or avalanche breakdown? >> > &#2013266080; &#2013266080;Q: how does one make a SPICE model of such a proposed beastie? >> >> At nine volts, the breakdown is by avalanche. >> >> It happens in very small areas, and the transit times is picoseconds, >> so at low currents the avalanche self-extinguishes from time to time >> due to the statistical fluctuations in avalanche multiplication >> process - sometimes a charge carrier gets through the avalanche region >> without generating any new charge-carrier pairs. >> >> This isn't easy to model in Spice - it probably needs a current- >> controlled random noise generator, but the real noise looks more like >> a series of Dirac spikes. > >It's even 'worse' than that. The noise changes 'character' as a >function of current. >Right near the 'knee' you go from random pulses to random steps. >(random telegraph noise). With more noise at low frequency.... But >I'm not sure it's 1/f.
"Popcorn" noise... often seen in bipolar OpAmp input stages.
> > >> >> For added extra complexity, you can throw in the fact that the >> avalanche process generates light, and in glass-packaged zener diodes >> this can trigger other avalanches. > >And that room light can get in and 'modulate' the avalanche. >> >> There was a thread on the subject here, many years ago - "Zener diode >> oscillation" from July 7, 1997. >> > >Yeah nice thread. > >I find that for use as noise sources it's best to keep the current >below the knee. > >George H. >> -- >> Bill Sloman, Nijmegen >> >> -- >> Bill Sloman, Nijmegen
...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.
On Jan 1, 6:17=A0pm, Jim Thompson <To-Email-Use-The-Envelope-I...@On-My-
Web-Site.com> wrote:
> On Sun, 1 Jan 2012 08:57:38 -0800 (PST), George Herold > > > > > > > > > > <gher...@teachspin.com> wrote: > >On Dec 31 2011, 4:24=A0am,BillSloman<bill.slo...@ieee.org> wrote: > >> On Dec 31, 5:49=A0am, Robert Baer <robertb...@localnet.com> wrote: > > >> > =A0 =A0Say one takes an E-B junction of a transistor or other diode =
and
> >> > measures the (reverse) breakdown voltage over a wide range of curren=
ts
> >> > (say 5nA to 5mA), and assume there is no point or range where one se=
es
> >> > characteristics of negative resistance or of oscillation. > >> > =A0 =A0Also say that voltage is about 9 volts. > >> > =A0 =A0Q: is that zener or avalanche breakdown? > >> > =A0 =A0Q: how does one make a SPICE model of such a proposed beastie=
?
> > >> At nine volts, the breakdown is by avalanche. > > >> It happens in very small areas, and the transit times is picoseconds, > >> so at low currents the avalanche self-extinguishes from time to time > >> due to the statistical fluctuations in avalanche multiplication > >> process - sometimes a charge carrier gets through the avalanche region > >> without generating any new charge-carrier pairs. > > >> This isn't easy to model in Spice - it probably needs a current- > >> controlled random noise generator, but the real noise looks more like > >> a series of Dirac spikes. > > >It's even 'worse' than that. =A0The noise changes 'character' as a > >function of current. > >Right near the 'knee' you go from random pulses to random steps. > >(random telegraph noise). =A0With more noise at low frequency.... But > >I'm not sure it's 1/f. > > "Popcorn" noise... often seen in bipolar OpAmp input stages.
Which isn't 1/f either, but probably reflects rather different physical process. http://en.wikipedia.org/wiki/Burst_noise The random trapping and release of charge carriers at thin film interfaces or at defect sites in bulk semiconductor crystal could be happening in an avalanching diode, but people who talk about avalanche zener diodes as noise sources don't seem to find it necessary to invoke this particular mechanism. -- Bill Sloman, Nijmegen
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Phil Allison wrote:
> "Robert Baer" >=20 >>> ** Start here: >>> >>> http://en.wikipedia.org/wiki/Zener_diode >>> >>> Do not pass GO, do not collect $200. >>> >>> >> OK; the temperature coefficient is positive, so by WikiPedia "avalan=
che=20
>> effect .. exhibits a positive temperature coefficient", as well as "ab=
ove=20
>> 5.6 volts, the avalanche effect becomes predominant". >> And that is exactly what i thought.. >=20 > ** Yawnnnnnnnnnnnnnnnnnn.... >=20 >=20 >> I thought that diodes working in the avalanche region would NOT act i=
n a=20
>> monotonically increasing voltage VS current manner - especially over s=
uch=20
>> a wide current range. >=20 > ** You were expecting to see a tunnel diode effect ? >=20 >=20 >> The I-V curve indicates a zener mode, the negative TC indicates avala=
nche=20
>> type .. >=20 >=20 > ** Both statements are wrong. >=20 > FFS learn to read. >=20 >=20 >> So...i pete the questions again. >=20 > ** Who cares.
I'm guessing that Maturity wasn't on your New Year's resolution list. Grow up. mike --------------enig0B092DE3CB57D9F8E51C6BE2 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.18 (GNU/Linux) iQEbBAEBAgAGBQJPAKcWAAoJECGtZwCbtgwXZRIH91jMBvAxL6j8FK01hV4RGYNZ JnRZd5z1pacS5OkN8fAHD3xPLQ9Aa4DGlEpZEJRhgzK9rT+t4TbguujAcoRM35PE v6sRRSOB+qosmprexyNivpfH68mbkqJfzjbLGtlviqlVTGAQZsfzzFdpQe5MZxMd hQ2/eEHA+sBAfC+tI1ZKf+68pKAIfg0av/11EXGuVg4A0YjaYvjOfVdJ3/NrJr3M hhgvVLLl9Dk6wZo7M2MdBjrjn/e0yJQ+JdM1fb1WN0ws2+EA/mMKrh47mZ6qKBdD QdXQuTy/9ZbEmYHsHyL0NI6NtWXN0DNTkDK+05oymtq86ESfTjlngXDqK2VNPg== =TlRK -----END PGP SIGNATURE----- --------------enig0B092DE3CB57D9F8E51C6BE2--
Phil Allison wrote:
> "Robert Baer" > >>> ** Start here: >>> >>> http://en.wikipedia.org/wiki/Zener_diode >>> >>> Do not pass GO, do not collect $200. >>> >>> >> OK; the temperature coefficient is positive, so by WikiPedia "avalanche >> effect .. exhibits a positive temperature coefficient", as well as "above >> 5.6 volts, the avalanche effect becomes predominant". >> And that is exactly what i thought.. > > ** Yawnnnnnnnnnnnnnnnnnn.... > > >> I thought that diodes working in the avalanche region would NOT act in a >> monotonically increasing voltage VS current manner - especially over such >> a wide current range. > > ** You were expecting to see a tunnel diode effect ?
* I have seen oscillation as well as negative resistance regions (and both), not unlike what one sees with a tunnel diode.
> > >> The I-V curve indicates a zener mode, the negative TC indicates avalanche >> type .. > > > ** Both statements are wrong.
* So the Wiki is WRONG??
> > FFS learn to read. > > >> So...i pete the questions again. > > ** Who cares. > > > > ... Phil > >
"Robert Baer"
> Phil Allison wrote:
>> >> >>> The I-V curve indicates a zener mode, the negative TC indicates >>> avalanche type .. >> >> >> ** Both statements are wrong. > > * So the Wiki is WRONG??
** No, you are - fuckwit. FFS learn to read. ... Phil