2N2222 Zener noise

Started by Bitrex November 26, 2010
I suppose I could set things up to do the research myself, but since I'm 
feeling lazy I thought I'd check first: By how much do you have to 
reverse bias the emitter-base junction of a common transistor such as 
the 2N2222 before it starts getting appreciably noisy? Does it have to 
be above the 5-6 volt breakdown voltage, or will significant noise occur 
before that point? I'm looking for a noise source that will work with a 
3 volt supply.  Maybe a different transistor with a lower breakdown voltage?
On Nov 26, 9:26=A0am, Bitrex <bit...@de.lete.earthlink.net> wrote:
> I suppose I could set things up to do the research myself, but since I'm > feeling lazy I thought I'd check first: By how much do you have to > reverse bias the emitter-base junction of a common transistor such as > the 2N2222 before it starts getting appreciably noisy? Does it have to > be above the 5-6 volt breakdown voltage, or will significant noise occur > before that point? I'm looking for a noise source that will work with a > 3 volt supply. =A0Maybe a different transistor with a lower breakdown vol=
tage? You are snookered by the physics. Reverse-biased diodes break down by two different mechanisms depending on the voltage applied acorss the junction, the Zenner (quantum tunneling) mechanism at alow voltages - less than 5V - and the avalanche (impact ionisation) mechanism at higher voltages. http://ecee.colorado.edu/~bart/book/book/chapter4/ch4_5.htm Avalanche breakdown gives a noisier leakage current than quantum tunnelling - with avalanche breakdown there is always the chance that an electron will make it all the way across the gap without generating a second electron-hole pair, killing the leakage current until a cosmic ray or a radioative atom in the vicinity generates a new charge carrier pair to restart the avalanche process. Quantum mechanical tunnelling is also a random process, but it is a single random process, without the second stage of avalanche multipication to generate lots of outliers. With a 3V supply rail you are stuck with Zener breakdown. You may have to settle for a pseudo-random binary sequence generator, or amplifying the Johnson noise from a resistor - 1nV per root hertz for a 50R resistor at room temerature, rising as the square root of the resistance, bearing in mind that "low noise" integrated circuit op amps typically also generate 1nV per root hertz white noise at room temperature. -- Bill Sloman, Nijmegen
On 11/26/2010 6:26 AM, Bill Sloman wrote:
> On Nov 26, 9:26 am, Bitrex<bit...@de.lete.earthlink.net> wrote: >> I suppose I could set things up to do the research myself, but since I'm >> feeling lazy I thought I'd check first: By how much do you have to >> reverse bias the emitter-base junction of a common transistor such as >> the 2N2222 before it starts getting appreciably noisy? Does it have to >> be above the 5-6 volt breakdown voltage, or will significant noise occur >> before that point? I'm looking for a noise source that will work with a >> 3 volt supply. Maybe a different transistor with a lower breakdown voltage? > > You are snookered by the physics. Reverse-biased diodes break down by > two different mechanisms depending on the voltage applied acorss the > junction, the Zenner (quantum tunneling) mechanism at alow voltages - > less than 5V - and the avalanche (impact ionisation) mechanism at > higher voltages. > > http://ecee.colorado.edu/~bart/book/book/chapter4/ch4_5.htm > > Avalanche breakdown gives a noisier leakage current than quantum > tunnelling - with avalanche breakdown there is always the chance that > an electron will make it all the way across the gap without generating > a second electron-hole pair, killing the leakage current until a > cosmic ray or a radioative atom in the vicinity generates a new charge > carrier pair to restart the avalanche process. Quantum mechanical > tunnelling is also a random process, but it is a single random > process, without the second stage of avalanche multipication to > generate lots of outliers. > > With a 3V supply rail you are stuck with Zener breakdown. You may have > to settle for a pseudo-random binary sequence generator, or amplifying > the Johnson noise from a resistor - 1nV per root hertz for a 50R > resistor at room temerature, rising as the square root of the > resistance, bearing in mind that "low noise" integrated circuit op > amps typically also generate 1nV per root hertz white noise at room > temperature. > > -- > Bill Sloman, Nijmegen >
Thanks for your reply and for the enlightenment regarding the difference between breakdown mechanisms. Instead of trying to amplify Johnson noise, perhaps I can use a spare opamp section of the project as a hysteretic oscillator and make a charge pump to kick the voltage up above the 5 volt threshold? I wonder if a low voltage op amp like the LM324 acting as a charge pump would be able to get the voltage high enough to initiate the avalanche breakdown mode - I'm not sure what the '324's output can swing at such low voltages, but I bet getting 5 volts with a 3 volt supply with such a circuit might be pushing it.
Bill Sloman wrote:
> On Nov 26, 9:26 am, Bitrex <bit...@de.lete.earthlink.net> wrote: > >>I suppose I could set things up to do the research myself, but since I'm >>feeling lazy I thought I'd check first: By how much do you have to >>reverse bias the emitter-base junction of a common transistor such as >>the 2N2222 before it starts getting appreciably noisy? Does it have to >>be above the 5-6 volt breakdown voltage, or will significant noise occur >>before that point? I'm looking for a noise source that will work with a >>3 volt supply. Maybe a different transistor with a lower breakdown voltage? > > > You are snookered by the physics. Reverse-biased diodes break down by > two different mechanisms depending on the voltage applied acorss the > junction, the Zenner (quantum tunneling) mechanism at alow voltages - > less than 5V - and the avalanche (impact ionisation) mechanism at > higher voltages. > > http://ecee.colorado.edu/~bart/book/book/chapter4/ch4_5.htm > > Avalanche breakdown gives a noisier leakage current than quantum > tunnelling - with avalanche breakdown there is always the chance that > an electron will make it all the way across the gap without generating > a second electron-hole pair, killing the leakage current until a > cosmic ray or a radioative atom in the vicinity generates a new charge > carrier pair to restart the avalanche process. Quantum mechanical > tunnelling is also a random process, but it is a single random > process, without the second stage of avalanche multipication to > generate lots of outliers. > > With a 3V supply rail you are stuck with Zener breakdown. You may have > to settle for a pseudo-random binary sequence generator, or amplifying > the Johnson noise from a resistor - 1nV per root hertz for a 50R > resistor at room temerature, rising as the square root of the > resistance, bearing in mind that "low noise" integrated circuit op > amps typically also generate 1nV per root hertz white noise at room > temperature. > > -- > Bill Sloman, Nijmegen >
Oh really, I've also been led to believe and educated, years ago, that zener mode and impact mode is a balance at 5 volts and anything under that goes into "impact" mode and above is zener. Looking at the behavior of the commonly known 5.1 Vref diode where a diode is in series with the zener stabilizes the effects between the two. I think you may want to do a better job of memorizing that document you red before posting your proclaimed expertise drivel. If it were me, I would've suggested to look at a "NOISE DIODE" and not throw a crap load of physics that you most likely barely understand. Things like SHot and Johnson Noise could also be a good help as references to loop up.. Now, I've seen some tricks done using a tunnel diodes in my day.. Jamie.
Bill Sloman wrote:
> On Nov 26, 9:26 am, Bitrex <bit...@de.lete.earthlink.net> wrote:
[...]
> With a 3V supply rail you are stuck with Zener breakdown. You may have > to settle for a pseudo-random binary sequence generator, or amplifying > the Johnson noise from a resistor - 1nV per root hertz for a 50R > resistor at room temerature, rising as the square root of the > resistance, bearing in mind that "low noise" integrated circuit op > amps typically also generate 1nV per root hertz white noise at room > temperature. >
Dudes, dudes ... what is so difficult about making a higher voltage from 3V? -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
On Fri, 26 Nov 2010 03:26:21 -0500, Bitrex
<bitrex@de.lete.earthlink.net> wrote:

>I suppose I could set things up to do the research myself, but since I'm >feeling lazy I thought I'd check first: By how much do you have to >reverse bias the emitter-base junction of a common transistor such as >the 2N2222 before it starts getting appreciably noisy? Does it have to >be above the 5-6 volt breakdown voltage, or will significant noise occur >before that point? I'm looking for a noise source that will work with a >3 volt supply. Maybe a different transistor with a lower breakdown voltage?
You win't find a transistor that zeners at 3 volts. Well, maybe an exotic microwave one. Do you need high-quality, flat, Gaussian noise? How about doing it digitally, with a pseudo-random shift register? John
On Nov 26, 2:30=A0pm, Jamie
<jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:
> Bill Sloman wrote: > > On Nov 26, 9:26 am, Bitrex <bit...@de.lete.earthlink.net> wrote: > > >>I suppose I could set things up to do the research myself, but since I'=
m
> >>feeling lazy I thought I'd check first: By how much do you have to > >>reverse bias the emitter-base junction of a common transistor such as > >>the 2N2222 before it starts getting appreciably noisy? Does it have to > >>be above the 5-6 volt breakdown voltage, or will significant noise occu=
r
> >>before that point? I'm looking for a noise source that will work with a > >>3 volt supply. =A0Maybe a different transistor with a lower breakdown v=
oltage?
> > > You are snookered by the physics. Reverse-biased diodes break down by > > two different mechanisms depending on the voltage applied acorss the > > junction, the Zenner (quantum tunneling) mechanism at alow voltages - > > less than =A05V - and the avalanche (impact ionisation) mechanism at > > higher voltages. > > >http://ecee.colorado.edu/~bart/book/book/chapter4/ch4_5.htm > > > Avalanche breakdown gives a noisier leakage current than quantum > > tunnelling - with avalanche breakdown there is always the chance that > > an electron will make it all the way across the gap without generating > > a second electron-hole pair, killing the leakage current until a > > cosmic ray or a radioative atom in the vicinity generates a new charge > > carrier pair to restart the avalanche process. Quantum mechanical > > tunnelling is also a random process, but it is a single random > > process, without the second stage of avalanche multipication to > > generate lots of outliers. > > > With a 3V supply rail you are stuck with Zener breakdown. You may have > > to settle for a pseudo-random binary sequence generator, or amplifying > > the Johnson noise from a resistor - 1nV per root hertz for a 50R > > resistor at room temerature, rising as the square root of the > > resistance, bearing in mind that "low noise" integrated circuit op > > amps typically also generate 1nV per root hertz white noise at room > > temperature. > > Oh really, I've also been led to believe and educated, years ago, that > zener mode and impact mode is a balance at 5 volts and anything under > that goes into "impact" mode and above is zener.
Then you had better go and get yourself a better education.
> Looking at the behavior of the commonly known 5.1 Vref diode where a diod=
e is in series with > the zener stabilizes the effects between the two. You would be thinking of the 1N821 through 1N829 6.2V voltage reference diodes, which did include a a forward diode to compensate for the temperature coefficient of a 5.6V "zener" diode. http://www.datasheetcatalog.org/datasheet/motorola/1N823.pdf http://206.209.106.106/datasheets/Zeners/AppNotes.pdf The breakdown voltage you get with a pure zener (quantum tunnelling) mechanism decreases with increasing temperature, while an avalanche breakdown voltage increases with increasing temperature. At 5.6V the balance between the two mechanisms favours the avalanche route enough that the voltage across the reverse biassed diode increases by the same 2mV/K that the voltage across the forward diode decreases. http://en.wikipedia.org/wiki/Zener_diode
> =A0 I think you may want to do a better job of memorizing that document > you red before posting your proclaimed expertise drivel.
Since you managed to confuse the the 5.1V "zener" diode, which has a roughly zero temperature coefficient, with the 6.2V reference diodes which do include a forward diode, your own advice can be seen as less than reliable.
> =A0 =A0If it were me, I would've suggested to look at a "NOISE DIODE" and=
not
> =A0 throw a crap load of physics that you most likely barely understand.
Google doesn't throw up much on noise diodes. The nearest thing to something useful came from here http://www.electronicspoint.com/noise-diode-t23382.html
> Things like Shot and Johnson Noise could also be a good help as > references to look up..
I did refer to Johnson noise. Google on that and you get to http://en.wikipedia.org/wiki/Johnson%E2%80%93Nyquist_noise which does include a reference to shot noise. http://en.wikipedia.org/wiki/Shot_noise Neither is going to be of much help to the OP, who wants a solution to a problem - not the education that you obviously failed to absorb.
> =A0 =A0Now, I've seen some tricks done using a tunnel diodes in my day..
The real trick with tunnel diodes today is finding where you can buy one. The difficulty with tunnel diodes is that they are broadband devices. If you don't mount them in a properly designed transmission line environment, they will oscillate at a frequency your oscilliscope can't follow, and the voltage levels that you will see - at frequencies that your oscilliscope can follow - won't look anything like what you wanted and expected. -- Bill Sloman, Nijmegen
In article <pI2dndTgUJPm8nLRnZ2dnUVZ_rCdnZ2d@earthlink.com>,
 Bitrex <bitrex@de.lete.earthlink.net> wrote:

> I suppose I could set things up to do the research myself, but since I'm > feeling lazy I thought I'd check first: By how much do you have to > reverse bias the emitter-base junction of a common transistor such as > the 2N2222 before it starts getting appreciably noisy? Does it have to > be above the 5-6 volt breakdown voltage, or will significant noise occur > before that point? I'm looking for a noise source that will work with a > 3 volt supply. Maybe a different transistor with a lower breakdown voltage?
Are MOVs noisy? Luxeon Rebel LEDs flicker in the 2V/microamp range, which I'm hoping is their MOV rather than defects in the chip slowly burning away. -- I will not see posts or email from Google because I must filter them as spam
John Larkin wrote:
> On Fri, 26 Nov 2010 03:26:21 -0500, Bitrex > <bitrex@de.lete.earthlink.net> wrote: > >> I suppose I could set things up to do the research myself, but since I'm >> feeling lazy I thought I'd check first: By how much do you have to >> reverse bias the emitter-base junction of a common transistor such as >> the 2N2222 before it starts getting appreciably noisy? Does it have to >> be above the 5-6 volt breakdown voltage, or will significant noise occur >> before that point? I'm looking for a noise source that will work with a >> 3 volt supply. Maybe a different transistor with a lower breakdown voltage? > > You win't find a transistor that zeners at 3 volts. Well, maybe an > exotic microwave one. > > Do you need high-quality, flat, Gaussian noise?
What on earth is flat Gaussian noise? A flat, ie. even distribution is not a Gaussian, so perhaps I'm misunderstanding this statement. Please enlighten... BTW, the new Agilent 3352x arb. generators have a nice feature that lets you adjust the bandwidth of the noise, which is Gaussian. They also have a LFSR noise generator, but it's not analog but rather on/off. I guess if it were to be analog, it would have to let you select some number of bits to gather for each output. This would give a flat analog noise. It would have been nice if you could select the distribution of the noise. Perhaps I'll send these ideas on to Agilent. They have been very nice to me over the years, taking many of my ideas directly to the scope and generator prod. devel. managers. It can also use the noise to modulate a PWM signal, so coupled with a little flyback pulse generator, can be used to simulate a lot of jittery physical phenomena, like laser pulses. -- _____________________ Mr.CRC crobcBOGUS@REMOVETHISsbcglobal.net SuSE 10.3 Linux 2.6.22.17
"Bitrex" <bitrex@de.lete.earthlink.net> wrote in message 
news:XcCdnet8IpWVNHLRnZ2dnUVZ_rOdnZ2d@earthlink.com...
> On 11/26/2010 6:26 AM, Bill Sloman wrote: >> On Nov 26, 9:26 am, Bitrex<bit...@de.lete.earthlink.net> wrote: >>> I suppose I could set things up to do the research myself, but since I'm >>> feeling lazy I thought I'd check first: By how much do you have to >>> reverse bias the emitter-base junction of a common transistor such as >>> the 2N2222 before it starts getting appreciably noisy? Does it have to >>> be above the 5-6 volt breakdown voltage, or will significant noise occur >>> before that point? I'm looking for a noise source that will work with a >>> 3 volt supply. Maybe a different transistor with a lower breakdown >>> voltage? >> >> You are snookered by the physics. Reverse-biased diodes break down by >> two different mechanisms depending on the voltage applied acorss the >> junction, the Zenner (quantum tunneling) mechanism at alow voltages - >> less than 5V - and the avalanche (impact ionisation) mechanism at >> higher voltages. >> >> http://ecee.colorado.edu/~bart/book/book/chapter4/ch4_5.htm >> >> Avalanche breakdown gives a noisier leakage current than quantum >> tunnelling - with avalanche breakdown there is always the chance that >> an electron will make it all the way across the gap without generating >> a second electron-hole pair, killing the leakage current until a >> cosmic ray or a radioative atom in the vicinity generates a new charge >> carrier pair to restart the avalanche process. Quantum mechanical >> tunnelling is also a random process, but it is a single random >> process, without the second stage of avalanche multipication to >> generate lots of outliers. >> >> With a 3V supply rail you are stuck with Zener breakdown. You may have >> to settle for a pseudo-random binary sequence generator, or amplifying >> the Johnson noise from a resistor - 1nV per root hertz for a 50R >> resistor at room temerature, rising as the square root of the >> resistance, bearing in mind that "low noise" integrated circuit op >> amps typically also generate 1nV per root hertz white noise at room >> temperature. >> >> -- >> Bill Sloman, Nijmegen >> > > Thanks for your reply and for the enlightenment regarding the difference > between breakdown mechanisms. Instead of trying to amplify Johnson noise, > perhaps I can use a spare opamp section of the project as a hysteretic > oscillator and make a charge pump to kick the voltage up above the 5 volt > threshold? I wonder if a low voltage op amp like the LM324 acting as a > charge pump would be able to get the voltage high enough to initiate the > avalanche breakdown mode - I'm not sure what the '324's output can swing > at such low voltages, but I bet getting 5 volts with a 3 volt supply with > such a circuit might be pushing it. >
It'd probably be easier to get a single transistor blocking oscillator to work, the charge pump gives just under Vccx2, if you need more you have to cascade doubler stages. For a one-off you could liberate the erase oscillator from a scrap cassette deck - the inductor is usually styled like an IFT, so nice neat finished job.