A Totally Worthless - But Interesting - Circuit

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R

RogerFoote

Guest
Good one Wayne!

The really ambitious could do this on a bag of 100 devices to show behavioral differences!

Roger
 
Be aware that zenering the b-e junction degrades the device noise and beta (perhaps other parameters too). This is why you see anti-zener clamp diodes across that junction in the front end of low noise preamps.

Indeed interesting and pretty much worthless.

JR
 
I think this was just mentioned in another thread (?). Or maybe I just saw it where Wayne did.

Unexpected low-level photon production can create a number of problems. The JPL folks found a odd excess of pixel leakage corrents in the vicinity of the output amplifier on a CCD image sensor, which turned out to be light emission from that amplifier. It showed up on long exposures and required that the chip be cooled to see the effect. I think the cooling also increased the light emission. They wound up powering the amplifier down until they wanted a readout.
 
[quote author="JohnRoberts"]Be aware that zenering the b-e junction degrades the device noise and beta (perhaps other parameters too). This is why you see anti-zener clamp diodes across that junction in the front end of low noise preamps.
JR[/quote]

Pease suggests discarding the device after the experiment for this reason.
 
Yup, just splainin why... and connecting dots...

Talking about light, I recall working with some prototype Phillips BBDs back in the early '70s that were in open or glass topped packages. The room lights were adding noise and generally corrupting the audio signals as they passed through the shift registers. Took us a while to figure that one out. :?: I think we ended up putting black tape over the devices.

Some IC packaging material is slightly radioactive and this was a problem with early high density memory chips.

Noise comes in many flavors.

JR
 
It's not totally worthless.
The "Pease effect" has some value according to this fellow.
See:
http://tinyurl.com/2wdxhr

ZAP
 
[quote author="RogerFoote"][quote author="bcarso"][quote author="JohnRoberts"]Be aware that zenering the b-e junction degrades the device noise and beta (perhaps other parameters too). This is why you see anti-zener clamp diodes across that junction in the front end of low noise preamps.
JR[/quote]

Pease suggests discarding the device after the experiment for this reason.[/quote]

Well, if someone does try it on 100 devices, you didn't hear it from Roger when the EPA comes 'a knockin![/quote]

Or you could repackage them as zeners. Bob Moog and many others used to use transistors in this way, as I recall.
 
[quote author="mediatechnology"].

Next time I break a CFL lamp I'll have the hazmat crew take the transistor.[/quote]

..reminds me off the hazmat crew in "Monsters Inc" - clipping the hair off the
poor guy who got contaminated with a childs "sock" :green:
 
[quote author="bcarso"]
Or you could repackage them as zeners. Bob Moog and many others used to use transistors in this way, as I recall.[/quote]

http://www.uni-bonn.de/~uzs159/noise.html

Lot of synths (maybe most of them) used similar noise sources.

OTOH (and on topic), does anyone have any idea how (and if) EsubN of "zenered"
transistor changes over (long period of) time.

cheerz
urosh
 
Do you mean the noise spectral density of the breakdown mode, or the e sub n of the transistor when it has been subjected to reverse breakdown for a period of time?

As I recall the change is not so much in e sub n for normal bias as it is in beta. As far as the constancy of noise as a breakdown diode I have no idea.
 
[quote author="bcarso"]Do you mean the noise spectral density of the breakdown mode, or the e sub n of the transistor when it has been subjected to reverse breakdown for a period of time?
[/quote]

Noise in breakdown mode.
 
Another way to get a small voltage (or current)
http://tinyurl.com/2bbr44
the output is completely isolated.

ZAP
 
[quote author="mediatechnology"]
I took Bob's advice and will be throwing this transistor away after I've had my fun with it.

OK, where's Wavebourne to also point out what's already been said.

Thanks Brad for reading the entire post. :thumb:[/quote]

I am back Wayne after a beautiful week on a Diamond Peak near lake Tahoe!

Now, what is DVM? Sounds like DMV (associated with DUI)

(Forgive me my ignorance!) :green:

I though it is a kind of noise measuring device, no?
 
[quote author="bitman"]Digital Volt Meter

[/quote]

Thanks!

It is definitely better than DUI! :grin:
 
[quote author="mediatechnology"]
I though it is a kind of noise measuring device, no?

Look at the polarity at the input of the "DMV." (sic)

Where's that negative voltage coming from? No, I wasn't "DUI" when I drew that.

It's a voltage generator. Zenering the B-E junction makes photons and a photo diode out of the C-E junction. (At least we're led to believe.)

Glad you had a nice trip!

I hadn't been in the shop since posting this and there was that little tortured 2N3904 with the clip leads still connected. I gave it a good funeral. :cry:[/quote]

What happened to it? Why funeral? What did you measure after torturing it? I used cb junctions for diodes, be junctions for Zeners developing hybrid ICs, but did not have a clue if breaking down a be junction causes any damage. At least, after measuring of breakdown voltages on a curve tracer transistors were still usable, especially well selected and matched ones!

It may be also a Hall or Peltier effect. If cooling a body helps to increase a voltage it may be a Peltier effect: collector has less thermal resistance with the body than emitter has.

I totally forgot physics of semiconductors that I knew excellent long time ago... Potential barriers... Energetic dips... Yes, generation of photons is possible, and it is possible that photons add some energy to electrons causing a negative potential on collector.

I like this idea, it is excellent, if opamps on the same crystal are identical! If not, at least input currents will be smaller!

http://electronicdesign.com/Files/29/6362/Figure_02.gif

But... One LED and couple of photo diodes will do the same trick. Even 3 identical LEDs will work well. I think of something similar to power electret mics from 48V phantom source (I want to build a phased mic array from cheap capsules).
 
[quote author="Wavebourn"]

What happened to it? Why funeral? What did you measure after torturing it? I used cb junctions for diodes, be junctions for Zeners developing hybrid ICs, but did not have a clue if breaking down a be junction causes any damage. At least, after measuring of breakdown voltages on a curve tracer transistors were still usable, especially well selected and matched ones!
[/quote]

Reportedly allowing be junctions to reverse zener degrades beta (hfe) and noise performance, which is why clamp diodes are routinely used in low noise designs across be junctions to prevent transient reverse avalanche from power supply cycling or cap coupled signal transients.

I read about this in Motchenbacher and Fitchen's "Low Noise Electronic Design" decades ago. I took their word for it..

JR
 
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