Calm down, this your personal view on this topic. It is not useful to cry Ohm's Law isn't so we must question everything just because resistors have a temperature coefficient.
We try, folks forget that all the collector current flows through the base to get to the emitter the base current is the part that's lost. Super beta transistors have VERY thin bases, etc.
The part that interests me isn't an issue of noise so much as one of integer quantization of signal, which to my limited understanding is independent of DC currents (but sensitive to Beta). If your point is that this *must always* be well dithered by the associated shot noise, then I'll let it go and start finding something else to compulse about.
Thanks very much for your help with this,
Chris
That would be a good assessment of the situation, I can't see an important place where this would not be the case.
Dr. Hawksford's original paper regarding quantum effects was mostly a THOUGHT EXPERIMENT, based on what is possible.
What amazes me is how few here seem to know that there is a DEEPER LEVEL of performance that is usually not taught to electronics engineers, because there is just not enough time in class to do so.
For example, jfets. Many here think that they know and understand jfets, especially their noise characteristics. They might have looked through a textbook like 'Low Noise Electronic Design' by Moschenbacher and Fitchen and think (like I once did) that they pretty much know everything about low noise design.
However, look at a book like: 'Noise in Electronic Devices and Systems' by M.J. Buckingham, and be prepared to have 'your socks knocked off'!
1/f noise, who really has a handle on it? Any of you? What about over a temperature range? Part geometry? Processing?
I first found this book in 1984, and even sent a copy to Dr. Vandenhul, at his request. (He and I find this sort of thing, fascinating). You might too, but I am sure it will open some eyes to how virtually everything is really deep physics that we just sort of use the best that we can to make something practical.
What amazes me is how few here seem to know that there is a DEEPER LEVEL of performance that is usually not taught to electronics engineers, because there is just not enough time in class to do so.
For example, jfets. Many here think that they know and understand jfets, especially their noise characteristics. They might have looked through a textbook like 'Low Noise Electronic Design' by Moschenbacher and Fitchen and think (like I once did) that they pretty much know everything about low noise design.
However, look at a book like: 'Noise in Electronic Devices and Systems' by M.J. Buckingham, and be prepared to have 'your socks knocked off'!
1/f noise, who really has a handle on it? Any of you? What about over a temperature range? Part geometry? Processing?
I first found this book in 1984, and even sent a copy to Dr. Vandenhul, at his request. (He and I find this sort of thing, fascinating). You might too, but I am sure it will open some eyes to how virtually everything is really deep physics that we just sort of use the best that we can to make something practical.
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just my 2 cents regarding john´s frequency unrelated "blips" in the spectrum of a ahard driven TL741, could it be "shot noise" or "popcorn noise" wich is behind his findings?
Effects of circuitbreakers, fuses and such are propable do to current dependend, current modulated contact resistances. Contact materials have only a limited range of suitabilitie and should be choosen accordingly.
For example, I once needed a relay able to switch a low level dc signal (nA to mA range) with no contact-resistance variations what so ever. The best I could find was by the manufacturer specified for 20uA to 100mA if I remember correctly. I could
only find relays with somehow reliable and consistent contact resistance when working in a rather limited current range and voltage range. Both factors influence contact resistance and usability depends on the application. The usual low pessure contacts offcourse are especially troublesome.
Effects of circuitbreakers, fuses and such are propable do to current dependend, current modulated contact resistances. Contact materials have only a limited range of suitabilitie and should be choosen accordingly.
For example, I once needed a relay able to switch a low level dc signal (nA to mA range) with no contact-resistance variations what so ever. The best I could find was by the manufacturer specified for 20uA to 100mA if I remember correctly. I could
only find relays with somehow reliable and consistent contact resistance when working in a rather limited current range and voltage range. Both factors influence contact resistance and usability depends on the application. The usual low pessure contacts offcourse are especially troublesome.
Or, may be it would work the same way, because I learned physics of semiconductors from people from Tomsk Institute of Semiconductor Devices, who used to design them?
Edit: speaking of relay contacts... 2 days ago died a guy who I knew from Russian DIY Audio forum. Last Saturday he decided to melt some silver from relay contacts. Got sick, called ambulance, they diagnosed fever and left... 2 days after ha was hospitalized with pneumonia... Relay contacts contain Cadmium, vapor of cadmium oxide is very dangerous.
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In silvered ceramic and mica caps that are used with dc polarization silver-migration is an issue. This sometimes manifests itself by exploding of caps in high power applications. Detoriation is only a qestion of fieldstrength and time
John, speculation, sure, what else could it be until proven rigth or wrong? what you call impossible is not impossible at all despite the fact that I could not proof it, but you could easely exclude this possibilitie by repeating the experiment. As to "impossible amplitude",
are we talking about ancient j-fet stuff wich was known of sometimes huge random noise shots or not?
are we talking about ancient j-fet stuff wich was known of sometimes huge random noise shots or not?
Ummm...
Sorry, I thought this was the BlowTorch preamp discussion. I seem to have wandered into the Electronics Philosophy Thread...
Sorry, I thought this was the BlowTorch preamp discussion. I seem to have wandered into the Electronics Philosophy Thread...
Useability is also a function of the app circuit. If you need a relay to switch gain and the best one you find has 10 milliohm contact variation, and you need at least -100dB distortion, make sure the series R you're switches is several kohms.
A good design uses parts that are not perfect (none are of course) in such a way that it doesn't compromise the final product.
jan
The main effect of charge quantisation, when it occurs, is noise: either shot noise or partition noise (which are almost the same thing anyway). It depends on current, because the likely fluctuation varies like the square root of current. Signal quantisation, when it occurs, would be so small as to be negligible when compared with noise because the charge on the electron is so small.Chris Hornbeck said:
Let's do a ballpark estimate. Assume a circuit node has a capacitance of 10pF. If it is isolated from other parts of the circuit then adding an electron will change the voltage by 16nV. What is the smallest audio signal you are likely to get at a relatively high impedance (i.e. isolated) point? Perhaps 5mV from an MM. The quantisation is 110dB below the signal. However, nothing in an audio circuit is isolated, as otherwise you don't have a circuit. An electron can be, in effect, halfway onto a node but still halfway off the previous node. The quantisation does not occur. Even in a valve, the electrons approaching an element affect the potential of the element before they arrive.
Would you see this quantisation anywhere? Yes, possibly. You need a combination of low capacitance and low signal level. Capacitor microphone? Although there the charge stays constant and the capacitance varies so maybe not.
Note that what matters is not the capacitance of, say, the base of a transistor but the capacitance of that entire circuit node. My guess is that if this was a problem it would be seen in integrated circuits, as they have tiny circuit nodes with very low capacitance.
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