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Old 16th March 2012, 07:49 PM   #31
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Hey Popilin,
What is your discovery? The circuit you presented is nothing special. Just what you could expect from ECC82. Itīs not very linear, especially when you say it could be used at very high levels.
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Old 16th March 2012, 09:26 PM   #32
popilin is offline popilin  Argentina
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Hi DF96
How can an electron to know if it was created by thermionic effect or by photoelectric effect?
In a photodiode NOT all electrons emited arrives to anode, after all the electron cloud/space charge isn't my invention, it exists before I was born.
I worked with Vka in te order of 4V !!!
I cosidered "secondary emission"(Anode emission), and covered the anode with black tape.
I made an anode bombardement with a LASER beam !!!
The cathode area was >> than anode area, and "secondary emission" influence was in the orther
Delta(h) = 10^-38 J s
Then I consider photon-electron interactions, same order
Delta(h) = 10^-38 J s
I cosidered everything and the electron cloud was the guilty.
How do you measure emission? I can't, I only can measure the total current.
If you think that in a photodiode all the electrons emitted ends up at the anode, It seems to me that you are confusing emission with total current.

Last edited by popilin; 16th March 2012 at 09:41 PM.
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Old 16th March 2012, 09:32 PM   #33
popilin is offline popilin  Argentina
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Hi revintage
Read posts #28 and #29.
It seems to me that you dont read anithing and you don't know what's the idea, read post #24.
Regards
Johann

Last edited by popilin; 16th March 2012 at 09:37 PM.
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Old 16th March 2012, 10:47 PM   #34
DF96 is offline DF96  England
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With a low anode-cathode voltage (4V) a small bit of space charge will reduce current. No surprise there. Space charge reduces current in a normal valve too - that is what it is supposed to do. Photodiode operation roughly corresponds to temperature-limited thermionic valves: most, if not all, emitted electrons will go to the anode. Anode current will not vary much with anode voltage, but will vary greatly with light/heat. Once you have a substantial space charge developed (high light/heat) then current varies slowly with light/heat but quickly with anode voltage (3/2 power law).

Triode linearity does not depend on trying to do away with the 3/2 law, but ensuring that the anode and grid law are the same - then you get constant mu and low distortion. You are trying to reduce the very effect which makes valves work properly!
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Old 16th March 2012, 11:53 PM   #35
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Hey Johann,

Whatever your ideas are, again: The circuit you presented is nothing special. Just what you could expect from ECC82. Itīs not very linear, especially when you say it could be used at very high levels.
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Old 18th March 2012, 04:29 PM   #36
popilin is offline popilin  Argentina
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Hi DF96
You still haven't understood Planck constant experiment, BTW the accepted value for Planck constant is
h = 6.626... x 10^-34 J s
Very close to the result obtained with less electron cloud/space charge !!!

I will try another approach
Lets a vacuum diode at zero total current i=0 now the thermionic effect dominates, we have only electron cloud/space charge and the current density j can be derived from Fermi-Dirac distribution, and is given by
equation (1) (Doesn't matter it's form)
For a given current density j (In the limit of large current densities) the total current i>o
Maxwell Equations=>Poisson Equation=>Child-Langmuir Law or 3/2 power law
equation (2)
For a transition from eq.(1) to eq.(2) we need increase the current. (increasing Vak par exemple)
As current increases, the electrons of the cloud are accelerated and go to the anode.
Not all electrons can escape from the cloud, increasing Vak more electrons can do it and the electron cloud effect tends to decrease as current increases.
From a given Vak, Ia vs Va graph tends to a straight-line.The 3/2 power law tends to a linear law.
Now, if we add a grid, we have a triode, and the analysis is more complex, however, for Vgk=0 the analysis done is a good approximation, and it can be extrapolated to a triode, even at Vg<0.
We must note that electron cloud/space charge ever exists, without it we haven't a valve anymore.

I hope I have explained the reason that most of us used the linear region to design a valve circuit.
Analysis is simple and crude, but can illustrate the point.
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Old 18th March 2012, 04:39 PM   #37
DF96 is offline DF96  England
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You still don't get it do you? If you deliberately run a valve in the region where the space charge is small then you are approaching the temperature-limited region. In this region the triode is not linear: it stops being a triode because the current depends on cathode temperature rather than electrode voltages. This is how a thermionic noise diode works.

Please go away and read up how triode valves really work. There is plenty of good stuff on the internet. I have tried to correct your misunderstanding but there is a limit to how much free tuition I can give to an obstinate student. Maybe someone else can take over. I have had enough.
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Old 18th March 2012, 06:43 PM   #38
popilin is offline popilin  Argentina
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Master.
Sorry for the examples.6BQ5 is a pentode, but in triode connection also serves.
Are you saying that the dissipation limit curve is outside the linear zone??????
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Old 18th March 2012, 06:48 PM   #39
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Quote:
Originally Posted by popilin View Post
Yes, electron cloud effect, that's one reason for tetrode and pentode invention.
The electrons between cathode and anode disturb the pass of new electrons.
Charges with same sign tend to repel each other.
I had seen that many times in the lab, didn't you made Thermionic Effect experiment, or measure the Planck constant?
Wasn't this the reason for g3 in a pentode and beam plates in a tetrode? Or ios this another effect?
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Old 18th March 2012, 07:00 PM   #40
popilin is offline popilin  Argentina
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Hi razorrick1293
I read that in my childhood, in a RCA handbook, but Master DF96 says I'm wrong, I didn't understand anything, neither triodes, neither datasheets.
Best regards
Johann

Last edited by popilin; 18th March 2012 at 07:18 PM.
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