Go Down

Topic: What types of capacitors are these? (Read 3053 times) previous topic - next topic

Coding Badly


TonyWilk

I am generating random numbers (I built a dungeon dice roller using my circuit), but my ulterior motive is to produce damaged NP junctions, and then look at them with an electron microscope and microprobe. I'd like to see what tunneling damage looks like.
Interesting !

is that why you went for TO-18 (tin can) transistors then ?

Yours,
  TonyWilk

ChrisTenone

Interesting !

is that why you went for TO-18 (tin can) transistors then ?

Yours,
  TonyWilk

Yes, I figured the substrate would be easier to get at, but I've never opened one of those cans.

Well, that and they look cool and sciency. I put an oversized heat sink on the voltage regulator, just so the circuit would look badass.
What, I need to say something else too?

Grumpy_Mike

#18
Jan 24, 2018, 06:36 am Last Edit: Jan 24, 2018, 06:38 am by Grumpy_Mike
Quote
Tunneling as you know, is the process of an electron moving through an insulator without actually being in the insulator.
Not quite, it is electrons passing through a barrier that you not expect because that barrier is higher than the energy in the electron. Typically the barrier is caused by a PN junction in the silicon. Not really anything to do with insulators.

ChrisTenone

Not quite, it is electrons passing through a barrier that you not expect because that barrier is higher than the energy in the electron. Typically the barrier is caused by a PN junction in the silicon. Not really anything to do with insulators.
I guess I'm thinking of an electrochemical environment that does not have available conduction bands. That kind of insulator, not like a dielectric layer. I've learned a new engineering term here - barrier.
What, I need to say something else too?

Grumpy_Mike

Quote
I've learned a new engineering term here - barrier.
To be more specific this is a "potential barrier" to give it its Sunday name.

However there is nothing stopping a glass of water sitting on a table to suddenly appear on the underside of the table and fall to the ground. The physics are the same. This is possible but just very improbable due to the time you will have to wait for this to happen. A time greater than the total lifetimes of many universes. You just gotta love quantum mechanics. 

allanhurst

#21
Jan 25, 2018, 11:02 am Last Edit: Jan 25, 2018, 11:14 am by allanhurst
Note you're using a LM2924.

This is a very slow old dual opamp - GBW product only 1MHz.

I hope you're not expecting any gain at 1MHz...

There are much better devices around these days.


Allan

TonyWilk

This a very slow old dual opamp - GBW product only 1MHz.
OpAmp and Comparator actually

Yours,
  TonyWilk

MarkT

Yes, I have read that as well, and it fascinated me. Tunneling as you know, is the process of an electron moving through an insulator without actually being in the insulator. That is, it disappears from one location, and appears in another without occupying any space in between. Similar to how electrons move from one energy level to another in an atom, emitting a photon equivalent to the energy difference in the process.
No, that's not quite how I'd describe how the quantum world works - the electron has a definite non-zero
probablility to be in the insulator, the probability drops off exponentially with distance, but if the distance
is short enough there is a large enough probability it is at the other side of the insulator.  Electrons can't
occupy space anyway, they have, as far as we can measure, zero size.  Its the wave-function of the
electron that matters here, and that is defined over all of space and time, although becoming vanishingly
small at distance.

With the insulator although there is a probability the electron is in the insulator, its not a plausible place for
it to end up as it takes a lot of energy to move the electron from outside an insulator to inside it (this is
why it is insulating), and if the electron doesn't have that amount of energy it won't be observed to
end up in the insulator as a final state, so you could call that "dissappearing" and "reappearing" I suppose.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

ChrisTenone

Note you're using a LM2924.

This is a very slow old dual opamp - GBW product only 1MHz.

I hope you're not expecting any gain at 1MHz...

There are much better devices around these days.


Allan
OpAmp and Comparator actually

Yours,
  TonyWilk
Thanks Allan and Tony. I picked this chip because I use the comparator side to extract a square wave from the circuit's output, and the opamp side to conform the voltage to the microprocessor. That and I had 2 of them in a drawer.

Here's the output of the avalanche circuit that goes into the comparator:



The comparator feeds directly into the opamp, and here is the opamp output, which goes directly into a pin on the microprocessor:



So it works fine for my device, but I want to build a similar circuit together with a dual opamp, since I only had 2 of the LM2924s and they are not readily available. I've got LF353, LM358 and TLV2462 chips

But  perhaps I should stick with the vintage theme:
What, I need to say something else too?

ChrisTenone

Hi Grumpy Mike and Mark T. Thanks for your thoughts on quantum mechanics.

As a chemist, I've always used the "shut up and calculate" style to work with quantum mechanics. Working in a two year college for the last 30 years, has turned me into the quintessential sophomore, so my classical descriptions tend to be sloppy and throwaway.

Thank you Mike for the clarification. I'm more used to the 'potential energy barrier' as a thermodynamic quantity. A reaction requires a certain amount of "activation energy" in order to happen.  It's essentially the same thing, right?

I have an experiment where the students observe the spectrum of excited hydrogen gas*. They measure the wavelength of the visible lines and apply the Bohr model to derive the energy differences between the quantum states. Todays' students, as opposed to those 20-30 years ago, have no problem with an electron occupying discrete energy states. Since these kids are 'digital babys', that seems natural to them.

* about half of the students can see the 397 nm line. This is why I was amused by the other thread that discussed whether 395 nm was UV or visible.

I'm interested in your statement Mark, that electrons have no volume. I use electron diffraction, SEM and atomic force microscopy, all of which use electron volume (or at least cross-sectional area.) How should I reconcile those two concepts?
What, I need to say something else too?

TonyWilk

...and I had 2 of them in a drawer.
A chip in the hand is worth two in the distributor's stock.

... or something like that :)

Yours,
 TonyWilk

Grumpy_Mike

Quote
A reaction requires a certain amount of "activation energy" in order to happen.  It's essentially the same thing, right?
Sounds like it might be but I am no chemist. In fact I wanted to be one at the age of 11, but when I moved up to big school ( we do that at 11 in the UK ) the school had no chemistry lab, so I turned to Physics.

allanhurst

#28
Feb 06, 2018, 01:22 am Last Edit: Feb 06, 2018, 01:37 am by allanhurst
Quote
I'm interested in your statement Mark, that electrons have no volume. I use electron diffraction, SEM and atomic force microscopy, all of which use electron volume (or at least cross-sectional area.) How should I reconcile those two concepts?
Been a while since I did chemistry as a first degree.

I seem to remember that an electron in an atom or molecule was described not as a point, but  having a statistical probability of being in a particular part of space. Shrodinger, Dirac did the sums. . Not a point, but a sort of fuzzy shape  . Different orbitals have different shapes  - s, p, d etc and their combinations . Or the delocalised rings of benzene.   

Have things changed?

Allan


ChrisTenone

Schrödinger's description is still the basis for organic and much of inorganic chemistry. In an atom, you can't ever say where the electron is, just what the probability of finding it there is. The shapes are typically the 95% probable boundary. I went to school in the 1970s, and we haven't changed the basic concepts of atomic structure since then.
What, I need to say something else too?

Go Up