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Does a capacitor charges smooth, or in stairs?
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StillTrying:

--- Quote from: Labrat101 on June 08, 2020, 07:40:03 am ---I said I was "NOT KNOCKING"
--- End quote ---

I know you weren't, I was saying you could if you want, I wouldn't mind, it might lead to me making an easy minor improvement that I've missed.

Assuming there's was a long thin plate capacitor, I don't see the problem in it being a just a capacitor at very low speeds, and just a transmission line at very high speeds, the problem would be in the middle were it's it a bit of both.

Nominal Animal:
Something in all this reminded me of a funny thing when dealing with heat flow (as opposed to equilibrium).  You get similar impedance mismatches that affect how and where the heat is transmitted; it too behaves in many ways as a wave.  Feels very unintuitive that you can change how heat flows from hot to cold by just slipping in a very thin sheet of material with a different heat transfer characteristic, but that's what happens in real life... impedance mismatch, really.
It's too easy to forget that a lot of thermodynamics applies to equilibrium states, and the dynamics are much more complicated and interesting.

Same here.  I can imagine a circuit board having a semicircular disc shaped trace when dealing with a high frequency signal where the staircase is undesirable and a smoother behaviour wanted; the trace then acts sorta like a spectrum spreader – not a filter because it does not dampen any frequencies, it just retards some of the wave so that the arrival of the wavefront is spread out in time.

I'm beginning to think that even if this does not matter for many/most practical circuits, as an educational approach to ensure the students grasp how different models are needed to describe the important features depending on the situation/context, this is superior.
GlennSprigg:
Wow...  I chose to not read beyond the 1st few replies...  :)

Let's talk the most simple basics...
Capacitors charge/discharge continuously/smoothly on an 'ascentotic curve'...
which never actually peaks!!  I don't care how long it has been charging, or what
'curve' you draw, it is ALWAYS still charging, but by lesser & lesser & lesser amounts.
There are no 'STEPS'. Just a continuous analog reductive progression. But there's a problem.

Consider a ball thrown perfectly vertical, which eventually comes down again. OK...
Did it ever STOP at the top??  NO!!  It passed ZERO 'speed' for ZERO time!!So it never stopped.
I know where I'm going here mathematically... but do you ??
Labrat101:
Ok I got something.

I change some or the resistor to try and get a better results.
The Cap is 10nf @ 1.6kv  the resistor is 1k ohm . 
I tried 100ohm it worked but as using lower voltage was hard to get a clear picture.
the pulse Gen is set @ 2Mhz .. 9volt .. 100ns
The resistor is in parallel with the cap.
I did not show the pulse as a second channel as the probe was loading the circuit .
The Sharp peek is the pulse .
I used the analogue as it has a faster response .
Is this the staircase or is it something else   :popcorn:  or dodgy cap  ...

DannyTheGhost:
This reminded me about one thing I was studying in earlier university courses.
In mid 80s scientists started developing SETs - single-electron transistors.
They were creating thin films of Au, typically, above some dielectric thin film on metallic substrate, but they stop the process before Au creates uniformal coating, so there is islands of Au clusters, typically ~10nm. That gives it around tens of aF (attoFarads) of capacitance, which in turn, started creating Coulomb Blockage effect. Then they were using scanning tunnel microscope (STM) and its tip acting like electrode. Coulomb blockade occurs by 'charging' cluster with STM tip and tunneling effect, and because of really low volume of Au cluster when it charges by a 'single' electron tunneling effect stops and there is no current. And, of course, it creates steps in voltage needed to charge or discharge this cluster.
In this extreme example 'capacitor' indeed charges in steps  :D 
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