Testing the TK Tar Baby

[poynt99]

Once upon a time Ms. Gate and Mr. Source lived in a two dimensional world and were married, but eventually things didn't work out for them. Now in order to keep the peace, a certain minimum vertical distance must be maintained between the two of them. Let's call this distance "VGS". As long as the relative distance VGS is maintained and Ms. Gate is higher than Mr. Source, the two are content and life flows along normally.

From the diagram, we can see that Ms. Gate and Mr. Source live in the same plane, but are separated by distance VGS relative to each other. They each can move up or down as long as a minimum relative distance VGS is maintained between them and Ms. Gate is higher than Mr. Source. Both Ms. Gate and Mr. Source can live above ground level as shown in Fig. 1, Ms. Gate can be above ground level and Mr. Source below ground level as in Fig. 2, or both can be below ground level as in Fig. 3. In each of the 3 scenarios, Ms. Gate and Mr. Source are content because at all times a relative minimum distance VGS is maintained between them, and life happily flows along.

Moral of the story:

It doesn't matter where Ms. Gate and Mr. Source are in relation to ground level, as long as the relative vertical distance VGS is maintained between them and Ms. Gate is above Mr. Source, life happily flows along.

[TinselKoala]

That's a nice illustration, poynty. Golly, it sounds like you are saying that what is important is the _relative_ voltage between Ms Gate and Mr Source. Lol.


So then, if Ms Gate is nailed to the ground so that she can't float either up or down at all..... how then are the couple to keep that happy distance that keeps things flowing?

It looks to me like Mr Source will have to descend down below the ground level, to some negative height, to maintain that happy distance, if Ms Gate can't move because she's been chained to that bad old battery negative pole.


That's no problem, I'm sure they can manage that somehow, especially if Mr Source has a nice big pickle ...er ...shovel. But what if they don't always keep _exactly_ the right distance? I mean it's only a third or fourth part of the maximum distance they can be before they separate forever, but it has to be sufficiently apart enough for the space between them to let the little  "kiddies" run freely sideways between Mr Source and Uncle Drain.

What if the distance is a bit more than just enough, then a bit less than just enough, and so on? Would only a few of the kiddies get through to Uncle Drain, and then a lot of them, then only a few again?

Well, if Mr Source and Ms Gate are anything like mosfet structures, and the distance between them is anything like potential difference, AKA voltage.... then they will.

[Magluvin]

Well if Rose does not get this, then she must be just saying its wrong on purpose and she does realize the problem.

Its been said and said and said and described and described, again and again.

But Poynt brought it out in a way that everyone should understand what is happening. ;]

Mags

[MileHigh]

Four Ms. Gates tied down to the ground helpless and squirming.

Four Mr. Sources grovelling below in the basement looking up in fear.

Four Mz. Drains looking down at the helpless squirming Ms. Gates with their high-potential electron injection guns at the ready.

Sounds like an idea for a movie!  lol

[TinselKoala]

Her conception of the way mosfets work is flawed. And since it is impossible for her to acknowledge that her conception is wrong, she blocks her own understanding of the issues.

In the following quote, from her reply to .99's scenario of marital bliss, she writes:

The ONLY way that current can pass in a clockwise direction - wherever its source - through any PART of the Q2 is IF there's an appropriate signal applied to the Gate.  Without any signal the switch is open.  With a negative signal the switch will REPEL a positive current flow.  Only with a positive signal will that clockwise current flow be able to bridge the gate to run from the drain rail of the circuit to the source rail of the circuit.  All of which is very easy to prove.  Just disconnect Q2's Gate leg from the circuit and see what happens.  One would get an ENTIRE CESSATION OF ANY CURRENT AT ALL.

The ONLY way: This part betrays her lack of conception that AC will "flow" through the gate capacitance whether the mosfet is on or not. She has not watched or understood my video showing a capacitor of the same value as her gates, passing a 1.5 MHz AC signal and lighting up a bulb with practically no attenuation.... no mosfet "switch" involved at all, JUST THE MOSFET's INPUT CAPACITANCE.

Without any signal: Here she betrays her lack of understanding that it is not "signal" that the gate works by, but CHARGE. The gate will stay "open" to whatever degree it is CHARGED, and the charge will stay on the gate if it is not REMOVED actively or allowed to FLOW AWAY passively. If the mosfet is simply disconnected at the gate, then whatever charge is on the gate will keep the mosfet's drain-source channel conducting until that charge leaks away. She has not watched or understood my video showing the effect of CHARGE on a mosfet gate and what happens if you don't drain it away.

With a negative signal: This is simply wrong. A "negative signal" to a mosfet gate doesn't repel, or cause the mosfet to repel, anything, it simply drains away the CHARGE that keeps the drain-source channel flowing, faster. It is the CHARGE on the gate that opens or closes the gate by its electric field acting across the gate's dielectric, and if there is a negative electrical charge here in an n-channel mosfet, yes, the gate is "closed" by a repulsive field. This has nothing to do with the mosfet itself "repelling" anything, any more than a garden hose's closed valve "repels" anything if you close it even tighter.
Designers frequently apply AC to a mosfet gate for exactly this reason-- see my TinselKoil 2.0 for an example of this strategy applied to mosfets to turn them off rapidly. It has NOTHING WHATEVER to do with a mosfet "repelling" anything. Her concept of the functioning of a mosfet is severely flawed. Unfortunately I do not have a video, other than my sstc videos, that address this point directly... it is so fundamental that NOBODY who knows anything about mosfets, or who can READ, could possibly make the mistake she makes here.

bridge the gate: Nothing "bridges the gate" in a functioning mosfet except electric charge. Electric charge is the mechanism for AC passing the gate to the drain/source channel, as illustrated in my "capacitors" video; DC cannot pass from the gate to the other pins; there is normally no current except the superimposed AC "bridging the gate" and that current will flow whether the gate is open or not. She here betrays confusion about the physical model of a mosfet. What we call the "GATE" is really more like the screen-door spring, and it is the mosfet's drain-source channel that is really the "gate" that restricts flow of current.
Examining the sketch of the mosfet's guts in the Mims page I posted would clear up the matter... if only she could see it or would look at it.
We apply a charge to the "screendoor spring". This opens the screendoor more or less to let the little flies representing electrons get from the outhouse (the drain or positive rail) to the kitchen (the source or negative rail.) The charge on the screendoor spring is different from and does not participate in the flow of flies from the outhouse to the kitchen.
And every one of my videos which includes a mosfet illustrates this simple fact.

drain rail: Grit my teeth again. Misuse of jargon has always been a peeve of mine. Hang ten, source rail... whatever. We know what you are talking about, even if you don't, Ainslie.
The circuit's "rails" refer to the power supply and its delivered voltages. There is a positive rail that is connected to the positive supply source, and there is a negative rail that is connected to the ground or negative pole of the supply or both. These represent the extremes of voltage that the supply can provide to the circuit, and since many circuits are laid out LIKE I ILLUSTRATE IN MY RECENT VIDEOS EXPLAINING THIS, they sort of even look like railway rails, and all the circuit's action happens "between" the rails, as I illustrate.
There is no such thing as a drain "rail" or source "rail" although the latter might be considered the negative rail if the circuit is wired that way.

easy to prove: Yes, it is. Unfortunately what Ainslie offers as "proof" is neither proof, nor correct. Again.... She clearly has not watched nor understood my video, Mosfets: how do they work 2, where I show exactly what happens when a mosfet's gate is DISCONNECTED ENTIRELY, and it refutes her "proof" and might surprise even Ainslie, if she only had the wit to understand it and if her understanding wasn't blocked by what she "THINKS" she understands already.

(ETA: SWITCH. Here again and continually, she betrays her lack of understanding of linear conductance in a mosfet. It's not always a "switch" like a relay is, Ainslie. It's more like a valve, which is normally operated fully open or fully closed, but which can VERY EASILY be operated like a smoothly regulating faucet valve, fully controllable and consistent from fully off to fully on and anything in between, depending on the MAGNITUDE OF THE GATE CHARGE, or, put another way, on the distance between Mr Source and Ms Gate interpreted as a difference in _relative_ potential... a voltage.)