"Ok, thanks Tim, that gives me a bit more understanding of the issue. But what is the process used to control the current sent to the gate on the memory? In a memory transistor you change the current at the gate to allow (or prevent) a connection between the source and the drain, right? "
No, a _voltage_ (proportional to a charge, through Q = CV) is applied to a gate. This then opens up a conductive path below the gate, in the silicon below. The rest follows from Ohm's Law.
Don't think in terms of "current sent to the gate." Think in terms of voltage on the gate. (Though there are currents flowing, as I noted above with Q = CV and V = IR and so on.)
"Maybe a few switches can control the switching of hundreds or even thousands of these gates, but I would think the gates, being dependent on the logic or control switches for their own switching could not switch faster then the logic or control switches. If the control switches have a similar source, gate, and drain setup, then something would need to control the current to their gate. If the highest level control switches do use a design like that then what control's the current change on their gates. I can't imagine it would be a physical switch because it would be too slow (and probably too big even if you only need a very few circuits at this level), but I can't understand how a transistor that operates based on currents being applied at a gate could switch without something external to it controlling the switching."
I'm not sure what you mean with all of this above. Rather than try to understand your understanding of the terms, I'll refer you to the articles and books.
Understand that small voltages or currents can control large current flows (and hence voltages elsewhere). This is the essence of electronics: the ability to switch currents off and on, the ability to _amplify_ voltage and current. Same thing that happens with vacuum tubes, where the plate voltage manipulates current flows.
You need to understand just the most basic of all things: a mere few hundred thousand electrons (a charge) on a gate in a MOSFET can open that conducting channel I mentioned and let _amps_ of current flow.
This was known about in 1935, actually, before the Bell Labs transistor discovery. The Field Effect Transistor (FET) works as I described. The physics of depletion layers is actually very easy to get an intuitive understanding of. The Metal-Oxide-Semiconductor (or Silicon) structure is called MOS and the device is thus a MOSFET.
Small controlling voltages (or currents, in bipolar-type devices) can control large current flows. This is why they are called "gates." Open the gate and the resistance drops. Ohm's Law takes care of the rest.
This is how amplifiers work--the solid-state amplifiers in every piece of audio or video gear. Like vacuum tubes, or "valves," another metaphor."
"It might be that to really understand it I need to develop a solid basic understanding of the whole subject. Either actually taking, or doing independent reading equivalent to a "Electrical engineering 101" class and a "Basics of integrated circuits" class, but while I am interested in the answer, I'm not sure I want to put that much time in to researching it."
Taking a night school class in this stuff is an utter waste of time, unless you plan to go further. The operation of a MOSFET will likely be zoomed past in about 5 minutes. And prepared students will likely have already read about it. (I admit that many students never bother to do reading in advance of their classes.)
I was reading articles on these things when I was in high school, even building circuits with tunnel (Esaki) diodes. Understanding what MOS is, what FETs are, how a simple dynamic memory cell works, is easy. Draw some pictures, understand what is physically happening, do some more reading, draw some more pictures.
No special classes are needed. I keep referring to "Scientific American." I will repeat: go dig up some articles at your nearest library. Understanding how these gems of technology work is much more psychically rewarding and useful in this forum than most things are.
--Tim May |
