Logic Gate at Physical Level: hows it work?

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no one knows?

I've googled my ass off over this one.

I don't even know what you are talking about, lol...

logic gate:

An integrated circuit or other device whose inputs and
outputs represent Boolean or binary values as voltages
(TTL uses 0V for False or 0, +5V for True or 1). Different
gates implement different Boolean functions: AND, OR,
NAND, NOR (these may take two or more inputs) NOT (one
input), XOR (two inputs). NOT, NAND and NOR are often
constructed from single transistors and the other gates made
from combinations of these basic ones. These functions are
all combinatorial logic functions, i.e. their outputs depend
only on their inputs and there is no internal state. Gates
with state, such as latches and flip-flops, are
constructed by feeding some of their outputs back to their
inputs.

I just want to know how it works :-)

maybe it was invented by aliens

Try a technical hardware forum. Perhaps they will know a little more?

Ummm... a lot of it is basically transistors, but at the physical level... I'd have to dig around in my bookmarks that I haven't reinstalled yet... IIRC there's an IBM tech doc in there about gate design, with an emphasis on current leakage reduction.

it really depends on your medium. Digital lines are much different from analong lines. For the most part it depends on voltage. Analog lines have a baseline (and depending on what type of modulation you are using), for instance in some instances the binary operands of on or off are simply denoted by lower or higher voltage. For digital it is mostly based on change, and becomes a function of voltage over time. This is basically a function of on or off, but that is not to say that on means 1 and off means 0. If that were the case, it would be impossible to determine the difference between a 0 bit, and the end of a transmission. Instead, (depending on what type of modulation you are using) for instance, when the signal is started, a 5V pulse for x nanoseconds would denote a binary 1. If, after x ns the signal did NOT change, that would denote that the next bit is also a 1. If it DOES change, that would denote a 0. There are different types of modulation, and each one has a different way of determining on or off.

Look up analog and digital modulation, and I'm sure you can find a good explanation.

There are all sorts of different ones, so there is no way I can describe them all here (or remember how they all work). For instance, Phase-shift Keying, Frequency-shift keying - which is broken down in to sub categories: minimum shift keying; Gaussian minimum shift keying, and very minimum shift keying; Amplitude-shift keying; Continuous Phase Modulation, Pulse modulation, etc. (those are all the ones I remember from my data communications class - If I had my notes I would copy and paste em for you.)

At least I think thats what you were asking.