How does a transistor work?

Question

Electronics

I'm considering a bipolar transistor for now.
1) A transistor in electronics is primarily an amplifier.
And in computers it is a kind of key.
So, how does one device contain two such wonderful properties?
2) I just can’t find the principle of operation of a transistor in a computer. This is seen as a key that outputs 0 or 1. But this key is not mechanical, so it can change state many times in a short period of time.
I searched all over: "transistor key", "transistor as a key or switch", etc.
There was no description of his work anywhere.
There are some schemes like this
one. But we see that the key is also mechanical, that is, it must be closed, opened by oneself.
It doesn't fit as you can see.
My only thought is that with a low voltage at the base, the electrons cannot pass through the depletion layer, there is no current in the external circuit - this is 0, when the voltage at the base is strong enough, the electrons calmly pass through this layer, respectively, the current through the external circuit also starts go is 1
I don’t know if it’s a right or wrong thought ?!

Answer 1

1. Computers mainly use field-effect transistors.
2. The transistor allows you to control a larger current with the help of a small current.
3. To understand how it works, you need to read about the various modes of operation of a bipolar transistor. At the top you've been left with links already.
In your picture, the key and Bat1 can be replaced by any rectangular signal. Then there will be no mechanical key.

Answer 2

So, how does one device contain two such wonderful properties?

Depending on the mode of operation. If the transistor stage operates with only two very different collector current values, then this can be considered a key (digital) mode. But at the same time there is still gain - a low-power input signal drives more power at the output.
If the collector current can take on any value from a certain allowable range, then this is an amplifying mode.

I don't know if it's true or not?

If you are going to study solid state physics and design transistors themselves, then no.
And if you develop circuits on transistors, then this is not at all the question that should be asked. In 95% of cases, it is enough to consider a bipolar transistor as a current amplifier. The remaining 5% will be covered by relevant literature and a set of practical experience.

Answer 3

How a transistor switch works
Transistor-transistor logic

Answer 4

https://m.habr.com/ru/post/133136/
as for amplification and frequent switching - it means that a weak control current (signal from the microcontroller leg) can control a large current (powering another chip). And since the microcontroller can jerk its leg thousands of times per second, a transistor, including such a rapidly pulsating current, can be created.

Answer 5

Everything is clear and understandable here
https://www.youtube.com/watch?v=MUBvPNVf1rI
etriz.ru/Chapters/003.html
https://meanders.ru/transistors.shtml
well, of course, you need to take into account the characteristics of the transistor itself, the maximum collector emitter voltage, collector base, and cutoff frequency