Transistors Explained: Unipolar/Bipolar, PNP/NPN Keys, Differences & Uses for Beginners

Hello,
I am a beginner electronics and I started with the subject of transistors,
so I have some questions:
-What is the unipolar transistor for?
-What is the bipolar transistor for?
-What is the difference between a bipolar and unipolar transistor
-What is the difference between a PNP Key and an NPN Key
-What are the uses of transistors

I was looking for answers on Google, but as I mentioned, I'm a beginner
an electronics engineer and as I looked on the internet it is too "advanced language" for me

Google yourself a "beginner transistor"
http://elportal.pl/pdf/k01/25_18.pdf
http://elportal.pl/pdf/k01/26_13.pdf
http://elportal.pl/pdf/k01/27_13.pdf and subsequent parts.

Or read these pdfs.
https://sklep.avt.pl/webpage/praktyczny-kurs-elektroniki.html

Question 1 and 2
All transistors are important parts of more or less complex circuits (integrated and "unscaled") - they make for signal amplifying and signal controlling elements. However, please note that the transistor itself is only a transistor - only after attaching elements (resistors, capacitors, other transistors, etc.) can we talk about an amplifier.

Question 3
The most important difference between a bipolar and unipolar transistor is that the bipolar transistor is controlled current , i.e. the gain depends on the current strength based on the transistor, and the unipolar transistor is controlled voltage , i.e. the gain depends on the voltage at the gate. You can immediately indicate another difference - in the naming of electrodes (i.e. leads, do not confuse with our forum ). The bipolar transistor has base, collector and emitter while the unipolar transistor has respectively: goal, drain and source . There is also a difference in the construction and use in systems.

Question 4
The difference between the NPN and PNP key is that the NPN key is controlled by positive voltage on the base (relative to the emitter) and the current flows from the collector to the emitter, whereas in the case of the PNP key it is exactly the opposite: the current flows from the emitter to the collector and the key is controlled by a negative base voltage.

Question 5
Transistors are basically used everywhere - they are irreplaceable and it's hard to do something without them (at most the so-called "crystal radio"). Of course there are also electron tubes that used to "do" transistors, but today they are no longer used, with the exception of tube radios (in the event of an atomic war, read yourself), tube hi-end amplifiers and systems made by "tube fans" or amateurs who they make retro layouts from the last century.

Thank you very much for the comprehensive answer, but I have one more question:
How to control voltage and current.

It is not "voltage and current control", but voltage and current control, to do this you must know the basic laws and have basic knowledge. You have to read a lot about it and get to some things yourself, not just ask in the forum "how? What for? And why?" because you will still not understand.

Added after 3 [minutes]:

https://www.elektroda.pl/rtvforum/topic1726169.html
I recommend exploring and doing something of what they recommend there, you will certainly light up a lot of things, and if you do not know something, search first, then ask.

Describe in your own words what you mean by current and voltage control. The transistor can be operated, but not the voltage / current!

In my speech, the point was that in circuits based on bipolar transistors the signal gain depends on current flowing from the base to the emitter . However, in systems with unipolar transistors the gain depends on voltage between gate and source . Do you see the difference?

Since you are a beginner, for now take care only of bipolar transistors, when you master them then get yourself unipolar.

Each bipolar transistor has a parameter called hFE (or ? in other words - strengthening. If we lead to a situation (i.e. we build a suitable system) that 10mA will flow from the base to the emitter when hFE = 200, then the current flowing from the collector to the emitter is Ibe * hFE (base-emitter current * gain), i.e. in this case 2000mA, i.e. 2A. It is worth noting that not every transistor will withstand such current, and each transistor has a different hFE, but the average values are given in the catalog cards, which are taken in the calculations.

I know it can be gibberish for you so read something that colleagues said. I recommend the Electronics Course from myself at forbot.pl, everything is nicely explained there.

https://forbot.pl/blog/kurs-elektroniki-tranzystory-bipolarne-w-praktyce-id4315

and here the link from the beginning of the course:

https://forbot.pl/blog/kurs-elektroniki-napiecie-prad-opor-zasilanie-id3947

MiernikZKauflanda wrote:

In my speech, the point was that in circuits based on bipolar transistors the signal gain depends on current flowing from the base to the emitter . However, in systems with unipolar transistors the gain depends on tensions between the base and the emitter .Do you see the difference?

And since when do we have Base and Emitter in unipolar transistors ??

MiernikZKauflanda wrote:

2000mA or 1A

Interesting...

Sorry for stupid mistakes, I wrote at night, I have already corrected.

Thank you very much for the extensive answers, but the best explanation I found on YouTube, on the RS Electronics channel.
I understood that the transistor is used to turn on e.g. light bulbs, but not high voltage like 230V, only e.g. 1V,
so I already know what the transistor is for and I can close the topic