Transistors: Practical Designations, Parameters & Replacement Examples - Understanding BC547

Hello!
I have a question; Well, from the beginning of my fascination with electronics, when assembling the circuits, when the transistor came into use - the same problem always appears: the total confusion in the mind: after a series of transistors read and stuck to the head, I understand everything, but in practice every time when it's time to turn on the transistor into the system I do not know how to do it. Maybe I'm stupid, but I think I read with understanding, even more: I understand, but in practice after this series of information I have a lot of confusion in my head and I have no idea at last what parameters mainly pay attention to different systems, the same with replacements, on a simple example of transistor BC547 (I purchased various AVT kits, including 160 transistors in housings to-92 by 10p)
And nowhere can I find information if any of those I have is suitable for use in the system (whatever).
For this purpose, I dare to ask for some data about the transistors that I have (for a few days I order a package, including various transistors) - well, but that's not the point - I would like to learn how to use and select / change transistors in practice (I know that there are catalogs with replacements), unfortunately, I did not find one that I would have.

Maybe the easiest way is if I give the transistors I have in stock.
I would ask for some hints I will not read on pages filtered by the slogans "transistor - replacements, transistors in practice" etc ...
So I would ask if someone has an idea to give the first better scheme using one of these transistors:

Maybe it will illuminate you:
http://forbot.pl/blog/artykuly/elektronika/kurs-elektroniki-7-tranzystory-w-praktyce-id4315

Unfortunately, I already know all this by heart, it is just one of the articles I have explored several times.
I have the impression that I need a simple scheme using some simple elements (eg NE555, some capacitor / s etc.) to start using transistors correctly in practice - and I know that these are quite unique and worth knowing due to a lot of applications as simple solutions.
With transfer it seems to me it's so easy ..
Unfortunately, it is quite different in practice (so far on the contact plate)
Maybe even someone tells me if any of the above transistors is suitable as a replacement for BC546 / 7/8, which is so often seen on various diagrams in the network, i.e., for example, on the Electrod straight led flashing with voltage + 12V applied:

https://www.elektroda.pl/rtvforum/topic996119.html

In my opinion, you should approach the problem the opposite, that is, to start with, choose a few simple schemes to implement. You prepare a list of elements, including transistors, you assemble and then ew (based on the catalog notes) you try to use a replacement in a particular application . If you do not know what a transistor can be replaced on a schematic, then ask on the forum, it will be a specific point problem, it is easier to solve such a thing. As always, the practice leads to the so-called general knowledge, when the experience tells you what replacements in the system you can use.

2n3904 / 06 pnp is so popular "for everything", even for HF
Here are some simple layouts:
https://www.google.pl/search?q=2n3904+led+str...kIKA&biw=1280&bih=667#tbm=isch&q=2n3904+led+&* & imgrc = ZaPlkEfFSSiP3M:

2N3904 is NPN transistor, not PNP.

Exactly. In addition, this stage can give half a bag of well-known element models, but it probably is not about enumeration. Nothing can replace the practice, there is a whole "drive" and stimulus in it.

2N3904 / 06 pnp or 2n3906 pnp as equivalent to 2N3904 npn. I thought it was obvious.

No - this is not obvious, especially since you then give the link to 2N3904.

Especially for beginners, reliable data is worth giving. Such a man is imprisoned erroneously and then it will be difficult to eradicate.

Thank you very much for the answers. Everything over time - just like other elements
As for the storage I have different kits, led dups, SMD diagonals, resistors, transistors, photoresistors, phototransistors, photodiodes, capacitors - most from the smallest to the highest possible value (parameters)
As of today, I spent more than 1000 zlotys on everything (including multimeter, soldering irons, power supplies, modules, stabilizers, but from what I see, it is confirmed by every electronics hobbyist or professional: there is still something missing

Returning to the topic; in the end I do not know, gentlemen, can you replace the transistor I replaced with BC547 in the system? The structure is finally pnp or npn, because I have a little confusion, which is true.

Thank you very much for the answers, if someone dropped some relatively simple diagrams using one of the transistors that I have at the present moment?
I liked my approach very much - it's true - with every element until I burned a few LEDs or resistors (although it is the simplest one that can be), I did not understand 100% "how and with what it is" at my place This is alternating - the easiest way - first a lot of theory, then simple examples in practice, return to theory and everything goes together.
Best wishes!

2N3904 npn BC547
2N3906 pnp BC557
It is worth entering in the google type of the transistor and checking the order of the pins from the housing.
In the case of 2N3904 and BC547 it is different!

You can check alternatives here:

https://www.elektroda.pl/rtvforum/zamienniki.html

possibly by entering in the phrase phrase eg "BC547 replacement", or internationally "BC547 replacement". Of course, you must approach the results of such searches with "head", comparing the parameters (especially those important from the point of view of our project) in the directory notes.

And with time, the appetite grows, then the person starts to wonder how to count the different systems, from the connections of the resistors to, for example, calculations of the transistor's operating point. There are old good books on the secondary market, eg "Radioamator's Guide", where the authors present this knowledge in a fairly legible way, not only theoretical, but also the most tangible and practical.

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Returning to the topic; in the end I do not know, gentlemen, can you replace the transistor I replaced with BC547 in the system? The structure is finally pnp or npn, because I have a little confusion, which is true.

Nobody will tell you, you have chosen a nasty "system" that can work or not even for transistors from one production series, uses the transistor's unusual property, negative dynamic resistance when broken in the reverse direction.
And by the way, transistors "tested" in this system are subject to degradation of parameters such as beta or noise parameters.

Your list of transistors are models that are mostly not popular in Europe, 2Nxxxx is American, Cxxx or Axxx are Japanese transistors, actually they are 2SCxxx 2SAxxx, abbreviated names were written on the casing,
so the C945 is 2SC945 but it would not be that simple there are also transistors simply named C945 and such a datasheet exists.

When I started, I gained elements from various sources that hit (wyłuty, remains from liquidated plants, etc.), I made a list of basic parameters, not to look in DS just to have everything in one place at hand.
The most important parameters for transistors are:
Type, conductivity (NPN / PNP), maximum collector voltage Vce0, maximum collector current Ic, maximum power Pd loss, current gain Hfe, maximum frequency ft
Catalogs of replacements do not include anything more, and often take even less to compare.
The transistors you have would divide into several groups:
1. general purpose low voltage power 20-60V currents 100-200mA as 2N3904
2. with increased collector current> 500mA as S8050
3. high voltage> 100V as MPSA42
4th in, part > 400MHz as S9018

It is also worth noting which the manufacturer has marked as complementary pairs, eg 2SA733 and 2SC945

Generally, there is nothing to expect miracles in the TO92 casing, even if the transistor has a 1.5A catalog like the S8050 housing and the associated poor cooling conditions limit the possibility of using it as a medium power transistor (like BD135)

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And nowhere can I find information if any of those I have is suitable for use in the system (whatever).

Matching transistors and substitutes is a task for the layout designer, only he knows the exact requirements to be met, someone who can not design, will never be sure that he chose well, even if he used a catalog of substitutes.
In the diagrams in the websites, there were elements marked that they are not allowed to be changed into other ones of even the same parameters.

There are a lot of circuits where at first glance you can say that the selection of the transistor will not be critical, as long as it meets the basic requirements for Vce0 and Ic.
The vast majority of systems (well-designed) do not work at the limit of the transistor's capabilities, so the chances of successful conversion are greater.

In your collections there are no unusual elements, for example, for example, 2SD965 transistor for pulse operation with high currents is very difficult to replace - used in self-expanding generators, or MPSA18 single transistor with beta of about 1000.

Thanks a lot. A big plus for you.
Could you recommend the "more popular" transistors, hm. Until now I was convinced that it is the most popular housing and I did not even know that it affects its work and parameters. Big thanks for correcting.
Maybe you could recommend some kit with transistors or recommend what to buy (I am going to buy the next missing items and I am making a list), I would like to order a dozen different transistors of 5-10pcs) because they do not hide, simplify many systems and are really grateful elements.
I am admiring my way. I looked through datasheets and various replacement catalogs for BC546 / 7 and found a lot but nothing I could use in the system.
As for switching on: the transistor is said to be best suited - as it is described in the various circuit breaker schemes.
What solution would you recommend?
Maybe another solution without this transistor / Ew. Different?
I am open to any ideas and thank you for your answers.
It helped me a lot
greetings

Usually, the choice of transistor is not as critical as you think, the transistor is quite a universal element and in 95% of circuits using low power transistors you can insert an element that differs significantly in terms of parameters

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Could you recommend the "more popular" transistors, hm. Until now I was convinced that it is the most popular housing and I did not even know that it affects its work and parameters.

TO-92 is indeed a very popular case for low-power transistors, its main limitation is the power loss limited to 300mW (do not take it too literally when in datasheets write more).
I am writing this because the most common reason for using a different transistor than the TO-92 or SOT-23 casing is the need for higher currents and / or power losses.

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Maybe you could recommend some kit with transistors or recommend what to buy (I am going to buy the next missing items and I am making a list), I would like to order a dozen different transistors of 5-10pcs) because they do not hide, simplify many systems and are really grateful elements.

What you have useful in many systems, make a list of basic parameters, know what you have, the ability to use the transistor is not closely related to the type you will be able to build a 2N39xx layout and convert it to BC5xx will not cause you a problem.
As I was a beginner, I was building circuits on what was on hand, including the use of the transistor Ge instead of Si, although it is already an inflection and after such a change can be problems.

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I am admiring my way. I looked through datasheets and various replacement catalogs for BC546 / 7 and found a lot but nothing I could use in the system.

What layout? Are you still having an avalanche system? if so, better forget in 99.99% of the actual applications of this system you will not meet. There are diacs from that, and if it has transistors, yes
link
Asking about the layout with the avalanche puncture you will not get the answer you expect, it's like you asked the carpenter what pliers to buy for nailing - no nails are hammering.
If you are interested in this system, look below
link

When you are looking for substitutes for something that is very popular, you have little chance of finding someone who has the same "problem",

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As for switching on: the transistor is said to be best suited - as it is described in the various circuit breaker schemes.

Everyone is suitable, but not for every load, otherwise they say how you know what kind of current and voltage you want to control, the transistor will be found.

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What solution would you recommend?

Focus on what you want to build.
Building circuits with discrete transistors is currently less popular than before, so you need to better apply for searching.
First, review this:
link
link
link
I used to search a lot on the internet and found many books and websites with transistor layouts, but I can not show you everything at once.

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Maybe another solution without this transistor / Ew. Different?

If you find it difficult to find a chip without BC5xx it means that it is a very popular transistor that is worth having.

A huge thank you to everyone, especially I am grateful to the author of the post above, I am currently reading links that you have given and generally like me, um ... "Blown away"
I gave up this arrangement, which does not mean that I will drill through this system Fact - I am very interested in this application. Until now, he will browse the links.

Thank you very much!
PS: I made the first circuit on the 2Nxx transistor

Subject to be closed.

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I gave up this arrangement, which does not mean that I will drill through this system Fact - I am very interested in this application.

In that case, you will also be interested in:
noise generator based on avalanche puncture link
Or using the transistor as a Zener diode
link - Figure 8
Either using an avalanche transistor to green nanosecond pulses
link
With such a generator and oscilloscope you can do TDR.

In each of the above cases, avalanche penetration leads to slow (and sometimes even rapid) degradation of parameters, so the transistor once used in these systems should be treated with disabilities, unsuitable for other applications.
First, you should master the basic properties and uses of the transistor before you take on these unusual and little-known.

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Until now, he will browse the links.

If you are only going to browse it, download it, for a beginner to be heavy, but you can look at the diagrams you can, in order to have an orientation in what systems the transistor can work and what are the ways to turn on the transistor into the system
link

below the circuits on the oscilloscope, simple circuits, as it seems to you that you understand the operation of the transistor is to analyze the operation of these circuits (you will know what else you need to learn)
link

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Subject to be closed.

As soon? I just started