BC547 and BC557 Transistor Replacement in TO-220 package?

[bd139]

Depends. Which is the problem. Thr bd139 device spread is immense both on fT which isn’t even listed on the data sheet and the dc beta is very wide. At 100khz I’ve had to hand select specimens before.

BC547 is literally 1/10th to 1/20th of the cost and is a much better small signal transistor. I don’t understand why anyone would use bd139 here.

Obviously not sure if the application space here but the usual constraints aren’t audio but 2MHz-ish, the limit of most of the commercial function generators out there.

Bd139 is my favourite transistor hence the username and I know how to use them up to RF but for small signal they are shit.

[Adam60]

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I really hope this is picked up but my fear is this teacher does not have much knowledge about transistors and is just following a text book with some schematics / examples / tests.
I mean, how hard is it to find some BJT's to do some tests for students, or to look up some prices?

First off, I want to thank all of the people who took a moment to offer their thoughts on this subject without any snarky remarks. The fact that so many chimed in tells me that we all have different viewpoints on just about any given subject, and that there are many solutions to my post. I will take them all to heart and after some consideration, I will make a decision that is best for my class.
To broaden this out a bit, I am a College Professor and I teach automotive apprentices. Although I may not be as brilliant as some on here, I do know my way around motive power electrical and electronics fairly well and although I am not an electronics engineer, I do alright for my profession. As for my class, they are not here to learn all about the electronics world and we give them some fairly simple projects to build just to see how some of these components work and come together. Oddly enough, I can even explain the operation to them without the help of a textbook. I can read a schematic and build circuits all by myself.
Doctorandus, I am not sure what I did to provoke your condescending remarks, but in the future if you have something negative to say, maybe keep it to yourself. I was enjoying reading your post until I came to that and I really see no need for it. It is a beginners forum and if you think you are that smart, go to the advanced forums and post away. Thanks again everyone for your help.

[IconicPCB]

That is DoctorANDus... not DoctorANus..
EDIT:.. now that he has corrected spelling...this comment seems to be without context...bugger

[Ian.M]

.... except if he's being one.   

This forum is more civil than most, but sometimes some of us step over the line and need to be called out.   I've done it my self, been called out and apologised for it. 

If that was an intentional misspelling, I must congratulate Adam60 on a delightfully subtle twist to a flaming! 

@Adam60: Please bookmark the topic so you can update us with your decision and how it works out with your class.

[Adam60]

My apologies for the mis-spelling. I have gone in and corrected it and want to say that I do not need to stoop to that level to get my point across.

As I said earlier, the students are automotive technicians and I will probably just buy bags of these transistors for cheap wherever I can find them. I always have a conversation with my classes about working with tiny parts like this and they seem to understand. The problem is that several teachers with less understanding of the subject matter who teach out of books and use schematics they are unsure of, also use these same pieces. The more they get used, the more they are bound to break. Always looking for solutions to make life smoother for everyone. All we can do Cheers.

[Ian.M]

So get bags of a dirt-cheap 'jellybean' near equivalents to the ones in the book. and explain to your class they are an acceptable substitute and why.  The teachers who can only teach straight from the book will prefer the parts with the 'right' part number, leaving your class with transistors that are a lot less mangled!   

It also helps teach an extremely valuable lesson in choosing acceptable substitute parts.  You can also take the opportunity to explain that one does *NOT* make unauthorised substitutions in safety critical applications.

[Doctorandus_P]

Doctorandus, I am not sure what I did to provoke your condescending remarks, but in the future if you have something negative to say, maybe keep it to yourself. I was enjoying reading your post until I came to that and I really see no need for it. It is a beginners forum and if you think you are that smart, go to the advanced forums and post away. Thanks again everyone for your help.

First: Tnx. for the background information.
It was never my intention to be condescending, and at the moment of writing I had no idea that my remark would be explained in a negative way, If I had realised that I would not have said it in the first place. I know it's somehow my fault, and not yours, but If I refrain from saying (typing) anything that *could* be explaind in a negative way it would result in not ever saying anything to anyone anymore.
I've got (vague) lists in my head of things not to say. A classical example of this is that I've learned to not call people "stupid" (Just meant as an example, not calling you that). In my dictionary "stupid" simply means "having a (significantly?) below average IQ". And I do not see this as something bad, but just as a simple statiscical fact. By definition 50% of all people have a below average IQ. As far as I know there is no correlation between IQ and happiness. If any, it's probably the other way around. If "stupid" people ask a question on a forum, they get some answers, which gives them some Idea's and they're happy / content with it. If I ask a question on a forum it is seldom that I get a response that I had not thought of already myself, and different responses only add to the confusion to the point that I simply stopped asking questions myself. (Being "smart" and seeing a gazillion things, but not being able to sort through them or assign priorities is not easy. Nobody can help, because everybody is "stupid". Not being able to connect because there is a gap of a few sigma's. (This is not a good recipy for happyness, but I'll stop here out of fear of rambling on in a 100 page essay)).
As a passtime I try to help random strangers by answering questions and giving them idea's they probably had not thought of themself. Part of that is trying to make an estimation on what sort of answer would be fitting. Too simple an answer and it's useless, too complex an answer and it does not get understood and also ignored.

Just before typing this post I edited my previous post and removed the text under the cut line.
I hope you are willing to re-read that post without discarding everything because of the last unfortunate remark, for which I appoligse again.

[Adam60]

Apology accepted and post remains intact. I do want to say this though. One of the hardest things when you become a teacher is to learn how to dial it down so your audience understands what you are saying. It is not that they are "stupid", it is just that they are not at that same level. There are many levels of learning and just telling someone something only hits on one of them. The fact that they do not get it does not make them stupid, it just means they don't comprehend what you are trying to say. I believe Doctorandus that you are probably at the expert level in your chosen profession and the rest of us are not. Years ago I may have made the same remarks about people in general. Age has taught me to be a better teacher. I thank you for your comments and all others. Good food for thought.

[3roomlab]

how about this horse ?
2SC6144 NPN / 2SA2222 PNP in TO220F

[jobitjoseph1]

I am also struggling with the same problem, which solution did you find? can you please share?

I have a very old PCB in volume that has to-220 slot I need an equivalent of BC557 in TO-220. Or any part number that matches the specifications of bc557 transistor given in this features section
https://components101.com/transistors/bc557-transistor-pinout-datasheet

I am also ok with using an adapter board if such thing is easily available. Any thoughts?

[Vovk_Z]

Does anyone know what transistor in a TO-220 package would substitute for a BC547 and BC557?
I have students knocking legs off these like crazy and would like to substitute with something a little beefier. Thoughts?

TO-92 and TO-220 are too far from each other, so there can't be a real substitution. But there can be something similar in a much closer TO-126 case. For example TO-126 649/669, or TTA004/TTC004.

[Yansi]

I don't understand the strange problems of the people here are trying to solve.  Why one needs to replace TO92 by TO220.

Just stick yo damn TO92 into the holes of the TO220, if you put on the PCB a wrong footprint.

If pinout does not match and you need BCE instead of CBE (or EBC, depending which side you read the TO92 from), look into BC639/640, or for example 2SC945/2SA733 or whatever.

[Jwillis]

You could make transistor module boards with PCB pin boards and Dupont pin headers. Heck with it, make them create transistor module boards. Teaches soldering, responsibility and respect for their own creations.

[rsjsouza]

This thread is indeed quite strange. Although I hate waste, I am also practical.

The prior pricing shared in this thread is outdated (inflation and all), but you can still get 1000 transistors for around US$60 or 4000 transistors for US$120. Hardly a problem, especially considering you might get much cheaper at non-official distributors...

https://www.mouser.com/c/?q=bc557

[Zero999]

As above: they're cheap enough to consider them to be consumable.
https://www.digikey.co.uk/en/products/detail/diotec-semiconductor/BC547B/13164496

EDIT: I remember using BJTs at school. We used the BC109 or similar in a metal can package. They put them in holders, together with a base resistor to provide some protection. You could put them on a piece of strip board with wires, weave the wires though the holes for strain relief. Again, I don't see the point, since your time costs more.

[Nominal Animal]

I like using BC847C and BC857C myself (SOT23-3 = TO-236AB), as I can simulate them well using ngspice and they're dirt cheap (3-5€ for 100 at Mouser).

If you want a specific adapter board, say a 3-pin or 2×3-pin adapter for breadboard use with the PCB vertical, i.e. pins parallel to the PCB, straddling it, just design them and manufacture them at JLCPCB, PCBWay, et cetera!  I like designing them at EasyEDA, because it works in the browser (does require a network connection), and is really easy for a hobbyist type like myself for this kind of stuff; KiCAD is free and local and at least as good, but with slightly steeper learning curve (in my opinion).  At JLCPCB, one hundred 1"×1" boards costs you about 10€ + shipping.  So, we're talking about 30€-40€ investment for 100 NPN and 100 PNP BJT adapter boards.

SOT23-3 have typically limited maximum current and power dissipation, but there are many SMD packages with much better thermal and current characteristics.  Soldering those can be annoying, so you can use the assembly services to have the PCB manufacturer also assemble the boards (except for the pin headers, which you likely have to solder yourself by hand).  For breadboard use, use the backside as a (flat) heat sink with plenty of vias to the cooling pad of the transistor package, and consider using thermal adhesive to glue a small heatsink (those used for Raspberry Pi's and other small chips, typically 8×8mm to 12×12mm, height varies) on the back side.  It will be in electrical contact with the transistor cooling pad, but the thermal properties are pretty darn good.

There are a few tricks.  One is to do iterative development, and start with sets of five, and see if it can be improved before ordering a larger set.
Soldering pin headers parallel to the PCB works better, if you strengthen them with vias, especially vias-in-pad.  (The pad will of course be rectangular, about 1mm wide, at 2.54mm spacing.)  In my opinion, a zig-zag pattern of vias on each pin (at each edge of the pad) will strenghten the connection, so that one can push and pull the adapter to/from a breadboard from the PCB itself.  You might want to have the sides an indentation in the middle, for better finger grip. You might add a polyfuse to limit current, depending on the use cases.

If I can do it, anyone can.

[DavidAlfa]

Contrary to what you might thing, the TO220 thicker legs won't tolerate half the abuse of what the TO92 can handle.
Those legs like to bend at the base of the package, then it will always bend there, 2-3 times and the leg will fall off.

It is what it is, those litle devices will start breaking after recycling them several times when breadbording.
But they're for 2 cents at lcsc, so I don't see how the cost factor could be an issue.
https://www.lcsc.com/product-detail/Bipolar-Transistors-BJT_LGE-BC547B_C713613.html
https://www.lcsc.com/product-detail/Bipolar-Transistors-BJT_LGE-BC557B_C713617.html

[David Hess]

When I breadboard TO-220 packages, I solder little solid wire extensions onto the legs because they are just thick enough to "spring" the breadboard.

[Zero999]

When I breadboard TO-220 packages, I solder little solid wire extensions onto the legs because they are just thick enough to "spring" the breadboard.

For the benefit of the OP (I know you're aware of this) breadboard isn't rated to carry much current, typically under 1A, so it's not possible to use TO-220 devices at their full current rating.

[T3sl4co1l]

"Not possible" is a rather extreme statement.

I've put 5A, maybe even 10A through breadboards before.  They get rather hot when you do that at 500kHz.  That one needed extra jumper wires.

Have yet to turn a contact into a glow lamp.  Have melted far more positions due to overheated transistors than contact resistance.

I suppose I can't speak for the latest crud from China or elsewhere, but of what I've used, haven't exactly been top of the line name brands, either.

Nothing you'd use 24/7, or expect to work for much time, or frankly at all, unsupervised; but... that 100% describes solderless breadboards, right? You aren't using them as part of installed equipment, right?

Tim

[David Hess]

When I breadboard TO-220 packages, I solder little solid wire extensions onto the legs because they are just thick enough to "spring" the breadboard.

For the benefit of the OP (I know you're aware of this) breadboard isn't rated to carry much current, typically under 1A, so it's not possible to use TO-220 devices at their full current rating.

Without a heat sink, a TO-220 package can handle about 2 watts maximum which is easily achieved even with only 1 amp.  A small heat sink can extend this to perhaps 5 watts.

[Zero999]

When I breadboard TO-220 packages, I solder little solid wire extensions onto the legs because they are just thick enough to "spring" the breadboard.

For the benefit of the OP (I know you're aware of this) breadboard isn't rated to carry much current, typically under 1A, so it's not possible to use TO-220 devices at their full current rating.

Without a heat sink, a TO-220 package can handle about 2 watts maximum which is easily achieved even with only 1 amp.  A small heat sink can extend this to perhaps 5 watts.

Yes, breadboard can be safely used at voltages up to around 60VDC, which would be 60W, way above what a TO-220  I was trying to keep it simple, as this is the beginner's section.