SOT-23 Pin-Out: base and emitter are inverted

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“hey stop, something ambiguous here, let’s check more deeply”

I believe that this( yours ) inner voice is there now, and that the next time that you will start modifying anything you will probably hear it screaming… :slight_smile:

If not all, then surely most of every PCB designer has been in your position at least once.

70+ posts, on a topic for a 3pin symbol, seems really funny to me now, honestly.

Headache for the library maintainers. For sure. Maybe not immediately, but at some point will do.

Once again, we( librarians ) are trying to keep the official libraries production ready.

When you are modifying things, you ought to check for breakage.

You also ought to verify “third” party content when you choose to make use of that.

We decided that( for our sanity )we will push some flexibility over to the symbol side.

I mean, it’s not a great issue to have both of them.

Maybe to you, but we are not that many people to afford introducing every possible variant in every possible way just because some manufacturers are making our “life” harder.

After all, KiCad’s library is a great great sample library for someone to start with.
It has bugs, known and unknown, it is getting better and better but not as fast as one might want.

I only have one solution. Get involved.

I really really do not want to waste more time on that cursed SOT-23. Can we please move the discussion to SOT-23W? Or to TSOT-23? :stuck_out_tongue: Just kidding, those last mentioned are not IPC compliant AFAICT, but i am out now. :slight_smile:

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Right, but a EasyEDA has it (if you check the JLCPCB component I linked, there is the footprint for EasyEDA. that footprint was also ignored but just because I don’t use EasyEDA :slight_smile: ), there is nothing preventing KiCAD to have t as well … since it’s way better than EasyEDA under many points, it can be also in this.

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Indeed :slight_smile:

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No problem

to me the most important things are the most important footprints combinations available.

they are not infinite. But once they are in it, the system is mor reliable.
Where with the word “reliable” I mean: it helps you to stop just in time, before you can make induced errors.

At the en it’s an instrument. As it, it should help you preventing things, like in many things it already does.

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Now, yes.
But during first 10…20 posts I even didn’t know that symbol was taken from KiCad based on the transistor name. Writing post 13 I was sure that in KiCad library you have NPNs only in Device library and simply wrong one of Q_NPN_BEC,… was selected and used.
I’m just not familiar with KiCad libraries. I have seen them few weeks in 2017 and since then I see only my libraries. I load KiCad libraries to be able to copy from it some footprints (but I do it by copying file by its name). Only copied footprints I see and symbols never. During this thread I for the first time run V7 with default configuration. to search for 2N3904.

It looks that you assume that you have to have the same pin numbers as in datasheet what is not my assumption. I have nothing to have my numbers different than in datasheet. In this case I would just used symbol with pin numbers correct for standard SOT23 footprint ignoring the datasheet numbering and really I would probably used MMBT3904 (even not accessible) as more standard (more manufacturers use that symbol) and in BOM listed several substitutes (including 2N3904S). It is not unusual that for some elements I list 5 or more substitutes. Sometimes substitutes works only in one direction. I have in BOM part A and list that it can be replaced by part B, but in another BOM I have part B and it can’t be replaced by part A.

I don’t expect problems from it. When PCB is designed correctly than who cares about pin numbers (I don’t have them (for transistors) at schematic and during 20 years before KiCad I had pad numbers switched off while designing PCB.

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Probably it will not be problem for you. I’m thinking about a situation where for example one person creates a library part and later someone else who is less experienced uses it, looking at the datasheet and thinking “hey, there’s something wrong” and uses another hour to wonder what to do with it. In a worst case scenario fixing it which again introduces a possibility of a new bug.

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yes it’s a must. Not an option. Since the Datasheet is your “bible” when you design. And up there pin numbers are declared not for sport and not because engineers didn’t know what to do or to add graphically. Consistency 1 to 1. Except for generic symbols then there are already the combinations.
And how these were created, there is nothing forbidding to be consistent also with foot prints.

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Not for me.

So if you used NXP:MMBT3904:
https://www.mouser.pl/datasheet/2/916/MMBT3904-1365817.pdf
you can’t replace it with MCC:MMBT3904:
https://www.mouser.pl/datasheet/2/258/MMBT3904_SOT_23_-2510634.pdf
just because manufacturer used different way of identifying footprint pads?
Sounds at least surprising for me.

Agree (95%) if you mean electrical parameters and not agree if you mean pin identification method.
Only 95% as datasheets nowadays frequently contains errors (30 years ago datasheets were better).
If one WIZNET datasheet says to use at VCC 10.1uF capacitor will you be searching to buy it because datasheet is a ‘bible’? I suppose that one analog guy said them to connect 100nF + 10uF and than someone (knowing that when you connect capacitors in paralel you get the sum of capacitances) replaced it with information to use 10.1uF.
When in 2014 I was selecting one DCDC IC to use the effect was TI decided to update all 9 datasheets I read during my searching just because I send them the list of errors in their calculations.
Few years later looking in one ST LM317L datasheet it was clear that someone ^C^V it from the higher current LM317 and not updated differences between them.

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86

There is another suggestion… Without inflating the library, add a function to the Landing Revenge Generator…

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No idea what you’re referring to but if for the nixies no footprints existed in the standard library. In fact I wanted to make my own to control the pad sizes, the circle radius and other things. :woman_shrugging:

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I am writing through the translator so clumsy)) Add this function (number selection) to the kicad footprint generator

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There’s no need. The wizard allows both circle directions. Landing Revenge Generator, hahaha. :wink:

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The best part is that neither datasheet describes the key issue, which is how the bulk parts are orientated on the tape reel. I would hate to have to setup pick and place machines

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This is the usual work of the smt line operator Placement is one of the easiest work))

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With 90 posts on this discussion, I am not sure that my added one will help much. But my take-away is that the SOT23 pin numbering may (unfortunately) vary. With most ICs you can usually rely on counterclockwise pin numbering that starts in the lower left. For the SOT23 package however, the pin numbers should be regarded only as an intermediary. Make sure that the physical location of the base, emitter, and collector agree with the datasheet.

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I used that assumption also for SMD diode bridge and marked as 1 lower left pin (according to picture in datasheet, as there were no numbers). It worked until the other manufacturer bridges were assembled. :frowning:

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My question is: do you really read what i do write?
If YES then you should now the history about the MMBT and do not put back into the game any longer. Since it hasn NOT any sense.

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Pin numbering is fundamental to have it.

It is like to get rid of the pin numbering of ICs …

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This mystery is solved and the discussion is just going around in a circle.

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