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If I buy an MMBT4401 from Diodes, Inc., I get a 40V, 0.6A NPN transistor in a SOT-23 package. If I buy an MMBT4401 from ON semiconductor, I get a 40V, 0.6A NPN transistor in a SOT-23 package. If I buy an MMBT4401 from Micro Commercial Co,... you get the idea. And this is hardly the only case of this; countless companies make 1N400x diodes, 2N7000 NFETs, 2N3904/MMBT3904 transistors...

I'm quite certain that these companies don't all share the exact same silicon (though some of them might be packaging and reselling silicon dice bought from the same source), so what exactly is standardized between them? Is there even a de jure standard (and if there is, who sets it), or is this all just a de facto standard?

In either case, which specific figures of merit are considered "part of the standard"? Can I trust that no 1N4001 will have a forward voltage greater than some standard value, for instance? That one I'd be pretty sure is part of the standard, but what about the parasitic series resistance? I know I wouldn't want a 1N4001 if it had a parasitic resistance of 10 ohms, but could such a diode be made and still bear the mark 1N4001?

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  • \$\begingroup\$ In the particular case of the 1N4001, all suppliers give it a half-cycle surge handling of 30A, which needs R << 10 ohms. A particular egregious case is the TLV431. The ONSEMI and DiodesInc versions handle 16v, the TI version only 6v. That's the only gross difference between suppliers that I'm aware of. Read those datasheets as Marcus suggests. \$\endgroup\$
    – Neil_UK
    Commented Sep 29, 2019 at 15:46
  • \$\begingroup\$ There are small local patterns in the part numbers here and there. But there are very few [and I'm not aware of any] rules that apply across multiple vendors. If there's a part number pattern which applies across multiple vendors, that's usually because vendor B wants to signal that his part is compatible with a similar part from vendor A. \$\endgroup\$
    – Nick Alexeev
    Commented Sep 30, 2019 at 1:49

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A very few components are actually standardized by JEDEC (think of the 7400 logic series, for example).

Most of the components you mention are simply results of historic multi-sourcing agreements: Large customers (esp. of the military kind) wouldn't buy an obscure part that they could only get from one party.

Also, don't underestimate the history of these companies: for example, TI having all the parts that are still available in stock under the brand name of National Semi happens because the former bought the latter, and some stocks simply have a half-life of roughly eternity. Mergers and spin-offs sometimes leave multiple parties with access to the same IP.

To answer about guarantees: Um, these usually don't exist. Good luck out there and read your datasheets!

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  • \$\begingroup\$ Hmm. Not a very satisfying answer, I'm afraid, but it makes sense. It'd be nice if there was some kind of cross-manufacturer minimum standard for generic parts... \$\endgroup\$
    – Hearth
    Commented Sep 29, 2019 at 15:42
  • \$\begingroup\$ @Hearth Who would enforce it and how could it be enforced? \$\endgroup\$
    – Spehro 'speff' Pefhany
    Commented Sep 29, 2019 at 15:48
  • \$\begingroup\$ @SpehroPefhany I'm an engineer, not a... whatever you'd call the sort of person who does that stuff! \$\endgroup\$
    – Hearth
    Commented Sep 29, 2019 at 15:53
  • \$\begingroup\$ @Hearth stating intentions that have far-reaching legal consequences? Hopefully, that's called a corporate lawyer... \$\endgroup\$
    – Marcus Müller
    Commented Sep 29, 2019 at 16:29
  • \$\begingroup\$ @MarcusMüller Lawyer, legislator, whatever the word is, I'm not one of them. \$\endgroup\$
    – Hearth
    Commented Sep 29, 2019 at 16:36
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I’m not intimate with all the details of lapsed patented designs and cross-licensed designs but I’m pretty sure the part numbers you mentioned have all expired their OEM copyrights and unless guaranteed by design ( not tested) these specs must be universal for each package. Construction and protection may vary.

These guaranteed specs are the details defined in the datasheets in tables with environmental and process limits, while the graphs for nominal are not guaranteed. They apply only to the manufacturer and the Design Engineer must ensure any alternate source in the “approved parts and suppliers list” aka AVL , —the new must meet your design requirements. You cannot always assume, even if most are the same.

The exception is if you know there is no critical difference in your requirements, you may specify any source, but pro’s take sub’s seriously.

Enforcement is only by specs, PO’s and the buyer’s financial clout.

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