Goodbye TO92 bipolars. It's been nice. - Page 1
Forum section: electronics / general

author: rfclown
author_rank: Frequent Contributor
timestamp: January 19, 2021, 04:30:43 am
content: I've been using 2N3906/2N3904 and PN2222/PN2907 since I was a kid (45 years?). Now I go to Digikey/Mouser, and it looks like TO92 bipolars are a thing of the past.2N3906: obsolete2N3904: obsoletePN2222: obsoletePN2907: active (relief. I guess I'll design all PNP circuits from now on.)From Mouser I can get 2N3906s from Central Semiconductor if I buy a reel of 2000 and can tolerate an 8 week lead time.At least the SMT versions are available so I can still design with them. But it sure is nice to have the same parts in a leaded package so you can use solderless breadboards to test the circuits first (after simulation of course).

author: ledtester
author_rank: Super Contributor
timestamp: January 19, 2021, 04:56:09 am
content: Um, I just checked and Mouser USA has 10K ready to ship:https://www.mouser.com/ProductDetail/Central-Semiconductor/2N3906-PBFREE/?qs=u16ybLDytRb9MyqIeMhz0Q%3D%3D

author: rfclown
author_rank: Frequent Contributor
timestamp: January 19, 2021, 05:11:19 am
content: Quote from: ledtester on January 19, 2021, 04:56:09 amFrom Central Semiconductor. It's sad that ON is obsoleting them. ON bought Fairchild. ON was Motorola.From Central's website: "Central has remained dedicated to manufacturing many other trailing edge devices in legacy packages"

author: bdunham7
author_rank: Super Contributor
timestamp: January 19, 2021, 05:45:57 am
content: If you like your leads straight, they have 20,000 or so for you. If you want them bent, there's another 40,000 or so, from ON Semi if you must. Central is fine too.https://www.mouser.com/Semiconductors/Discrete-Semiconductors/Transistors/Bipolar-Transistors-BJT/_/N-ax1shZ1yzvvqx?Keyword=2N3906&FS=True&bws=1Same for your PN2222A.https://www.mouser.com/Semiconductors/Discrete-Semiconductors/Transistors/Bipolar-Transistors-BJT/_/N-ax1shZ1yzvvqx?Keyword=pn2222a&FS=True

author: Siwastaja
author_rank: Super Contributor
timestamp: January 19, 2021, 07:32:10 am
content: With niche technology, you can't be too picky. Why do you want a specific manufacturer? These parts have multiple good sources.

author: daqq
author_rank: Super Contributor
timestamp: January 19, 2021, 08:06:19 am
content: Not ideal, sure, but this sort of shift has been long coming. Frankly I'm amazed that anyone actually manufactures stuff like 74xx in DIP packages. It's been some time since I've actually seen them in a new design of even specialised stuff, let alone in a mass produced product.It's really great and practical for research, prototyping and hobby use, but for production I'd avoid it if at all possible.

author: fcb
author_rank: Super Contributor
timestamp: January 19, 2021, 08:46:28 am
content: If people don't buy 'em. Then people won't make 'em.When was the last time you saw a cooking transistor in a TO92 package?

author: magic
author_rank: Super Contributor
timestamp: January 19, 2021, 09:09:03 am
content: They are indeed listed as obsolete below, but these are the Motorola versions.https://www.onsemi.com/products/discretes-drivers/general-purpose-and-low-vcesat-transistors/2n3906I can't now find information about the Fairchild version (2N3906BU/2N3906TA IIRC), anyone knows?Quote from: Siwastaja on January 19, 2021, 07:32:10 amI'm not sure if TO92 transistors really have that manygoodsources. I mean, with a reasonably complete datasheet for example.

author: tooki
author_rank: Super Contributor
timestamp: January 19, 2021, 10:12:19 am
content: Quote from: rfclown on January 19, 2021, 04:30:43 amAll you've discovered is that specific versions get obsoleted.But the fact that thoseversionshave been obsoleted doesn't mean the part itself has been. On Semi is still making every single one of the models you listed. Youdorealize that the suffixes (like "BU" on "2N3904BU") simply refer to how the legs are formed and how they're packaged, right?Right?Straight or kinked legs, bulk, on tape (what size reel, they have more than one), etc. During the transition to lead-free, many products gained some identifier for the lead-free version. This is why DK has a "base part number" field on the device pages.In other words, you're absolutely, completely 100% wrong about these transistors becoming unavailable.Quote from: magic on January 19, 2021, 09:09:03 amActive: they're listed right on the website in the list of transistors:https://www.onsemi.com/products/discretes-drivers/general-purpose-and-low-vcesat-transistors/2n3904bu

author: MK14
author_rank: Super Contributor
timestamp: January 19, 2021, 10:19:00 am
content: Quote from: fcb on January 19, 2021, 08:46:28 amI don't really know the reason why (but high voltages, is still a possible advantage, for through hole components). But some finished consumer items, still seem to be produced, in huge quantities, and they are made with all through hole components.E.g. Fly Zappers.https://youtu.be/vvXZM6kg_gI?t=193Feel free to skip ahead, to around the 3 minute mark, to see the populated PCB:

author: magic
author_rank: Super Contributor
timestamp: January 19, 2021, 12:02:12 pm
content: Quote from: tooki on January 19, 2021, 10:12:19 amNo, he's right. BU/AT are inherited from Fairchild with separate datasheet and made on a different process. The old Motorola part appears to be legitimately gone. Dunno if anyone will miss it, though.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 19, 2021, 01:52:43 pm
content: Think I use SOT23s more for prototyping than TO-92s. Really only use them on the solderless breadboard.Tim

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: January 19, 2021, 01:57:16 pm
content: Digikey list 127 TO92 NPN bjts, >10K stock on many of them

author: rfclown
author_rank: Frequent Contributor
timestamp: January 19, 2021, 02:10:50 pm
content: Quote from: mikeselectricstuff on January 19, 2021, 01:57:16 pmYou're right. I missed it by the newer Digikey search listings. I flew past the "TO-226-3, TO-92-3..." stuff and just selected the things that started with TO-92. Then I went to ON's site, searched on "2N3906", clicked the first link, and everything in the list was obsolete. I reacted too soon.

author: tooki
author_rank: Super Contributor
timestamp: January 20, 2021, 04:25:01 pm
content: Quote from: magic on January 19, 2021, 12:02:12 pmBut what does that matter, given that they’ve always been equivalent parts?And besides, the thread title is “ Goodbye TO92 bipolars. It's been nice.” and it’s categorically untrue that TO-92 BJTs are gone.

author: bdunham7
author_rank: Super Contributor
timestamp: January 20, 2021, 04:28:13 pm
content: Quote from: magic on January 19, 2021, 12:02:12 pmWhat is the basis for that statement? Can you link the 'different datasheets"? I don't see these as anything other than packaging options.

author: jmelson
author_rank: Super Contributor
timestamp: January 20, 2021, 04:31:47 pm
content: Digikey appears to be in a plan to go out of business, or become the next alibaba or Amazon of the electronics world. I get part life notices for all sorts of stuff I have bought from them saying the part has been obsoleted by the manufacturer. I go to other sites to confirm, and there is no indication the part is going out of production. So, it appears Digi-Key is lying, and they just chose to no longer stock that part. This is really sad, as Digi-Key used to be a great distributor. I think their plan is to not stock anything, and become a middleman for their "partners". What with the counterfeit issue, there is NO WAY I'm going to buy parts that way.Jon

author: rsjsouza
author_rank: Super Contributor
timestamp: January 20, 2021, 04:38:26 pm
content: Ah, it is similar to Tequipment then. I always found their practice of saying that a product was "discontinued" when in fact they just don't sell them anymore. I hate that.

author: drussell
author_rank: Super Contributor
timestamp: January 20, 2021, 04:58:45 pm
content: Quote from: rfclown on January 19, 2021, 02:10:50 pmYou know that, for now, you can turn off the "new, modern search" on digikey in thesettingsbutton in the upper right hand corner, right? Their database is still getting seriously messed up with terrible categorizing on the picklists, etc. and I'm still not sure why they're hell bent on turning into an electronic Amazon also-ran, but at least the old style is still available for now and is still slightly less annoying than the new interface.

author: drussell
author_rank: Super Contributor
timestamp: January 20, 2021, 05:00:48 pm
content: Quote from: rsjsouza on January 20, 2021, 04:38:26 pmWhat is a a distributor that stops stocking something supposed to say other thandiscontinued?I suppose it would ideally be nicer to specify "No Longer Stocked" vs "Discontinued by Manufacturer."

author: tooki
author_rank: Super Contributor
timestamp: January 20, 2021, 05:41:07 pm
content: Quote from: drussell on January 20, 2021, 05:00:48 pmWhich is exactly what they do: “obsolete” is when the manufacturer obsoletes it. “Discontinued at Digi-Key” is for when they choose to stop carrying a non-obsolete part. jmelson is probably confusing another distributor’s slowness in updating their part status.The other thing is that DK meticulously keeps manufacturer part numbers separate. So if the manufacturer decides to, say, change from reels of 2500 to reels of 3000, which will have a different part number, then the 2500 will become obsolete even though the part as such hasn’t changed status.

author: magic
author_rank: Super Contributor
timestamp: January 20, 2021, 06:12:31 pm
content: Quote from: bdunham7 on January 20, 2021, 04:28:13 pmMotorola:http://www.farnell.com/datasheets/1758684.pdfFairchild:http://www.farnell.com/datasheets/1880984.pdfThey are similar and both no doubt meet the registered specs of the part number, but on close inspection you may see some differences in typical specifications. Notably, Fairchild has flat beta with collector currrent and it appears to extend down to very low currents. AFAIK technology for that has been developed by the Japanese for analog applications like Hi-Fi and then spread to Korea and Fairchild ended up buying a bunch of fabs there in the '90s.

author: rsjsouza
author_rank: Super Contributor
timestamp: January 20, 2021, 06:58:21 pm
content: Quote from: drussell on January 20, 2021, 05:00:48 pmExactly. These terms describe the intent in a better fashion.

author: drussell
author_rank: Super Contributor
timestamp: January 20, 2021, 07:16:37 pm
content: Quote from: drussell on January 20, 2021, 05:00:48 pmReplying to my own post here, of course, but...What I would really like to see more careful attention payed to is the "superseded by" aspect, which would quite often provide a more obvious path to possible replacements, other variants or substitutes. (Obviously without getting too far down thesubstitutionrabbit hole like NTE or something, that is...)Like, yesterday I was looking up the TOP247Y switching controller in my Ryobi P125 charger. The TOP247Y isobsoleteand discontinued so there are none in stock anywhere of course, but when I go back up into the main category and do a complete search, of course I can easily find that the TOP247YN (No Lead, ROHS) is still available just "not recomended for new designs" as there is a newer HX series 257 with better parameters for new designs, but the old series 247Y or beefer 248Y and 249Y are still readily available if I do end up needing to change it out. There is just nothing on the 247Y page that points me to the 247YN page, which would be a convenient direct link to have to prevent the essentially wasteful time spent sleuthing the other "obvious" variant.It is very correct and actually critical for them to be careful to not intermingle manufacturers' part numbers which are different whether that be ROHS compliance on the lead finish or lead spacing or reel size or whatever. Sometimes these things matter and they arenotalways necessarily equivalent but it would sometimes be potentially useful to have an obvious link to similar familial parts in some cases if implemented properly, especially on "manufacturer discontinued" parts.

author: rsjsouza
author_rank: Super Contributor
timestamp: January 21, 2021, 02:00:03 am
content: Yeah, that I don't understand; if properly placed on the page and maintained with relevant hits, having related links are really effective to increase sales.

author: HwAoRrDk
author_rank: Super Contributor
timestamp: January 22, 2021, 03:33:23 am
content: In my experience, when a distributor marks a part as 'obsolete' or 'discontinued', they mean one of several possibilities:1. Thatexactp/n is no longer produced, but the part is still being made under a new p/n variation (due to, e.g. new process/factory/package).2. The partisactually obsoleted by the manufacturer, but the manufacturer is lying about it being 'active' on their website. Perhaps because they're willing to produce more if they get a big enough order.3. The distributor just doesn't stock it anymore, but tags the listing inappropriately.Of course knowing which is true is an exercise left for the hapless purchaser-to-be.

author: ebclr
author_rank: Super Contributor
timestamp: January 22, 2021, 08:33:10 am
content: https://pt.aliexpress.com/item/32861544117.html?spm=a2g0o.productlist.0.0.4a966b12RkH77x&algo_pvid=931bbc8e-b56d-4c1e-9d20-73b30cd94c86&algo_expid=931bbc8e-b56d-4c1e-9d20-73b30cd94c86-7&btsid=0bb0623d16113043615604299e6660&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_