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I've noticed that many retailers still sell 74HC logic gate chips, which I also used in my digital design class. I'm curious to know whether these older components are still profitable for chip makers and whether they are still widely used in industry.

JRE
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hskim
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1 Answers1

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It is hard to tell in general. If you meant the classic 74HC family in plastic DIP through hole packages, often used in school/university educational labs, they are more or less obsolete.

They have a (small) niche market for educational labs, for they are easily breadboardable, and another (somewhat bigger) niche as spare parts for old industrial control boards, which may have a long service life (decades) due to their (somewhat huge) initial engineering costs (for example, think of the control boards for nuclear reactor plants: they are designed ad-hoc for that specific plant and their design is not meant to be easily reused).

To my knowledge, the only major manufacturer that still has them in its catalog is Texas Instruments. The fact they have them in their catalog means they are somewhat profitable. It is well possible you will pay a premium to get a batch of them directly from TI, though.

A search on digikey for 74HC active parts under the category of "gates and inverters" filtering for "through hole" shows that there are few manufacturers producing them. However if you click on the datasheet links you'll find that only TI has updated datasheets (2020 or later) with ordering information clearly stating the PDIP packages are active products.

OTOH, if you meant the 74HC family in general, it is still widely available from many major vendors in SMD packages, although it is not used in design so much nowadays and many very specialized parts are not produced any longer.

74HC family is still useful because it is a very mature technology and it is not extremely fast, which seems counterintuitive, but in design you shouldn't use parts that are too fast for the job at hand, since designing with faster parts brings up a lot of problems which you wouldn't want to cope with if it is not necessary.

LorenzoDonati4Ukraine-OnStrike
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  • Thanks for the answer. It's amazing that these classic technologies are still useful in an era where transistors can be made on a few nanometer scale. It would be really fun to visit the manufacturing lines that produce these components.

    As someone who was a undergraduate student in electrical engineering, I'm really grateful that I can still buy these basic components. If these components were completely discontinued, we might have to extract components from old radios for our university classes.

     – hskim Apr 02 '23 at 10:18
  • @hskim It is for flexibility. You would not put 100 nanoscale transistors onto a circuit board for your product. It costs about 1-10 million dollars to make a custom chip at all so if you're only going to make 100 of this specific circuit board, that's upwards of ten thousand dollars a board. However, I would wonder why they haven't been replaced by microcontrollers and CPLDs, which can also serve this purpose. – user253751 Apr 02 '23 at 10:25
  • @hskim Probably the best way to go is starting to teach how to solder SMD components and organize educational labs so that SMD chips are soldered on adapter boards with pin headers suitable for breadboarding. I really doubt TI will keep on producing them, say, 30 years from now (as old industrial plants/machinery with TH parts are retired from service). As far as I know TH logic hasn't been widely used in new designs for at least two (maybe three ?) decades now. – LorenzoDonati4Ukraine-OnStrike Apr 02 '23 at 10:25
  • @hskim As inconvenient as this may be for the student, clinging to such a vanishing technology might involve skyrocketing costs for educational institutions. I have practical examples for this: in my school there are (or have been) colleagues that still ordered uA741 opamps and 2N2222 transistors for their lab classes, just because they have been teaching with those parts for 20+ years. They never realized (or wanted to) that they were paying them even 10 times more than, say, more available parts like LM358 opamp or PN2222 BJT (which is essentially a 2N2222 in TO92 package)!!! – LorenzoDonati4Ukraine-OnStrike Apr 02 '23 at 10:31
  • @LorenzoDonatisupportUkraine Haha that makes sense but I would have students to use SMD to to DIP socket. I have seen many students became to dislike digital design lab just because of the soldering (though soldering was one of the great parts for me) – hskim Apr 02 '23 at 10:34
  • Yeah, my professor also still uses those classic components. Students had to use UV light to re-write the EPROM – hskim Apr 02 '23 at 10:37
  • @hskim The soldering hurdle can be bypassed with organization: more expert students or TAs might assemble the chip carriers for newbies, who would then just use the chips on the breadboard from the start. In parallel they may be taught how to solder SMD chips. The problem may be more acute for older people, like professors: learning how to solder SMDs requires a firmer hand and better eyes! ... – LorenzoDonati4Ukraine-OnStrike Apr 02 '23 at 11:13
  • @hskim ... For youngsters it's just a matter of practice and it's a skill that it's more appreciated in the industry than breadboarding. In fact most industry prototypes are never breadboarded nowadays (at least not solderless BBs, protoboards are still a thing). – LorenzoDonati4Ukraine-OnStrike Apr 02 '23 at 11:13
  • @user253751 It depends on the scale of the project. For a mass produced gadget with no particular safety requirement, it may be cheaper to use a single chip solution. But programming a MCU or a CPLD requires specific skills and design techniques, which may increase non-recurring engineering costs, especially if your board has to be certified. In fact you'll also need to certify the software sometimes. And SW is not all that reliable in every case, Moreover sometimes you need some glue/interface logic for a MCU design which cannot be done with CPLDs (e.g. a line driver or a load driver). – LorenzoDonati4Ukraine-OnStrike Apr 02 '23 at 11:23
  • @hskim "Students had to use UV light to re-write the EPROM" OMG (* palm face *) I can feel your pain! ;-) That's putting a new meaning to the word "obsolete" :-) – LorenzoDonati4Ukraine-OnStrike Apr 02 '23 at 11:28
  • @LorenzoDonatisupportUkraine Nah, microcontrollers are ubiquitous. CPLDs not so much but they're still pretty cheap. – user253751 Apr 02 '23 at 16:45
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    @user253751 MCUs are indeed ubiquitous, but the skills to program them for safety-critical applications are definitely not. – LorenzoDonati4Ukraine-OnStrike Apr 02 '23 at 17:07
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    In MCU-controlled data acquisition, I often find that I need just a little "glue" logic. 74HC is perfect for this: fast enough, but not so fast that it's electromagnetically touchy. – John Doty Apr 02 '23 at 23:24