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| Why is the 741 op amp still produced? |
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| TimFox:
When the analogous questions were asked in the Soviet Union in 1950, they appointed a commission to study the problem. See: https://www.cia.gov/library/readingroom/docs/CIA-RDP80-00809A000600330961-8.pdf |
| T3sl4co1l:
--- Quote from: coppice on September 22, 2020, 02:17:57 pm ---Only a very young and naive engineer, or an idiot, puts a semiconductor device into an industrial application without checking its life status..... unless its truly a one off project. Most industrial stuff stays in production for years, while most complex consumer parts appear and disappear at random, according to how well high volume purchases are going. --- End quote --- It's very easy to be tempted by $5 (and less) LCD displays, and powerful (if perhaps buggy, but hey, we can fix that in software, right?..) CPUs, and so on, and just say "if it drops, we'll respin the product with the next closest thing, it'll be fine"... It's no accident that there's an entire market built around extending the production lifetime of these products. Most of these sorts of things you'll find on Digi-Key and such, are targeted this way (as far as I know). You don't go on Alibaba to find some no-name LCD, you find the mature e.g. Newhaven Display, and yup, it costs four times as much, and often it's worth every penny. (Just spot checking a random part by Newhaven, I see 6-10 year estimated product lifetimes.) Tim |
| free_electron:
--- Quote from: Doctorandus_P on September 22, 2020, 01:20:20 pm ---Somewhat related to this: The Allwinner A10 (or was it the A13) is a now obsolete microprocessor. Olimex is an (apperently decent sized) customer of those chips, and they have customers who use them in industrial boards. I.E. Tested & verified, long term planning and such. On the Olimex website there is a long blog post about Alwinner re-starting the factory for those chips for a batch of 50.000 special delivery to Olimex. I do not know what the normal lifespan of a set of masks is. Did they dust of old masks for this, or just made new ones because they wear out after 50.000 chips? --- End quote --- 50.000 is going to be one batch of wafers. ( 25 or so if they run 300mm wafers) , so this is peanuts. Masks can expose millions of wafers without issues. so no problem at all. |
| David Hess:
--- Quote from: Wolfgang on September 21, 2020, 08:59:55 pm ---I would agree that the 358s/324s cannot replace the 741s in case crossover distortion is a big issue, but in other cases the advantages are obvious: - 2/4 instead of one in a single case --- End quote --- That brings up *why* true dual 741s were so expensive and it was simply because the integrated 30 picofarad capacitor takes up a lot of space. The 358/324 design only requires a 5 picofarad compensation capacitor because it was designed with transconductance reduction of the first stage making it suitable for dual and quad parts. What you are asking for is the 1458 which is a 741 designed with transconductance reduction making it suitable for dual and quad parts. --- Quote ---- more current --- End quote --- That requires larger output transistors and increased power dissipation compromises precision. There were a lot of high voltage and high current parts based on the 741 design but they were ultimately not economical. --- Quote ---- negative rail included in input and output, thats often enough. --- End quote --- Single supply and rail-to-rail outputs are feasible but complicate the design and the extra area increases the cost. Single supply and rail-to-rail inputs exclude input bias current compensation. Rail-to-rail inputs compromise common mode rejection. The above implies that there should be high performance precision parts with rail-to-rail outputs, and there are. --- Quote ---- cheaper --- End quote --- Anything which increases the area of the chip or increases the testing time also increases the production cost. --- Quote ---- slightly faster --- End quote --- There are plenty of faster (3 MHz) 741 equivalents based on the PNP input MC4558 dual and RC4138 quad. They are not true 741s, having PNP inputs means that their input bias current is reversed, but they were intended to have 741 performance except for being faster. |
| schmitt trigger:
--- Quote from: TimFox on September 22, 2020, 02:34:37 pm ---When the analogous questions were asked in the Soviet Union in 1950, they appointed a commission to study the problem. See: https://www.cia.gov/library/readingroom/docs/CIA-RDP80-00809A000600330961-8.pdf --- End quote --- Very interesting report. Nevertheless the Soviet Union managed to design many wonderful tube types and build them in large quantities. |
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