There is a wide range of 'classic' IC's that have been in production 25-30 years. Aside from working well in many applications, you can find them anywhere. And yes, there are improvements on them in the market.
People tend to use what they understand, or have mastered, or are too lazy to change so long as it works. The 741 or 555 type devices are proof of that.
I have an HP 11C which works perfect in every respect. I bought it about 10 years ago from a Nephew who had no idea what polish notation was. I always wanted one of them but wasn't willing to pay the price and settled on the TI SR-56. I'm going to try the electrolytic cap to see if it will still work.
Ti calculators are very good. They have a wide range. The development at TI for calculator products are going hand in hand with teaching curriculam and so they are successfull. Also they update and retain the best models sold in the past time.
to the mm5316 data sheet is in error.
Still use my Casio College Fx 100 bought in 1986 - both my kids have unsuccessfully tried to destroy it by sitting on it, throwing it around and once dipping it in a bucket of water. Works every single time it is switched on! Thanks to the engineering teams at Casio for other goodies like my databank wrist watch and the film watches as well.
Thanks Barrie--your special perspective is always welcome! And the AD574 "complete" 12b ADC IC is still available (even in a DIP package), with a new die, but it is form, fit, and functionally the same after 30 years (though specs of the newer versions are somewhat better, I believe).
I still have a nice HP-41CV which runs a compact
version of "Supreme" - the semiconductor (device
design) simulation program. I can't say I use it,
now that we have so much arithmetical power (not mathematical power) now beneath our teenie-tiny fingers; but since it is complete, with original case and instruction booklet, even the original box - all in pristine condition - I'm keeping it for display in my private museum along with spark-gap transmitter, crystal sets and radios from the first quarter of the last century - most of which still work as well as they did when first purchased.
But then, I have ICs I designed for ADI back in the 1970s that are still in the catalog, making solid contributions to the bottom line. I expect the same can be said of the 555 (although the AD537 is a far better part...) and the uA741 - though surely with so many excellent and cheap op amps out there, I find THAT surprising.
One can readily buy all manner of vacuum tubes, on eBay, for example: but they are not the first thing that springs to mind when about to invoke the (dubious "high-gain") claims often made for todays' op amps... oh,,, you mean DC gain. Yeah, but that's rarely important.
On the other hand, I am currely resurrecting the analog computer theme, using Philbrick K2-W op amp modules (2x12AX7s) whose open-loop DC gain is an embarrassing x1,000 and whose input offset of 1.5V makes one wonder how anyone could ever make a decent computer out of them...
Person who repaired them may be retired or he may have moved to better opportunity. Training new person for very week demand and maintaiing tools, test systems is very expensive affair.
They refuse not only the simple calculator, but the refuse systems used in F-15 fighter aircraft and many other defence hardware. But some afficiondos do purchase and keep them in quantity when they get last buy notice.
Still using my HP 15C and don't know what I would do without it. Just for a backup I bought a newer model, the 35s. I had to go and get it out of its cover to see what the model was, and I see the two lithium coin cells have already failed!
I do miss my "Woodstock" series HP25, with the LED display. Despite its limited functionality, it was a "gateway" to a potential life of programming: after I got it I spent two full weeks writing programs, and finally utterly exhausted its capabilities. Friends who got the HP65 and later the HP67 in some cases became consumed with the things, spending man-years writing programs which they insisted were going to be so useful once perfected.
But I went back to circuit design, knowing that I didn't want to become a programmer.