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Why is the 741 op amp still produced?
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exe:

--- Quote from: coppice on September 28, 2020, 01:39:53 pm ---it will be a redesign from scratch.

--- End quote ---

I recall reading that TI shrank their opamps two or four times, but I can't find any die shots to confirm this.
coppice:

--- Quote from: exe on September 28, 2020, 01:58:09 pm ---
--- Quote from: coppice on September 28, 2020, 01:39:53 pm ---it will be a redesign from scratch.

--- End quote ---

I recall reading that TI shrank their opamps two or four times, but I can't find any die shots to confirm this.

--- End quote ---
In the early days the geometries were enormous. Devices could be shrunk quite a long way before people had to worry about how to maintain a high voltage tolerance. And they were shrunk. Quite often. While trying to avoid letting customers know how much things had changed, as it might worry them. Until characteristics changed, designs in production broke, and they had to quietly admit to specific customers what was going on. I went through this a couple of times in the 1970s.
magic:
They also do apparently migrate them to new processes on larger wafers from time to time. They discontinued a big chunk of National's audio line a few years ago quoting this very reason. Several TI dice on zeptobars show timestamps from the '90s or 2000s, no idea what was that which they replaced.

As for opamps, I kinda assume it's bipolar unless stated otherwise. I have been hearing that bipolar tends to give more practical gain in analog applications. Also remember reading propaganda from National which claimed that complementary bipolar is advantageous over CMOS at high speeds because base width is controlled by diffusion depth rather than lithography resolution, which is cheaper to produce. That was a paper from the 2000s, though.

OTOH, low power, low input bias, outputs reaching within a few mV of the rails - that smells CMOS.
David Hess:

--- Quote from: coppice on September 27, 2020, 11:57:57 pm ---It will be interesting to see what happens to these higher voltage parts as less and less fabs remain functional which can produce them.
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There will be industry consolidation until all analog ICs are made by Texas Instruments.


--- Quote from: Zero999 on September 28, 2020, 07:53:43 am ---Not all '741s are rated to 44V. The LM741C is only rated to 36V maxium.
--- End quote ---

Nothing stops you from testing and grading your own LM741Cs for a 40 or 44 volt operation.  Tektronix used to do exactly this for some reason.


--- Quote from: coppice on September 28, 2020, 01:39:53 pm ---Making them forever is exactly the problem. Ancient analogue fabs are shutting down because they are so old people can't get spares for them any more. It looks like the remaining ones are only being kept alive through the reuse of parts taken from the ones closing down. Nobody is going to invest in new plant for tiny wafers, so a redesign for a process that exists for large wafers is usually needed. The original designers have probably retired, and the original design data has rarely been kept intact, so it will be a redesign from scratch.
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Getting supplies like wafers for old processes is a problem also.  You may have to buy the manufacturer of your wafers if you want to keep them available, and then what if they were also supplying your competitor?
exe:

--- Quote from: David Hess on September 28, 2020, 11:13:00 pm ---
--- Quote from: Zero999 on September 28, 2020, 07:53:43 am ---Not all '741s are rated to 44V. The LM741C is only rated to 36V maxium.
--- End quote ---

Nothing stops you from testing and grading your own LM741Cs for a 40 or 44 volt operation.  Tektronix used to do exactly this for some reason.

--- End quote ---

Doesn't this compromise reliability? How to know if they can sustain this for prolonged period?
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