General > General Technical Chat
Why is the 741 op amp still produced?
coppice:
--- Quote from: David Hess on September 28, 2020, 11:13:00 pm ---Getting supplies like wafers for old processes is a problem also.
--- End quote ---
I suspect that sourcing small wafers for old fabs only becomes a problem when the last small wafer fab closes. The problem is the cost per square mm will be higher, as it becomes more of a specialist product.
David Hess:
--- Quote from: exe on September 29, 2020, 11:17:55 am ---
--- 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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No, why would it compromise reliability? That is how the parts are tested in the first place.
For a 44 volt 741, I would test the voltage follower configuration over the common mode input range while measuring the supply and input bias current at low and high temperature, for hours to days.
--- Quote from: coppice on September 29, 2020, 12:09:01 pm ---
--- Quote from: David Hess on September 28, 2020, 11:13:00 pm ---Getting supplies like wafers for old processes is a problem also.
--- End quote ---
I suspect that sourcing small wafers for old fabs only becomes a problem when the last small wafer fab closes. The problem is the cost per square mm will be higher, as it becomes more of a specialist product.
--- End quote ---
No, what I described has already happened even decades ago; old but popular parts may be redesigned for manufacturing on a new process simply because wafers for the old process are no longer available.
floobydust:
Are we saying there's been no improvements in analog IC technology? We should settle for 5V parts or just eat the 10x price hit to beat the 741's "features"? :rant:
I saw National Semiconductor's standardized processes, high voltage (even to 170V) bipolar with better feature size, speed.
I think you can do more with less silicon when you take these old parts and move them to modern, standard processes. We could compare 741 die shots to see how much it has shrunk.
National Semiconductor Develops New Complementary Bipolar Process
A Complementary Bipolar Technology Family With a Vertically Integrated PNP for High-Frequency Analog Applications
T3sl4co1l:
What do you mean no improvements? We can do a heck of a lot more in 3.3V and less, than was ever possible in +/-15V or more, back in the day. Mainly because we aren't limited in complexity by keeping everything analog. The only place the voltage and current matter are where it touches the outside world; inputs can be divided down with precision resistors, leaving power output the last remaining at-scale, fully-analog challenge. The higher cost of which is easily justified by the much greater overall functionality, no?
Tim
rstofer:
My Comdyna GP-6 analog computers are full of 741s, The model in the metal can which costs about $13 at DigiKey.
https://www.oldcomputermuseum.com/comdyna_gp6.html
https://www.digikey.com/product-detail/en/texas-instruments/LM741H-NOPB/LM741H-NOPB-ND/148206
I suppose I could substitute more modern op amps but I won't. I have two of the GP-6s to maintain.
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