Author Topic: Why is the 741 op amp still produced?  (Read 19658 times)

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Offline coppice

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Re: Why is the 741 op amp still produced?
« Reply #50 on: September 22, 2020, 10:14:08 am »
However, if you ask someone at TI to recommend a simple low performance cheap op-amp they'll probably recommend an LMV321, or an LMV324 is you need several amps. Note than the LM321 is about as old as the 741, but most people use the more flexible LMV321 derivative these days. Nobody recommends a 741 any more, but a lot are still used in equipment whose design hasn't changed for decades.
How is the LMV321 more flexible, than the old LM321? It has some advantages: lower power consumption, bias currents and a rail-to-rail output, but the fact it only works up to 5.5V, rather than 30V, severely limits its applications, making it inflexible compared to the old LM321.
The supply voltage limitation hardly limits it at all in practice. In most modern designs people aren't looking to operate from 32V. They are looking to get great results from a 3V to 5V supply. The LM321 says it operates from 3V to 32V, but at 3V its performance is terrible. The LMV321 is described as rail-to-rail, which is always a bogus description, but it gets reasonably close. One of the things you have to watch out for with the LMV32x is that they are generic part, available from many suppliers, but some are closer to rail-to-rail than others. If you want flexibility in sourcing parts you need to ensure your design can work with the worst of them.
 

Offline free_electron

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Re: Why is the 741 op amp still produced?
« Reply #51 on: September 22, 2020, 12:38:57 pm »

We can thank the audiophiles for that. Of course, they're not really after better audio quality when they use tubes, they're after making it sound like the way they remembered it back in the day.
like when they were 30 years younger and their hearing was better than now ...
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Offline TimFox

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Re: Why is the 741 op amp still produced?
« Reply #52 on: September 22, 2020, 12:45:42 pm »
Everybody agrees that the music in the 1960s was better than what followed--probably because of the Allen-Bradley carbon composition resistors.
 

Offline Doctorandus_P

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Re: Why is the 741 op amp still produced?
« Reply #53 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?
 

Offline coppice

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Re: Why is the 741 op amp still produced?
« Reply #54 on: September 22, 2020, 02:17:57 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?
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.

50k parts is a very small run. The masks, processes, packing and test facilities are almost certainly still available. The device isn't that old.
 
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Offline TimFox

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Re: Why is the 741 op amp still produced?
« Reply #55 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
 
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Offline T3sl4co1l

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Re: Why is the 741 op amp still produced?
« Reply #56 on: September 22, 2020, 04:35:06 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.

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.)

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Offline free_electron

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Re: Why is the 741 op amp still produced?
« Reply #57 on: September 22, 2020, 05:19:51 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?
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.
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Offline David Hess

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Re: Why is the 741 op amp still produced?
« Reply #58 on: September 23, 2020, 02:01:32 am »
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

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

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.

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

Anything which increases the area of the chip or increases the testing time also increases the production cost.

Quote
- slightly faster

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.
 
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Offline schmitt trigger

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Re: Why is the 741 op amp still produced?
« Reply #59 on: September 23, 2020, 02:02:21 am »
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

Very interesting report.

Nevertheless the Soviet Union managed to design many wonderful tube types and build them in large quantities.
 

Offline peter-h

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Re: Why is the 741 op amp still produced?
« Reply #60 on: September 23, 2020, 08:49:58 am »
I would say the proliferation of so many different parts is mainly due to chip makers trying to trap inexperienced designers (or ones working in large companies which already carry a diverse parts stock) into designing-in non-commodity parts.

A chip maker like say LT makes 10x more from one of those than somebody else makes from a 358.

Whereas if you are a designer working in your own business, you will do everything possible to avoid non commodity parts. That's what I have been doing since 1978 :)
Z80 Z180 Z280 Z8 S8 8031 8051 H8/300 H8/500 80x86 90S1200 32F417
 

Offline Zero999

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Re: Why is the 741 op amp still produced?
« Reply #61 on: September 23, 2020, 09:45:03 am »
However, if you ask someone at TI to recommend a simple low performance cheap op-amp they'll probably recommend an LMV321, or an LMV324 is you need several amps. Note than the LM321 is about as old as the 741, but most people use the more flexible LMV321 derivative these days. Nobody recommends a 741 any more, but a lot are still used in equipment whose design hasn't changed for decades.
How is the LMV321 more flexible, than the old LM321? It has some advantages: lower power consumption, bias currents and a rail-to-rail output, but the fact it only works up to 5.5V, rather than 30V, severely limits its applications, making it inflexible compared to the old LM321.
The supply voltage limitation hardly limits it at all in practice. In most modern designs people aren't looking to operate from 32V. They are looking to get great results from a 3V to 5V supply. The LM321 says it operates from 3V to 32V, but at 3V its performance is terrible. The LMV321 is described as rail-to-rail, which is always a bogus description, but it gets reasonably close. One of the things you have to watch out for with the LMV32x is that they are generic part, available from many suppliers, but some are closer to rail-to-rail than others. If you want flexibility in sourcing parts you need to ensure your design can work with the worst of them.
I don't get the obsession with using stupidly low voltages, for analogue. It increases noise and forces the use of more expensive, poorer performance components. More often than not, there's a >5V supply available to run the analogue section off, such as in an automotive application and there are still plenty of applications requiring >5V parts, such as high side current sensing. Granted, there are dedicated parts available to do this, but none so cheap as the old LM321 and a few resistors. Regarding 3V analogue, that's just silly and should only be done when there's no alternative. It's very rare there isn't a 5V supply to power an old LM321 off.
 

Offline coppice

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Re: Why is the 741 op amp still produced?
« Reply #62 on: September 23, 2020, 10:43:50 am »
I don't get the obsession with using stupidly low voltages, for analogue. It increases noise and forces the use of more expensive, poorer performance components. More often than not, there's a >5V supply available to run the analogue section off, such as in an automotive application and there are still plenty of applications requiring >5V parts, such as high side current sensing. Granted, there are dedicated parts available to do this, but none so cheap as the old LM321 and a few resistors. Regarding 3V analogue, that's just silly and should only be done when there's no alternative. It's very rare there isn't a 5V supply to power an old LM321 off.
These days the vast majority of analogue circuitry is a signal conditioning adjunct to digital circuitry, and people want to run both from the same rail. Even in applications like automotive, there are higher voltage available, but they will need regulating. If you can regulate just once for both the analogue signal conditioning and the MCU you have a win. 5V rails are becoming rare, as all new MCUs run at lower voltages than that. If you are building things like amps, then using high voltages is not just better, its essential. However, this is now a small part of the total market.
 

Offline Zero999

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Re: Why is the 741 op amp still produced?
« Reply #63 on: September 23, 2020, 12:49:13 pm »
I don't get the obsession with using stupidly low voltages, for analogue. It increases noise and forces the use of more expensive, poorer performance components. More often than not, there's a >5V supply available to run the analogue section off, such as in an automotive application and there are still plenty of applications requiring >5V parts, such as high side current sensing. Granted, there are dedicated parts available to do this, but none so cheap as the old LM321 and a few resistors. Regarding 3V analogue, that's just silly and should only be done when there's no alternative. It's very rare there isn't a 5V supply to power an old LM321 off.
These days the vast majority of analogue circuitry is a signal conditioning adjunct to digital circuitry, and people want to run both from the same rail. Even in applications like automotive, there are higher voltage available, but they will need regulating. If you can regulate just once for both the analogue signal conditioning and the MCU you have a win. 5V rails are becoming rare, as all new MCUs run at lower voltages than that. If you are building things like amps, then using high voltages is not just better, its essential. However, this is now a small part of the total market.
What are you talking about? 5V is pretty standard from USB/wall wart power supplies. True, it's often regulated down to 3.3V or whatever, but it's still available at the input.

Regarding automotive applications: that sounds like bad/lazy design to me. The LM321 can work from an unregulated power supply, so no it doesn't need to be regulated.  It just requires the usual anti-load dump transient protection, which you need anyway before the 5V/3V regulator. It can also tolerate its input voltages up to 32V, even when run from lower power supply voltages.
 

Offline coppice

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Re: Why is the 741 op amp still produced?
« Reply #64 on: September 23, 2020, 03:41:01 pm »
What are you talking about? 5V is pretty standard from USB/wall wart power supplies. True, it's often regulated down to 3.3V or whatever, but it's still available at the input.
What are you talking about? Most of the world's electronics doesn't run from a USB wall wart. 15 years ago many people complained when you offered them a part that could only work from 3V. If you were in a silicon vendor the sales people were endlessly asking for 5V tolerant parts from the designers. That has changed. Get with the times. Automotive seems to be the last bastion of 5V, but that is changing.

Regarding automotive applications: that sounds like bad/lazy design to me. The LM321 can work from an unregulated power supply, so no it doesn't need to be regulated.  It just requires the usual anti-load dump transient protection, which you need anyway before the 5V/3V regulator. It can also tolerate its input voltages up to 32V, even when run from lower power supply voltages.
Have you compared the price of an LM321 with an LMV321? Who wants to pay the price of a large geometry part that can tolerate high voltages, when most of your module is running from 3V or 5V anyway?
 

Offline Zero999

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Re: Why is the 741 op amp still produced?
« Reply #65 on: September 27, 2020, 10:33:03 am »
What are you talking about? 5V is pretty standard from USB/wall wart power supplies. True, it's often regulated down to 3.3V or whatever, but it's still available at the input.
What are you talking about? Most of the world's electronics doesn't run from a USB wall wart. 15 years ago many people complained when you offered them a part that could only work from 3V. If you were in a silicon vendor the sales people were endlessly asking for 5V tolerant parts from the designers. That has changed. Get with the times. Automotive seems to be the last bastion of 5V, but that is changing.

Regarding automotive applications: that sounds like bad/lazy design to me. The LM321 can work from an unregulated power supply, so no it doesn't need to be regulated.  It just requires the usual anti-load dump transient protection, which you need anyway before the 5V/3V regulator. It can also tolerate its input voltages up to 32V, even when run from lower power supply voltages.
Have you compared the price of an LM321 with an LMV321? Who wants to pay the price of a large geometry part that can tolerate high voltages, when most of your module is running from 3V or 5V anyway?
USB wall warts seem to be pretty universal.

The LM321 is cheaper than the LMV321. There clearly isn't any more debate to be had. If you've got 5V, or higher available, use that and the LM321, rather than 3V and the LMV321.
https://www.digikey.com/products/en/integrated-circuits-ics/linear-amplifiers-instrumentation-op-amps-buffer-amps/687?FV=-8%7C687&quantity=0&ColumnSort=1000011&page=1&k=LM321&pageSize=25&pkeyword=LM321
https://www.digikey.com/products/en/integrated-circuits-ics/linear-amplifiers-instrumentation-op-amps-buffer-amps/687?FV=-8%7C687&quantity=0&ColumnSort=1000011&page=1&k=LMV321&pageSize=25&pkeyword=LMV321
 

Offline coppice

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Offline Zero999

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Offline coppice

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Re: Why is the 741 op amp still produced?
« Reply #68 on: September 27, 2020, 02:48:14 pm »
The LM321 is cheaper than the LMV321. There clearly isn't any more debate to be had. If you've got 5V, or higher available, use that and the LM321, rather than 3V and the LMV321.
https://www.digikey.com/products/en/integrated-circuits-ics/linear-amplifiers-instrumentation-op-amps-buffer-amps/687?FV=-8%7C687&quantity=0&ColumnSort=1000011&page=1&k=LM321&pageSize=25&pkeyword=LM321
https://www.digikey.com/products/en/integrated-circuits-ics/linear-amplifiers-instrumentation-op-amps-buffer-amps/687?FV=-8%7C687&quantity=0&ColumnSort=1000011&page=1&k=LMV321&pageSize=25&pkeyword=LMV321
I find your use of Digikey as a measure of real prices hilarious.
The LM321 is also cheaper than the LMV321 in Mouser and RS Components.
Your point is? These are all places that serve low volume customers where prices bear little relation to volume prices. One part may be only 2 times the volume price, while others can be 100 times the volume price. Not only do these places not give you a clue about volume prices, they don't even give you a clue about relative prices.
 

Offline Kleinstein

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Re: Why is the 741 op amp still produced?
« Reply #69 on: September 27, 2020, 02:52:38 pm »
The LM321 are an odd product: quite a few of the LM321 versions seem to be actually LM358 dies using only one half: the supply current is usually the same as both OPs from the LM358 and not halve (or only slightly more)  :palm:. There seem to be a few now with lower current (e.g. from ONS).

For low voltage use (e.g. up to 5 V) there are quite a few affordable rail to rail CMOS OPs (e.g. MCP600x) - maybe not cheaper than the LM321, but below the 741.
One can also have a faster and less crossover distortion OP otherwise similar to the LM358 (e.g. MC33171-4) - this one could replace the 741 in most cases.
 

Offline Zero999

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Re: Why is the 741 op amp still produced?
« Reply #70 on: September 27, 2020, 04:22:02 pm »
The LM321 are an odd product: quite a few of the LM321 versions seem to be actually LM358 dies using only one half: the supply current is usually the same as both OPs from the LM358 and not halve (or only slightly more)  :palm:. There seem to be a few now with lower current (e.g. from ONS).

For low voltage use (e.g. up to 5 V) there are quite a few affordable rail to rail CMOS OPs (e.g. MCP600x) - maybe not cheaper than the LM321, but below the 741.
One can also have a faster and less crossover distortion OP otherwise similar to the LM358 (e.g. MC33171-4) - this one could replace the 741 in most cases.
I've never used the LM321, just the LM358. If I only want one amplifier, I just disable the other. The only reason for the LM321 is to save board space.
« Last Edit: September 28, 2020, 07:53:54 am by Zero999 »
 

Offline bson

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Re: Why is the 741 op amp still produced?
« Reply #71 on: September 27, 2020, 11:43:17 pm »
It's pretty much the only single-channel DIP-8 op amp that can handle a 44V supply.  Well, except the LF356 (JFET) and the LT1010.  Cheap as dirt, too (unlike the LT part).
 

Offline coppice

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Re: Why is the 741 op amp still produced?
« Reply #72 on: September 27, 2020, 11:57:57 pm »
It's pretty much the only single-channel DIP-8 op amp that can handle a 44V supply.  Well, except the LF356 (JFET) and the LT1010.  Cheap as dirt, too (unlike the LT part).
It will be interesting to see what happens to these higher voltage parts as less and less fabs remain functional which can produce them. People do not seem to see enough market size to justify developing new high voltage parts right now, although I guess they will be forced to as the last ancient fabs close. Some people will always need high voltage operation.
 

Offline james_s

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Re: Why is the 741 op amp still produced?
« Reply #73 on: September 28, 2020, 04:08:16 am »
It will be interesting to see what happens to these higher voltage parts as less and less fabs remain functional which can produce them. People do not seem to see enough market size to justify developing new high voltage parts right now, although I guess they will be forced to as the last ancient fabs close. Some people will always need high voltage operation.

What about fabs making HV parts like mosfet drivers, SMPS ICs and that sort of thing? Couldn't they make HV op amps? The market for things like motor drives and power supplies isn't going anywhere.
 

Offline Zero999

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Re: Why is the 741 op amp still produced?
« Reply #74 on: September 28, 2020, 07:53:43 am »
It's pretty much the only single-channel DIP-8 op amp that can handle a 44V supply.  Well, except the LF356 (JFET) and the LT1010.  Cheap as dirt, too (unlike the LT part).

Not all '741s are rated to 44V. The LM741C is only rated to 36V maxium.

The classic OP07 and NE5532 will withstand 44V, but are only specified to ±20V.

It will be interesting to see what happens to these higher voltage parts as less and less fabs remain functional which can produce them. People do not seem to see enough market size to justify developing new high voltage parts right now, although I guess they will be forced to as the last ancient fabs close. Some people will always need high voltage operation.

What about fabs making HV parts like mosfet drivers, SMPS ICs and that sort of thing? Couldn't they make HV op amps? The market for things like motor drives and power supplies isn't going anywhere.
Not to mention high side current sensing.
 


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