General > General Technical Chat
Why is the 741 op amp still produced?
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peter-h:
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 :)
Zero999:

--- Quote from: coppice on September 22, 2020, 10:14:08 am ---
--- Quote from: Zero999 on September 22, 2020, 09:58:59 am ---
--- Quote from: coppice on September 21, 2020, 10:00:41 pm --- 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.

--- End quote ---
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.

--- End quote ---
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.

--- End quote ---
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.
coppice:

--- Quote from: Zero999 on September 23, 2020, 09:45:03 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.

--- End quote ---
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.
Zero999:

--- Quote from: coppice on September 23, 2020, 10:43:50 am ---
--- Quote from: Zero999 on September 23, 2020, 09:45:03 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.

--- End quote ---
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.

--- End quote ---
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.
coppice:

--- Quote from: Zero999 on September 23, 2020, 12:49:13 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.

--- End quote ---
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.


--- Quote from: Zero999 on September 23, 2020, 12:49:13 pm ---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.

--- End quote ---
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?
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