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Related to What's the uA741's appeal?, a lot of schematics use this rather dated opamp. My follow-up question would be: What is a good alternative?

Of course if you have specific requirements you just search for the correct part. What I'm talking about is, what should be the default opamp I stock in my parts bin?

Imagine the average hobby project with a breadboard and an Arduino, single-supply, probably 5V, frequencies in the audio spectrum, and accidental shorts.

It should just be a nice, single-ended, well behaved (no phase reversal) opamp with a large voltage swing (preferably rail-to-rail), and reasonable performance for audio.

Some comments on the linked question mention LM358 and LM324, but I've read the low slew-rate may be bad for audio, which is what most of my analogue signals are.

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    \$\begingroup\$ Also worth a read: Reasons not to use a 741 op-amp? and personally I would say: anything else. Its not that the 741 has a better slew rate than those that you mentioned, does it? Anyways even for a hobbyist it should be important to learn how to chose a part that fits the purpose, and thus to learn about the paramters of opamps (or parts in general). There is no one part that will fit everything \$\endgroup\$ – PlasmaHH Jul 11 '17 at 8:28
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    \$\begingroup\$ Your requirements are already contradictory, which makes this a difficult question to answer. I would naturally assume that a replacement for an 741 should run well on +/-15 volt. Now you say you want low voltage and mix it with arduino. Then you're getting into specifics, not "generics". \$\endgroup\$ – pipe Jul 11 '17 at 8:29
  • \$\begingroup\$ I find the TL07x/TL08x tend to cover most basic needs. Not rail to rail, but then neither is the 741. \$\endgroup\$ – Ian Bland Jul 11 '17 at 12:18
  • \$\begingroup\$ I go with the MCP6004 because it's cheap, rail-t-rail I/O, unity gain stable, and works at 3.3-5V (but not much higher). The GBW product is high enough if you dn't have specific requirerments. Also comes in DIP. \$\endgroup\$ – DKNguyen May 6 at 13:50
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In complement to Andy's list of criteria, I'll add that most of the time, one of the usual suspects will do just fine.

For example:

  • MCP6002 is a good one. Dirt cheap (bag of 10 is 3€). It's your crummy CMOS opamp. It is slow so it won't oscillate on your breadboard, has Rail to Rail In/Out, the input common mode even extends a little bit beyond the rails. Low power too. Performance is nothing to write home about of course, but it is good enough for many uses.

Microchip makes opamps? Well, yeah. They have a whole line of CMOS opamps which do absolutely nothing spectacular besides being cheap, RRIO, low-power, low-voltage. These work on 3.3V and 5V so a good match for Arduino, Pi, etc. If you want faster, try MCP6292 (10MHz).

Good thing with these cheap crummy CMOS opamps is they work well on battery voltages, and they don't have the LM358 gotchas, like the input common mode going to GND but not VCC, or the output being "kinda able to go to 0V but only if it never has to sink any current" and the like.

Yeah, there are other $0.50 RRIO opamps which would fit the bill. Do I want to spend 2 hours selecting a 50c opamp for a hobby project when I know this one will work? Probably not...

Also, cost. For amateur, hobby stuff, you gonna spend hours laying out that board, so when performance is needed, it's not worth it to skimp on the parts! Get a $3 opamp if it saves you a headache, it's well invested...

For example, if you want to filter and buffer a DAC or a PWM from an arduino and get a 0-5V output, there's no excuse for using an opamp which needs a negative supply voltage when you got 30c RRIO opamps which will do the job with only a 5V supply!

Audio, for example: if you need cheap, NE5532. If you need high quality, OPA1642, OPA1652, LME49720 and others in the same families are very good.

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  • \$\begingroup\$ Microchip also sells the 6V01 autoZero opamp, with +-1uV offset. \$\endgroup\$ – analogsystemsrf Jul 11 '17 at 13:45
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    \$\begingroup\$ Thank you for providing a solution instead of a list of more problems. Definitely ordering a bag of MCP6002 on my next order, and sample some of the audio ones for later. Fun fact: Yesterday I ran into the not-really-zero-under-load issue with the LM358. \$\endgroup\$ – Pepijn Jul 13 '17 at 6:46
  • \$\begingroup\$ @Pepijn the devil is in the detail - look at and understand figure 2-14 of the data sheet for the MCP6002. Output current magnitude also includes current down the feedback path so be careful in believing this part might be superior to the LM358 on low voltage outputs. Typical figures indicate the 358 is at least twice as good as the 6002. That is why my answer lists problems so that those that are learning understand the pitfalls. \$\endgroup\$ – Andy aka Jul 17 '17 at 10:18
  • \$\begingroup\$ Yeah, it's a CMOS opamp, so no current noise, low value feedback resistors are not useful here... Same if you want low power! \$\endgroup\$ – peufeu Jul 17 '17 at 10:44
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what should be the default opamp I stock in my parts bin?

It's a failure on your part to think that there is a default op-amp that suits most applications. It's as simple as that. It's also a failure to limit what you think are the important parameters to those that you have stated.

There are many important parameters that may be important to a particular target application but, these parameters may be of no-consequence to a different application.

Examples are, but not limited to: -

  • Input offset voltage
  • Input offset voltage drift with temperature
  • Input bias and offset currents
  • Input common mode range
  • Input impedance (resistance and capacitance)
  • PSRR
  • CMRR
  • Phase margin
  • Input equivalent voltage and current noises
  • Ability to operate down to 1.8 volts on power supply
  • Operating current
  • Output impedance versus frequency
  • Open loop gain

Your question is asking about the uA741 yet you quote a general application that would run on 5 volts - are you aware that the minimum recommended power supply is sometimes as high +/-10 volts with some hints in some data sheets that +/- 5 volts will be OK.

The ST uA741 is quoted to run at 5 volts but this is the exception rather than the rule.

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    \$\begingroup\$ +1 for the gigantic list of things to consider. OP, instead of trying to have a single "default" op-amp, considering having a selection: it's not possible to select an op-amp that is appropriate for every project. \$\endgroup\$ – uint128_t Jul 11 '17 at 14:58
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    \$\begingroup\$ I really understand the OP. It is nice to have some OpAmps laying around; to be prepared when you want to start a new project instead of waiting days/weeks/months (ebay do you hear me?) for them to arrive. And unless you do extraordinary things, most general-purpose OAs will fit your needs. So instead of buying a bug of 741 why not buying the better/newer alternatives. \$\endgroup\$ – WeGoToMars May 6 at 12:46
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Ne5532 is a good all purpose opamp. Tda1308 is another one for good low voltage application. It has poorer DC performance however.

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Because you mentioned Arduino (low power, low voltage):

LM358N - 0.5mA, min 3V 1MHz
MCP6001 - 0.1mA, min 1.8V 1MHz
LM324 - 0.7mA, min 3V 1MHz (quadruple)
NE5532a - ?mA min +-5V (10MHz!)
TDA1308 - 3mA, min 3V, (class-AB stereo headphone driver, circ boards already available on ebay for $1)
LM193, LM293, LM393, LM2903, min 2V

Note:
* min is minimum voltage required to run
* mA is typical current consumption
* I am going to prepare a RAR file with the data sheets for all the above ICs and upload it somewhere (for lazy people like me).

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Here is a brief answer - go to a distributor site and look at the op-amp section. One can normally select by parameters. For example, Farnell

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  • \$\begingroup\$ "Of course if you have specific requirements you just search for the correct part. What I'm talking about is, what should be the default opamp I stock in my parts bin?" \$\endgroup\$ – pipe Jul 11 '17 at 11:03
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    \$\begingroup\$ @pipe No, you look up the parameters of the 741 and then use the table to find something better \$\endgroup\$ – Dirk Bruere Jul 11 '17 at 11:09

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