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Bit of history. I made a simple electronics design which needed (in this specific case) an input follower. I then did some simulation with some online simulation tools (not in LTSpice at the time, which was apparently a mistake) and decided to go for it. Next, I browsed through quite a few tutorials and datasheets, and eventually decided to go for a NE5532 opamp.

As it turns out, the NE5532 was totally unsuitable for my needs. I needed the input follower to handle voltages of roughly 0-2.5v powered by 5v and when I put the design in LTSpice and added a sine wave, I immediately saw that it doesn't work at all. So, I replaced the opamp with an LM358 which i had lying around and all my issues vanished into thin air. Great.

However, for me the question now becomes: how can I learn from this, so that I won't repeat my mistake? So I went back to both datasheets and attempt to determine where it went wrong. And frankly, I'm at a bit of a loss here... the reality is that if I were to pick an opamp again, I'd probably do it wrong again.

So my question here is: how can I determine what's a suitable opamp from the datasheet for different needs?

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    \$\begingroup\$ Some time ago I answered a question on why there are just so many different types of opamp. I did not go into some of the issues you raise here but you may find it useful as an addition to the excellent points below. electronics.stackexchange.com/questions/189823/… Some links may not work - I will update it in a few days. \$\endgroup\$ Oct 11, 2023 at 16:04
  • \$\begingroup\$ Thanks for the addition. I'm still attempting to chew down all the information here. \$\endgroup\$
    – atlaste
    Oct 11, 2023 at 17:44

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Here is what I check: -

  • That the minimum recommended power supply rails are within your actual power rails

  • That the maximum recommended power supply rails are greater than your actual power rails in the worst case scenario

  • Input voltage range is typically from -Vs + 2 volt to +Vs - 2 volt for many op-amps but, modern ones can be much, much better

  • Input offset voltage is typically 1 mV for many op-amps and this creates a DC error for many circuits that can't be tolerated. Modern op-amps can be much, much better than this.

  • Input offset voltage drift (vs temperature) may also be important to consider

  • Input offset current is typically 20 nA (200 nA maximum) for many low-grade op-amps and, this will cause a DC error. If that's important to minimize then, modern op-amps are commonly available that are less than 100 pA

  • Input bias current is typically 80 nA (500 nA maximum) for cheap shoddy op-amps but, many modern op-amps are commonly less than 1 nA

  • Input resistance is typically 2 MΩ (300 kΩ minimum) for something like a 741 (a proper PoS) and this can be cruel to op-amp filter circuits so, if that is important in your design, take note that many modern op-amps have input resistances that start at hundreds of MΩ

  • Typical output voltage swing is -Vs + 1 volt to +Vs - 1 volt for cheap old op-amps and this may not be a problem on many designs but, if it is, then take note that many cheap rail-to-rail op-amps get their outputs to within a few mV of the supplies.

  • Typical output voltage swings may mask that fact that guaranteed output voltage swings of -Vs + 3 volt to +Vs - 3 volt may be present.

  • Supply current is typically a few mA for most older common op-amps so, if running from batteries, check the data sheet. Modern op-amps (with this level of current consumption) are usually ten times faster and better in many other ways too.

  • Equivalent input noise is 60 nV/sqrt(Hz) for an ancient device like the LM348 (quad version of 741) and, again, if this could create problems, pick a device that is seriously better.

  • GBWP is 1 MHz with a slew rate of 0.5 V/us for a lot of old cheap op-amps and this just doesn't cut-the-mustard in many designs.

See also Reasons not to use a 741 op-amp

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  • \$\begingroup\$ Right, so basically what you say is "if the voltage ranges are good and you don't optimize on pennies, consider buying a newer opamp as a starting point". Fair enough. I'm guessing that it's possible to select that based on the date & revision in the copyright notice in the datasheet as well? :) \$\endgroup\$
    – atlaste
    Oct 11, 2023 at 18:08
  • \$\begingroup\$ I'm saying exactly what is detailed in my answer @atlaste and, unfortunately, I didn't understand what you were guessing. \$\endgroup\$
    – Andy aka
    Oct 11, 2023 at 18:14
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In this case, the problem was that a 5532 output is designed to operate from balanced supplies of typically +/-15V or so, and the output is only guaranteed to swing to within one or two volts of the supplies.

Obviously this won't work with a single 5V supply.

In general you need to consider the application and derive some requirements from that. Typically:

  • recommended supply voltage
  • ability to drive a load
  • bandwidth (or gain-bandwidth product)
  • output swing (into what load?)
  • DC offset currents and voltages
  • distortion and noise

but which of these really are important depends entirely on the application. A thorough revision of the important op amp parameters and configurations would be very helpful here.

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