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Almost every op-amp tutorial I came across online goes in depth with their explanation on input offset voltage and input bias current (and input offset current). Not many I find discuss the null offset pin on the op-amp (or the input offset voltage adjustment range), or if not mentioned at all.

Take the old LM741 for example. Adding together the maximum input offset voltage of 5mV and 200nA input offset current (a mere 2mV for 10k source impedance) is still well within the null offset adjustment range of ±15mV. All I really need is just a good quality, accurate pot to balance the op-amp inputs. So long as the null offset pins is provided, I might as well ignore the offset voltage and current in the data-sheet - just tune the pot!

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    \$\begingroup\$ And if you had to make several thousand boards with many op-amps on them would you feed the same way? And if they tended to drift ...? And if you had to find space for the pots and make the accessible for service? And the cost of the pots? \$\endgroup\$
    – Transistor
    Oct 17 '20 at 14:27
  • \$\begingroup\$ a mere 2mV for 10k source impedance That might be good enough for you but I want < 1 mV from a 1 Mohm impedance, what makes you think that the 741's input offset is good enough for everyone else? Without context (show a circuit and explain its application) the "...should we care about..." is utterly meaningless. \$\endgroup\$ Oct 17 '20 at 14:43
  • \$\begingroup\$ @Transistor good points, though I was trying to question myself to confirm my understanding of the subject. So ... the null pin or the pot is used in development stage to get something up and working nice and quick, and later in production we devise a proper circuitry around the I/O to replace the pot for cost and stability reason? \$\endgroup\$
    – KMC
    Oct 17 '20 at 14:44
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    \$\begingroup\$ I don't think there is "a proper circuit". Each op-amp will have its own offsets so you can't just measure one and assume that all the others will be the same. The offset is an imperfection and one that should be avoided if possible. The uA741 was pretty bad. It's > 40 years old (and I used them back then) and has been superceded by several generations of op-amp technology. We only discuss them as bad examples nowadays. So, "... and later in production we devise a proper circuitry around the I/O to replace the pot for cost and stability reason?" No. We use a better op-amp. \$\endgroup\$
    – Transistor
    Oct 17 '20 at 14:51
  • \$\begingroup\$ @Bimpelrekkie that's not my question. I'm not trying to solve a problem. I'm still learning here at a conceptual stage. Why null pin exist? If it's not good enough to null out offsets at inputs, then it shouldn't exist in the first place and we should always come up with a proper circuitry to compensate these offsets. But they exist - hence the question. \$\endgroup\$
    – KMC
    Oct 17 '20 at 14:51
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Usually opamps with higher offsets also have higher temperature-dependent change in those offsets too. So you can still get undesirably-large offsets even with trimming.

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