Simple enough question. Why not use a 741 op-amp in a target circuit or anyone's target circuit? What are the reasons not to use it? What might be the reasons to still choose this part?
Electronic – Reasons not to use a 741 op-amp
linearobsolescenceoperational-amplifier
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I agree with Oli:
If you have another chip, try that to make sure this one is not blown.
If they both do the same thing, then this smells like a case of phase-reversal. Op-amps have a valid common-mode input range. In the case of an LM741 (datasheet from www.national.com), the +/- 15V supply range yields a guaranteed +/- 12V common-mode input range. Outside that range, it used to be common for the output gain to sometimes reverse sign, causing positive feedback rather than negative feedback and the output to saturate at the rail until it came back into its valid input range.
Modern op-amps are carefully designed to not have this problem, because it's confusing and nasty to debug. Which is one of several reasons why my tongue-in-cheek comment ("basic 741 opamp answer: there's always a better op-amp to use") is good advice. There are plenty of cheap and good op-amps that have much better performance specs than the 741.
This webpage seems to indicate the 741 doesn't suffer from phase-reversal -- the ones that do are JFETS -- so maybe it is just your chip that's busted -- but I'd use the LM358 instead.
The datasheet gives an example.
By adjusting the pot we can null any offset error. An offset error is when the inputs are exactly equal but the output isn't exactly zero. This error is also characterized by the datasheet:
It can be safely ignored in AC applications, where this offset will be ignored by the AC coupling. It becomes more important in DC applications, especially amplifiers, since this DC error will be amplified by the next stage.
This offset voltage exists because a real omp-amp can't be ideal. There will always be some unintended asymmetries between due to random variation in manufacturing. In all cases, there are op-amp designs that can minimize these errors, but usually at the expense of some other parameter, like cost.
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Best Answer
There are many good reasons not to use the 1968-vintage LM741: -
The LM741A is slightly better but still a dinosaur in most areas.
Things of importance that the 741 data sheet does not appear to list (and that may depend on the age and manufacturer): -
I can't think of any valid reasons to use the 741 other than "that's all I will ever have or own". Common reasons why they are still used in actual devices appear to be: -
I've been an electronics designer since 1980 and I have never used or specified a 741 in any design I've been associated with. Maybe I'm missing out on something?