If they could do that they should to avoid offset error in first placeI was assuming offset voltage on inputs of a dual opamp would match. Wrong I guess?
That is a good observation. A dual op-amp with equal offsets could be arranged to eliminate the offset!If they could do that they should to avoid offset error in first place
It is possible. Here is a page of single and dual op-amps with 1 micro-volt of input offset voltage, in the range of $6.50. Whether that is practical depends on the circuit requirements.if practical to make offset predictable then practical to make offset exactly as wanted
FWIW: 'My money' says no! --- Nothing, but nothing is perfect and hence, "exact"!It is possible.
So... The LM358 'hit the market' on Sept 26 1971 (a Sunday?!) --- Aye! aye!! aye!!! -- I'll bet you play one mean game of Trivial Pursuit!The LM358 was an amazing feat of engineering in its day, but that was 16,000 days ago
It's perhaps obvious but that's for any output offset error due to the input bias currents. It has no significant effect on the output offset due to the input voltage offset.Opamp input error theory says that equalizing the DC impedances seen by the inputs will reduce the untrimmed offset error. Add a 10K resistor (9.53 K if you're picky) in series with each + input to see.
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OK, 16,000-ish.So... The LM358 'hit the market' on Sept 26 1971 (a Sunday?!)
I mean that if practical to make offset predictable then practical to make offset exactly as wanted
It's possible.
The blonde says, "exactly". The pragmatist says, "It's possible." but forgets to say, "to about 1 part per million", and the logophile objects. Entirely predictable.'My money' says no! --- Nothing, but nothing is exact!
More a (failed?) attempt at humor than pedanticism -- but what the hey! Its a fair cop!Then the logophile actually counts out 16,000.0 days on a calendar and the pragmatist thinks, "Academic is a nice word for pedant".
"Degenerate motion" is (or would be) an interesting, and, I daresay, even inspiring concept were it not for that "pesky' 'plank length issue' fairly ripping away the 'mist illusion' of purity -- Wadda worldI found this in the Jokes Thread. It seems appropriate.
A mathematician, a physicist, and an engineer were asked to review this mathematical problem. In a high school gym, all the girls in the class were lined up against one wall, and all the boys against the opposite wall. Then, every ten seconds, they walked toward each other until they were half the previous distance apart. The mathematician, physicist, and engineer were asked, “When will the girls and boys meet?”
The mathematician said, “Never.”
The physicist said, “In an infinite amount of time.”
The engineer said, “Well... in about two minutes, they'll be close enough for all practical purposes.”
Incredibly, I find the ('dirt cheap') LMC6482 to be possessed of remarkably consistent characteristics even lot-to-lot? --- Despite the prescribed protocol Re: 'gift horses', I am, nonetheless, keen to understand thisJust so much matching can be achieved with op amp design. Input transistors can be played with until they achieve good results or matching, but production variables always accumulate to ruin the performance. Precision op amps and instrumentation amps use active trim to achieve their excellent performance, and active trim costs time and silicon area (money). Anybody who uses LM358s expecting any degree of matching will be sorely disappointed. Adding a 10K resistor in the positive lead of the op amp reduces the bias current offset, not the voltage offset, and it introduces a small but real common mode voltage that can introduce other problems. Conclusion: buy the precision you desire and be willing to pay for it---written by an ex semiconductor company employee.
Thank you. You aren't the only person who makes, "jokes" that I don't understand. I will try to remember there are levels of humor that completely escape me the next time I feel an urge to mail a flaming paper bag to a certain person.More a (failed?) attempt at humor than pedanticism --
No problems! Someday maybe I'll embrace the sad fact that 'dry' humor and textual communication just don't 'mix' -- then again, maybe not...Thank you. You aren't the only person who makes, "jokes" that I don't understand. I will try to remember there are levels of humor that completely escape me the next time I feel an urge to mail a flaming paper bag to a certain person.
Even with this information, I fear it will take me some time to expand my horizons in that field of endeavor.