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Since it doesn't matter for the Op. Amp. itself, the components presented as "single-supply" commonly relate to rail-to-rail input/output devices, which operate on lower total voltage supplies. If the input and output signals and their DC offsets operate within the limits, everything works fine regardless of the power supply (single or dual).

Since they are equivalent, "total" operating voltages are normally the same:

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But in this INA datasheet, different values are presented:

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At the page 20 of the datasheet there are detailed informations on input voltage range, including the Vref pin, but I could not relate this with the asymmetry in supported supply voltages. The difference is even higher for the AD8227.

If the reason for the different lower operating power supply voltages was a reliable Vref, it would be harder to use the INA with single-supply, and not the other way around.

Question: any idea on why can't this device work with ±1.1V?

References:

AD822 Datasheet

AD8226 Datasheet

AD8227 Datasheet

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2 Answers 2

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The front page of the datasheet is marketing information, not engineering. The reason for the specs being this way is most likely that somebody in the marketing department thought that there were customers who want +2.2 V operation, and customers who want +/- 1.35 V operation, but didn't think there were a significant number of customers who want +/- 1.1 V operation.

If you look in the Characteristics tables, you'll see that there are no specifications for the behavior of the part with a +2.2 V supply. Only for +/- 15 V and + 2.7 V.

If you're building 1 or 10 or 100 of a circuit, you might try operating it at 2.2 or +/- 1.1 V, and it's possible it will work. It's also possible it won't work, because they specify the part with Vref at 0 V, and it might not work with Vref only 1.1 V below the positive supply.

If you're building 1,000,000 circuits, you probably want to stick to operating the part according to the conditions in the Characteristics table.

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  • \$\begingroup\$ Thanks, yes. Sometimes this is clear even in the front page. E. g. for the TLV232x datasheet: "Fully Characterized at 3 V and 5 V" and "Wide Range of Supply Voltages [...] 2 V to 8 V". And even "Each amplifier is fully functional down to a minimum supply voltage of 2 V, is fully characterized, tested, and specified at both 3-V and 5-V power supplies.". \$\endgroup\$
    – devnull
    Commented Mar 2, 2021 at 17:07
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You could use +/-1.1V for supply but Vin+ max = +Vs − 0.9 = 200mV, then a suitable buffer Vref is needed. So since it asymmetric for biasing reasons , can you live with this limitation?

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  • \$\begingroup\$ Yes. Its sad that even for 2.7V operation @ fixed 25C the distance from input to +Vs can't be smaller than 0.7V (assuming the worst case). \$\endgroup\$
    – devnull
    Commented Mar 2, 2021 at 17:33
  • \$\begingroup\$ It might be ok for high gain then the input is kept low using the inverting input. Or perhaps differential configuration. \$\endgroup\$ Commented Mar 2, 2021 at 17:39

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