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OPA2197: Offset voltage drift spec near V+ rail

Taketo Sato
Genius 10355 points
Part Number: OPA2197


Hello team,

How can I think about offset voltage drift in near V+ rail condition?

Datasheet shows offset voltage drift specification with Vcm=(V+)-1.5V as test condition. At same time, OPA2197 Vcm range reaches to V+ rail.

Does offset drift get worse if Vcm is larger than (V+)-1.5V, or remain same?

I think Vcm=(V+)-1.5V condition represents NMOS input operation area, and we can reference the spec for also when Vcm is larger than (V+)-1.5V, correct?

Best regards,

  • 0
    TI__Guru* 93105 points

    Sato-san,

    You are correct, the OPA2197 N-channel input differential stage is in operation once the input common-mode voltage (Vcm) gets to within about 2.5 to 2 V of the positive supply rail.

    All we specify for the OPA2197 drift is what is stated in the OPA2197 Electrical Characteristics table. Therefore, because the table does not specify the drift exactly at Vcm = V+ we cannot state a drift limit for that condition. However, I have reviewed the original characterization data for the OPA219x family and I can tell you that nothing extraordinary occurs in the positive Vcm region from (V+) - 1.5 V to V+. The slope remains about the same as it is at (V+) - 1.5 V and will have similar drift (dVos/dT) to what is listed in the table.

    Regards, Thomas

    Precision Amplifiers Applications Engineering

  • 0 in reply to Thomas Kuehl
    TI__Genius 10355 points
    Hello Thomas-san,

    Thank you for your comments.
    Datasheet doesn't specify drift performance with Vcm=V+ test condition, so TI cannot guarantee but we can think 4.5uV/C as max value also Vcm=V+ condition, correct?
    If above is wrong and drift performance will slightly get worse in very near V+ input, how much margin should be reasonable for the drift performance? 10% margin should be reasonable?

    Best regards,
  • 0 in reply to Taketo Sato
    TI__Guru* 93105 points

    Hello Sato-san,

    We cannot assure that the Vcm = V+ drift will be 4.5 V/°C maximum because the datasheet does not state that. What we can say is that the highest drift at Vcm = V+ will be approximately 4.5 V/°C, but it could be higher for some OPA2197 devices

    Regards, Thomas

    Precision Amplifiers Applications Engineering