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OPA2376: Does OPA2376 offset voltage become bigger than typical offset voltage spec when input pin (+IN,-IN)voltage is very low?

Kazuya Nakai59
Guru 20130 points
Part Number: OPA2376

Hello guys,

One of my customers is evaluating OPA2376 with low pass filter circuit like the follow.(But +IN=+100mV, V+=+5V, V-=0V)

https://www.avrfreaks.net/forum/why-simple-op-amp-low-pass-filter-does-not-work

The customer parameters are the follow.
R1 = 1k ohm.
R2 = 68k ohm
C = 0.01uF

They found that OPA 2376 offset became about 150uV when Vin in the circuit above is about +50mV.
Is this normal phenomenon of OPA2376 when input pin (+IN,-IN)voltage is very low?

We found Offset and Common-Mode Voltage graph on page 15 of OPA2376 datasheet.
According to the graph, the device offset voltage is bigger than the offset spec (5uV(Typ)) when input pin (+IN, -IN) voltage is very low.

Your reply would be much appreciated.

Best regards,

Kazuya.

  • 0
    Guru 140200 points

    Hi Kazuya,

    I think you mean figure 23 of datasheet?

    The offset voltage specified in the datasheet in section 6.7 is only valid for a certain common mode input voltage, which is mid-supply here. See the conditions given in the header. Outside this condition the input offset voltage can vary.

    Kai

  • 0 in reply to kai klaas69
    Guru 20130 points

    Hello Kai,

    Thank you very much for your reply.

    Yes, I mean figure 23 of datasheet.
    I understood what you said.

    So do you think 150uV offset voltage is reasonable?

    Could you please give you any comment?

    Thank you again and best regards,

    Kazuya.

  • 0 in reply to Kazuya Nakai59
    TI__Guru 60610 points

    Hi Kazuya,

    Yes, at Vcm=(V-)+50mV, the OPA2376 input offset voltage may be at 150uV at 25C but it may get even worse at elevated temperature for as long as the Vcm<(V-)+0.2V