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LM321: If pulling high a resistor to V+ at +IN port, can it offset input offset voltage?

Alex Chen
Prodigy 40 points
Part Number: LM321
Other Parts Discussed in Thread: TLV07, OPA189, OPA991

Hi there,

In the datasheet of LM321, the input offset voltage is 2mV typically. Does it mean +IN needs to be 2mV higher than -IN? Or it is possible that -IN needs 2mV higher than +IN? So the extended question is pulling high at +IN right or wrong?

Regards

Alex Chen

  • 0
    Guru 269830 points

    This can go in both directions. And typical values are not guaranteed; the offset voltage might be up to ±7 mV, so in a circuit with negative feedback, +IN might be up to 7 mV higher or lower than −IN.

    In general, a resistor cannot create a fixed offset voltage, so you would need a more complex circuit, and you would have to calibrate each board. Better use an opamp with a lower offset voltage, e.g., TLV07, OPA991, or OPA189.