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Datasheet Notification Missing

GARAM AN
Intellectual 2010 points
Other Parts Discussed in Thread: OPA837

Hello,

Sometimes there are full written in the MIN TYP MAX, but sometimes one of them is missed like below table.

Why is this missed in the datasheet?

Parameter MIN TYP MAX
Vos Input Voltage Offset +-0.3 +-1.6

  • 0
    Guru 48395 points

    Well certain kinds of specs are implicitly a 0 min and do not need to be specified. 

    The input offset voltage is an interesting one, this usually has a nice gaussian centered on zero distribution - so physically the typical is 0uV. But that does not make it very easy to compare parts, so the practice started with the original BurrBrown precision op amps to use the 1sigma value as the typical +/- input offset voltage (will encompass 63% of the population). the max. then is normally 4 to 5 sigma and is often screened in final ATE - usually +/- 4 to 5sig spread.  

    You did not give a part number but for instance we put this plot into the precision OPA837 device, this one is trimmed at wafer level to near 0uV but packaging stress induces a final spread - slightly offset positive here

    Compare this to the specifications, and again, that +/-30uV is 1sig while the +/-165uV is wider than the plotted histogram (but still about +/-5sig limits) - often that wider spread in the spec limits vs plots is including poor temperature control at ATE and required repeatability guardband across multiple boards and testers. 

  • 0 in reply to Michael Steffes
    TI__Intellectual 2010 points

    On the OPA873 datasheet, we can see the maximum value of Aop(Open-loop voltage gain) is missing. Could you explain what this is meaning?

  • 0 in reply to GARAM AN
    Guru 48395 points

    Since this is an ATE spec (the A in the right column, a template I developed for the BurrBrown HSP parts), it cannot be resolved accurately - and, since higher is better who needs to know? So the typ is is maybe designer simulations, while the min is probably set more by test repeatability. Think about what that measurement is, for a+/-2V output, at a 120dB min limit that is an input error voltage swing of 4/1e6 = 4uV. Yea, you can resolve lower with averaging, but there are test time limits as well.