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OPA828: OPA828 Figure 6-26 errors

Michael Steffes
Guru 48395 points
Part Number: OPA828

Kind of scanning through the OPA828 datasheet (2022 update) this plot 

So that Aol over temp plot should say 1/Aol and I really doubt it flips polarity over temp 

  • 0
    Guru 48395 points

    That 1/Aol going negative is basically saying the Aol phase is flipping around 180deg which should produce an oscillator going cold - probably really does not do that and this plot is getting mired with measurement noise. 

  • 0 in reply to Michael Steffes
    TI__Guru 63900 points

    Michael,

    You are correct - since zero-crossing around 55 deg C in AOL vs Temp graph would implied infinite AOL, the negative numbers should have been taken absolute values of for the purpose of generating the graph.  Thus, the actual graph may look more like the one shown below:

  • +1 in reply to Marek Lis
    Guru 48395 points

    ABS value? really it is just your input err signal is lost in the noise not inverting polarity. Your redrawn suggest the Aol is going way up going cold, really? Not that important of a graph, but just misleadiong right now. 

  • 0 in reply to Michael Steffes
    TI__Guru 63900 points

    Assuming that he noise had been completely filtered out, the zero-crossing in AOL vs Temp graph implies some DC error that has NOT been calibrated out.  As far as according to my redrawn graph AOL getting highest at cold, the graph is just a typical curve that may significantly vary from unit to unit.