chopper stablized amp explain

Discussion in 'General Electronics Chat' started by bug13, Sep 25, 2013.

  1. bug13

    Thread Starter Well-Known Member

    Feb 13, 2012
    1,208
    38
    Hi guys

    I am reading a tutorial from ADI here about copper stabilized amp. on page 2, figure 2, I can understand how to null the Vos of the nulling amplifier (A2) when the two switches are at Z(zero) position.

    But I don't understand how the nulling amplifier (A2) null out the Vos of the main amplifier(A1) at position S(sample), I mean the the input is always connected to the main amplifier (A1), how does the nulling amplifier (A2) measure the main amplifer(A1)'s Vos and put it in C2?

    Thanks guys!
     
  2. crutschow

    Expert

    Mar 14, 2008
    13,053
    3,244
    The input to A2 measures the differential input voltage of A1. If the loop around A1 is closed (as would normally be the case) then this differential voltage corresponds to the offset of A1, independent of any signal voltage. Thus A2 can correct for the offset voltage of A1.

    That make sense?
     
  3. bug13

    Thread Starter Well-Known Member

    Feb 13, 2012
    1,208
    38
    Arrhh... yes it all make sense now, why didn't I think of it, thanks a lot!
     
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