ADA4857 SPICE Simulation Output Impedance

I am running a SPICE simulation (in Altium Designer) using the supplied model for the ADA4857.  If I load the output of the amplifier with anything less than 1Meg or so the output sags very significantly - but I get reasonable performance with a 1Meg load.  In the data sheet it mentions performance into a 1K load.  I am down 20dB when I drive a 1K load.  I have checked and double checked my connections and everything looks correct.  Suggestions of what might be wrong or how to go about troubleshooting this issue would be most welcome. Thanks!

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  • Here is the pertinent connection info:

    From the model

    *Node Assignments
    * Non-Inverting Input
    * | Inverting Input
    * | | Positive supply
    * | | | Negative supply
    * | | | | Output
    * | | | | | FB
    * | | | | | | PD
    * | | | | | | |
    .Subckt ADA4857 100 101 102 103 104 105 106

    From the netlist

    XU1 P_IN N_IN PLUS5 MINUS5 VOUT N_IN GND ADA4857

Reply
  • Here is the pertinent connection info:

    From the model

    *Node Assignments
    * Non-Inverting Input
    * | Inverting Input
    * | | Positive supply
    * | | | Negative supply
    * | | | | Output
    * | | | | | FB
    * | | | | | | PD
    * | | | | | | |
    .Subckt ADA4857 100 101 102 103 104 105 106

    From the netlist

    XU1 P_IN N_IN PLUS5 MINUS5 VOUT N_IN GND ADA4857

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