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Problem with ADA4940 LTspice model

Category: Software
Product Number: ADA4940
Software Version: LTspice (x64) 17.1.10

Hi, 

I discovered strange behavior from either the ADA4940 model or the LTspice itself. The second assumption seems more accurate.

As you can see in the screenshots above, splitting the gain resistor changes the gain settings of the circuit.

Is this a know issue? And if so, what is the solution/workaround?

  

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    •  Analog Employees 
    •  Super User 
    in reply to EZAutoReply +1 verified

    Hi ,

    Good day. I think the way you set the values of the resistor was the main reason why there is a discrepancy between the expected and the simulated gain response. The resistor value should…

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  • Hi ,

    Good day. I think the way you set the values of the resistor was the main reason why there is a discrepancy between the expected and the simulated gain response. The resistor value should directly be input as a numeric value with the proper prefix if necessary. There should be no difference in the simulations since the resistor model used in LTSpice was ideal.

    I have tried to simulate the circuit.  The simulations below show no difference in the gain response even if the resistor was split into multiple values.

    Fig 1. Schematic Diagram with a Single Gain Resistor

    Fig. 2. Gain Response of a Single Gain Resistor

    Fig 3. Schematic Diagram with Splitted Gain Resistor

    Fig 4. Gain Response of Splitted Gain Resistor

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  • Hi ,

    Good day. I think the way you set the values of the resistor was the main reason why there is a discrepancy between the expected and the simulated gain response. The resistor value should directly be input as a numeric value with the proper prefix if necessary. There should be no difference in the simulations since the resistor model used in LTSpice was ideal.

    I have tried to simulate the circuit.  The simulations below show no difference in the gain response even if the resistor was split into multiple values.

    Fig 1. Schematic Diagram with a Single Gain Resistor

    Fig. 2. Gain Response of a Single Gain Resistor

    Fig 3. Schematic Diagram with Splitted Gain Resistor

    Fig 4. Gain Response of Splitted Gain Resistor

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