Why Signal Source definition is mandatory?

  • I have not understood why I have always to select a signal source when I perform a Transient simulation.
    If I leave "none" when I create the simulation it returns an error: "No source component has been selected."
    Normally I declare the voltage/current sources in the schematic and that's all, What is wrong?
    I supposed the reason to do that is to have control in GUI of the signal source but, in case, it seems a bit strong the choice to oblige a signal source definition; it is also a limitation because not all signal source can be defined with setup options. I suggest to remove the error created by no signal source definition.

    Another point related to this problem:
    I have performed a very simple simulation with both ng-spice e gnu-cap.
    With different results: ng-spice is correct but GNU-cap is not correct.
    The problem is related to the signal source definition in GNU-cap. I have a sinusoid with 2.5V of offset but the first point of simulation is set to zero instead of 2.5V; this cause an unwanted step between the first two point. This step is not present if I remove the GENERATOR defined by the GUI.

    Thank a lot for the nice software I hope I will help you testing it
    Otherwise sorry for the time consuming questions


    • I found the source of the error. In the signal source definition it is impossible to set the initial value for sinusoid. So if you have a nonzero offset (or nonzero start degree) the generator start with its default value (zero). If you modify the GENERATOR definition adding "INITIAL=2.50" it will works.


    • Mike W.
      Mike W.

      Thanks for the feedback.