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what is the meaning of iprobe component in analogLib?

Gordon1002

recently, I want to measure a basic opamp in virtuoso. My classmates suggest me use the iprobe component to measure it. I read the describetion about iprobe in Spectre document. It says"Current through the probe is computed and is defined to be positive if it flows from the input node, through the probe, to the output node. The current variable is given the name of the iprobe instance, so you cannot create an iprobe with the same name as a circuit node." So why I can't just use ADE-L tool and select the component's node to measure the current? What is the difference of these two method? It bother me a lot , Thanks!

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  • Frank Wiedmann

    I believe that Spectre treats the iprobe like a voltage source with 0 V. In Modified Nodal Analysis, currents through voltage sources appear as unknowns and are explicitly solved for (unlike most other currents), which might give more precise results for these currents.

  • ShawnLogan
    in reply to Frank Wiedmann

    Dear Gordon1002,

    Gordon1002 said:
    So why I can't just use ADE-L tool and select the component's node to measure the current?

    I may not be understanding your question, but the reason you cannot simply select either of the two circuit nodes to which the probe instance is connected is that is a circuit node and hence will represent a voltage. You are interested in the current through that net and hence you must choose not the net itself, but the input or output terminal of the iprobe instance. If you want to save a current through any terminal of a subcircuit, you can choose its terminal. Virtuoso differentiates a signal voltage that is saved from a current by highlighting the entire circuit node for a voltage signal and by a round circle surrounding the terminal of a symbol for a current.

    Did I understand your question and does this make sense Gordon1002?

    Shawn

Reply
  • ShawnLogan
    in reply to Frank Wiedmann

    Dear Gordon1002,

    Gordon1002 said:
    So why I can't just use ADE-L tool and select the component's node to measure the current?

    I may not be understanding your question, but the reason you cannot simply select either of the two circuit nodes to which the probe instance is connected is that is a circuit node and hence will represent a voltage. You are interested in the current through that net and hence you must choose not the net itself, but the input or output terminal of the iprobe instance. If you want to save a current through any terminal of a subcircuit, you can choose its terminal. Virtuoso differentiates a signal voltage that is saved from a current by highlighting the entire circuit node for a voltage signal and by a round circle surrounding the terminal of a symbol for a current.

    Did I understand your question and does this make sense Gordon1002?

    Shawn

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