To set up an AC analysis, the frequency range must be specified and AC-specific parameters for voltage and power sources be set. For signals, the desired component to display must be specified.

Before you begin​

Set up the simulation as described in

Setting up a simulation

, but do not specify any signals yet.

About this task​

Set up an AC analysis when you want to analyze the frequency response of a device.

Procedure​

  1. Double-click the voltage source of the schematic.

    The

    Properties

    dialog opens.

  2. Set the ACM parameter and, if desired, the ACP parameter.

    ACM

    The AC magnitude (acmag). When performing AC analyses, this parameter is used instead of the standard VA setting of the voltage source.

    ACP

    The AC phase (acphase). An optional setting specifying the starting phase of the voltage source's output.

  3. Repeat these steps for any other voltage and current sources.

  4. In the

    Analyses

    tab of the

    Simulation Environment

    view, check

    AC

    if it not already checked.



    You can check additional analyses (such as OP or DC). If you do so, an additional Waveform Viewer window will open for each analysis when the simulation is run.

  5. Specify the sweep range for the frequency.

    Set the desired type of sweep: log based on decades, log based on octaves, or linear. This determines the distribution of the points.

    Set the number of points. The simulation will be performed at each point. For logarithmic ranges, each decade or octave section has the specified number of points. For linear ranges, the number of points is distributed across the entire sweep range.

    Set the desired start and end frequencies.

  6. In the

    Plot Setup

    tab, specify the desired signals in the

    Signals

    section.



    1. Check the AC Modifier option.

    2. Specify the desired component that you want to graph: magnitude, attenuation (db20), phase, real component, or imaginary component.

      This setting affects just the initial display in the Waveform Viewer. You can add the other modifiers as separate traces without having to rerun the simulation.

      Note that the real and imaginary components of the named voltages and currents of the schematic are automatically added to the analysis and do not need to be specified as signals. However, other aspects of these values, such as attenuation or phase, are not automatically added. If you want to have them included in the initial plot, you must add them as signals. Alternatively, you can add them when reviewing the simulation results, as described in

      Evaluating AC analyses

      .

    3. Click the appropriate selection tool in the upper left corner of the section and use it to select the desired signal in the schematic that you want to include in the simulation.

      The signal is added to the signal list.

    4. In the

      Analysis

      column of the newly added signal, choose

      AC

      .

    5. Repeat these steps for any other signals you want to add to the analysis.

Results​

The AC analysis is now set up and you can run the simulation as described in Running a simulation. For evaluating the simulation results, everything in applies. Specific considerations for AC analyses are described in Evaluating AC analyses.