Extraction: Inductance

The inductance of conductors as well as the inductive coupling factor between conductors can be caluculated. The calculation is three dimensional. The height value of the shapes is set in the LayerManager for each layer. The layer level, layer thickness and 2d shape define the three dimensional shape for each contuctor (see also ExtractionCapacitance and 3dView). It is not only the conductor shape that is required to calculate inductance , the direction of current flow within any conductor is also required. The current flow is defined by the kind of the shape. In paths, a current flow is assumed along the path length and parallel to the drawing surface. In boxes and polygons the current flow is assumed perpendicular to the drawing surface. For the example below, in coil1 the two coil layers had to be drawn as paths and in contact with the middle as box or polygon. The inductance calculation is done by the external calculation tool FastHenry. FastHenry is included in the LayoutEditor package and triggered by the calculation button in the dialog.


  • Open extraction tools (Utilities/Misc/Electrical Extraction)
  • select shapes for the first conductor
  • press addConductor to add the selected shapes as a conductor
  • repeat these steps for any conductor
  • start the calculation


The FastHenry algorithm is used for the calculations. FastCap and FastHenry, from MIT (Massachusetts Institute of Technology) are two free parasitic extractor tools for capacitance, and inductance and resistance. Quoted in many scientific articles, they are considered golden references in their field. It is a three dimensional calculation. FastHenry is included as a compiled stand alone version in any LayoutEditor package and it can be used separate from the LayoutEditor by manual call.