I am reading this link about ferrite beads and in page 2, figure 2, there is a SPICE circuit to emulate the ferrite beads frequency response.

Why there is an AC Current Source in the circuit? Why just dont "plug" the bead to the AC Voltage sorce and Ground and run the simulation?


With a 1 ampere AC current source in series with the ferrite bead model, the voltage across the ferrite bead at its terminals (including all of the R's, L', and C's) is numerically equal to it's impedance. Thus plotting that voltage against frequency gives the desired result of ferrite bead impedance vs. frequency which are the plots given in the application note.

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  • \$\begingroup\$ Why not to use just an AC Voltage source of 1V and make the output voltage of the bead divided by the current out of this AC Voltage source? \$\endgroup\$ – mFeinstein Sep 1 '13 at 21:39
  • \$\begingroup\$ That requires a division operation which is not needed with the circuit in the application note. When possible, let the computer do the work. \$\endgroup\$ – Barry Sep 2 '13 at 14:22

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