What is the difference between Ls and Lp? Which one should I choose?

Should you choose Ls or Lp – or Cs or Cp? This is a frequently asked question.

General rule:

Low impedance |Z| of the component (<10Ω) → series equivalent circuit

High impedance |Z| of the component (≥10kΩ) → parallel equivalent circuit

In the range between 10Ω and 10kΩ, follow the component manufacturer’s recommendation if available.

For inductors, impedance increases with frequency:

For capacitors, impedance decreases with frequency:

So: for high inductance and/or frequency, use the parallel equivalent circuit; for low inductance and/or frequency, use the series equivalent. For high capacitance and/or frequency, choose the series equivalent; for low capacitance and/or frequency, choose the parallel equivalent.

Note: At very high frequencies, the winding capacitance of a coil becomes dominant and the impedance decreases significantly. In this range, reliable inductance measurement is no longer possible as the coil behaves like a capacitor.

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