EMC Question of the Week: April 19, 2021

Components on a circuit board

The two identical components in the center of the figure are   

  1. 0-Ω resistors
  2. inductors
  3. ferrite beads
  4. tantalum capacitors


The correct answer is “c.” The components labeled L26 and L27 are ferrite beads. It's not uncommon for ferrite beads to be labeled with an "L" even though they have more resistance than inductance over their useful frequency range. Many circuit boards label ferrite beads using an "F" or "FB," which helps to make it clear that they are not inductors.  

Of course, with no other information, it would be impossible to say with absolute certainty that these components were not inductors. Nevertheless, SMT inductors usually have a distinctive geometry or coloring that distinguishes them from other SMT components.  

Note that his board uses via-in-pad technology. Placing vias in the solder pads helps to minimize connection inductance and conserve board area.

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