The basics of the common mode choke

2014-1-21

The impedance of an inductor is proportional to its inductance and the frequency of the signal passing through it.  Inductors, therefore, can act like low-pass filters, that is they allow low frequency signals to pass through them, while they block higher frequency signals.  A common mode choke is a special type of filter with two inductor windings on the same core.  In order to understand common mode chokes, it is important to first understand what common mode means.