Patent ID: 7116203

Claim:
A circuit including a choke coil, comprising: first and second signal lines via which differential transmission communication is performed and on which a power supply current is sent out; third and fourth signal lines via which differential transmission communication is performed and on which the power supply current returns; and a choke coil having first, second, third, and fourth windings, and a magnetic core constituting a closed magnetic path in which the first, second, third, and fourth windings are wound; wherein the first, second, third, and fourth windings are electrically connected to the first, second, third, and fourth signal lines, respectively; the first winding and the second winding are wound in the same direction so that magnetic fluxes generated in the magnetic core are mutually strengthened when an in-phase noise current flows, and the third winding and the fourth winding are wound in the same direction so that magnetic fluxes generated in the magnetic core are mutually strengthened when an in-phase noise current flows; and the first and second windings and the third and fourth windings are wound so that magnetic fluxes generated in the magnetic core are mutually strengthened when an in-phase noise current flows.