US Patent 7948331 Thin film balun

There is provided a thin film balun which, while incorporating a capacitor used to supply a DC bias, allows improvement of various required characteristics. A thin film balun according to the present embodiment includes: an unbalanced transmission line which includes two first coils; a balanced transmission line which includes two second coils and which magnetically couples with the unbalanced transmission line; a capacitor having one end connected to the balanced transmission line; and a ground terminal connected to the other end of the capacitor. The capacitor is disposed to have a region which does not overlap a part of coil openings defined by the first coils and the second coils.