Patent ID: 8143968

Claim:
A thin film balun comprising: an unbalanced transmission line which includes a pair of first coils disposed side by side on a same surface; a balanced transmission line which includes a pair of second coils and is electromagnetically coupled to the unbalanced transmission line, the pair of second coils being disposed on a different surface from that of the pair of first coils and being opposed to the pair of first coils; a first electrode which is connected to both of the second coils constituting the balanced transmission line and constitutes a capacitor; a second electrode which is connected to a ground terminal and disposed to be opposed to the first electrode and constitutes the capacitor; and a DC supply terminal which is connected to the pair of second coils constituting the balanced transmission line and the first electrode constituting the capacitor, wherein the second electrode has a section opposed to at least one of the first coils and the second coils, the section being formed with a section opposed to the first electrode.