An irreversible circuit element includes first and second high pass isolators each including first and second center electrodes intersecting with and being insulated from each other on a ferrite to which a direct-current magnetic field is applied with a permanent magnet. One end of the first center electrode is an output port and the other end thereof is an input port, and one end of the second center electrode is another output port and the other end thereof is a ground port. A pass frequency band of the first isolator is higher than a pass frequency band of the second isolator. Respective output portions of the first and second isolators are electrically connected and defined as one output terminal, and a low pass filter LPF is inserted between the output terminal and the output port of the second isolator.

A non-reciprocal circuit element includes a ferrite, a first central electrode and a second central electrode arranged on the ferrite so as to cross each other in an insulated state, and a permanent magnet that applies a DC magnetic field to a portion where the first and second central electrodes cross each other. One end of the first central electrode defines an input port, and the other end thereof defines an output port. One end of the second central electrode defines the input port, and the other end thereof defines a ground port. A resistance element and a capacitance element, which are connected in parallel with each other, are connected in series with and between the input port and the output port. Input impedance is lowered by making inductance of the second central electrode relatively large.

A non-reciprocal circuit element includes a ferrite, a first central electrode and a second central electrode arranged on the ferrite so as to cross each other in an insulated state, and a permanent magnet that applies a DC magnetic field to a portion where the first and second central electrodes cross each other. One end of the first central electrode defines an input port, and the other end thereof defines an output port. One end of the second central electrode defines the input port, and the other end thereof defines a ground port. A resistance element and a capacitance element, which are connected in parallel with each other, are connected in series with and between the input port and the output port. Input impedance is lowered by making inductance of the second central electrode relatively large.