Abstract: A filter circuit includes: a wiring pattern provided in an upper wiring layer of a printed circuit board, a wiring pattern provided in a lower wiring layer of the printed circuit board, a wiring pattern extending from one end of the wiring pattern, a wiring pattern provided so as to partially face the wiring pattern in the upper wiring layer, a bypass capacitor provided in the upper wiring layer and connected to the wiring pattern and a ground conductor surface, a via connecting one end of the wiring pattern and the wiring pattern, and a via connecting the wiring pattern and the wiring pattern. A structure including the wiring pattern, the via, and the wiring pattern faces a structure including the via and the wiring pattern.

Abstract: A printed circuit board includes a line formation layer including a differential line having a first conductor and a second conductor, a first component for a countermeasure against a surge, a first connection conductor having one end connected to the first conductor and another end connected to the first component, a second component for a countermeasure against a surge, a second connection conductor having one end connected to the second conductor and another end connected to the second component, a ground layer, and a dielectric mounted between the line formation layer and the ground layer. Lengths of the first conductor and second conductor are adjusted based on a difference of capacitance values in the circuit board.

Abstract: A first capacitance C1 exists between a first connection conductor (21) as well as a first component (31) and a ground layer (3), and a second capacitance C2 exists between a second connection conductor (22) as well as a second component (32) and the ground layer (3). The length of the first conductor (11) and the length of the second conductor (12) are each adjusted depending on a difference ?C between the first capacitance C1 and the second capacitance C2.