Abstract: To achieve a filter circuit that is configured to have a good frequency rejection characteristic and suppress an increase in size due to mounting, in a more preferred aspect. A filter circuit includes a first signal line that is arranged to extend longitudinally, and a second signal line that is arranged to extend in parallel with the first signal line, in which the second signal line has one end that is electrically connected to the first signal line, and the other end that is open, in a longitudinal direction, and a length in the longitudinal direction that is determined according to a frequency of a signal to be blocked of signals transmitted through the first signal line.

Abstract: To achieve a filter circuit that is configured to have a good frequency rejection characteristic and suppress an increase in size due to mounting, in a more preferred aspect. A filter circuit includes a first signal line that is arranged to extend longitudinally, and a second signal line that is arranged to extend in parallel with the first signal line, in which the second signal line has one end that is electrically connected to the first signal line, and the other end that is open, in a longitudinal direction, and a length in the longitudinal direction that is determined according to a frequency of a signal to be blocked of signals transmitted through the first signal line.

Abstract: An electrostatic discharge (ESD) protection device that protects a power amplifier from ESD. The ESD protection device includes a filter circuit connected to an antenna line of a wireless communication apparatus and that passes an ESD component having a predetermined frequency or less, a detection circuit that converts an output of the filter circuit into an analog DC output, a level determination circuit that detects that the analog DC output of the detection circuit is a predetermined threshold value or more, and a control interrupt circuit that controls a state of the power amplifier in accordance with an output of the level determination circuit.

Abstract: An electrostatic discharge (ESD) protection device that protects a power amplifier from ESD. The ESD protection device includes a filter circuit connected to an antenna line of a wireless communication apparatus and that passes an ESD component having a predetermined frequency or less, a detection circuit that converts an output of the filter circuit into an analog DC output, a level determination circuit that detects that the analog DC output of the detection circuit is a predetermined threshold value or more, and a control interrupt circuit that controls a state of the power amplifier in accordance with an output of the level determination circuit.