COMPOSITE FILTER DEVICE

WIPO Patent Application WO/2022/138140

A1

Provided is a composite filter device which can suppress the occurrence of ripples in a pass band of another band pass filter connected in common.　This composite filter device comprises: a ladder-type filter 10 having at least one series arm resonator including a first series arm resonator S1, and at least one parallel arm resonator including a first parallel arm resonator P1; and at least one band pass filter 11, 12 having one end connected in common with the ladder-type filter 10, wherein the first series arm resonator S1 is closest to a common terminal 13 among series arm resonators S1-S5, the first parallel arm resonator P1 is disposed closest to the common terminal 13 among parallel arm resonators P1-P4, and when the duty of an IDT of the first series arm resonator S1 is defined as Sa, the duty of an IDT of the first parallel arm resonator P1 is defined as Pa, and the duty of an IDT of the remaining series arm resonators S2-S5 and parallel arm resonators P2-P4 is defined as Ta, any one of expressions (1) to (3) below is satisfied.　Expression (1): Sa