| 摘要 |
PROBLEM TO BE SOLVED: To solve the following problems: although the cut off frequency of an LPF is decided by a capacitance value and a resistance value of the junction capacitance in a noise filter (LPF) which uses the junction capacitance of a diode, a cut off frequency not larger than 5 MHz is required for obtaining sufficient RFI removal characteristics; and then a chip size is enlarged when the capacitance value is made to be increased, while input loss is increased when the resistance value is made to be increased since any one of the capacitance value and the resistance value is required to be increased. SOLUTION: The noise filter configures a ladder-type LPF by: a first capacitive element 10 composed of a transistor where diode connection of two terminals among three terminals are performed; and a second capacitive element 20 which connects a pn-junction capacitive element in parallel with an insulating capacitive element. Increase in an occupied area can be prevented even though the capacitance value is made to be increased in order to connect the pn junction capacitive element to be provided in a semiconductor layer in parallel with the insulated capacitive element 20b to be provided on its surface by making approximately overlapped with each other. The second capacitive element having the insulated capacitive element can be protected from ESD since the first capacitive element has snap back characteristics, while high enhancement of EDS can be achieved by having small and high performance RFI removal characteristics. COPYRIGHT: (C)2010,JPO&INPIT |
