Impedance circuit, and filter circuit, amplifier circuit, semiconductor integrated circuit, electronic component, and wireless communications device using the same

摘要

The invention seeks to achieve a filter circuit capable of operating in response to more than one frequency band without deteriorating a filter characteristic. One end of an inductor L1 is connected to one end of a capacitor C to form a signal input end. The other end of the inductor L1 is connected to a switch circuit SW1, and the other end of the capacitor C is connected to a switch circuit SW2. When a lower-frequency signal in a 2.4 GHz band is to be inputted, a low-pass filter circuit is formed by connecting the other end of the inductor L1 to a signal output end and the other end of the capacitor C to a ground, and when a higher-frequency signal in a 5 GHz band is to be inputted, a high-pass filter circuit is formed by connecting the other end of the inductor L1 to a ground and the other end of the capacitor C to the signal output end, by manipulating the switch circuits SW1 and SW2.