To provide a variable attenuation circuit that exhibits only small waveform distortions and intermodulation distortion and that is superior in electric power resistance.

The variable attenuation circuit At comprises a distributor for distributing signals to a plurality of paths; a synthesizer for synthesizing the signals passed through the plurality of paths; and a variable-capacitance capacitor Ct, inserted into at least one of the paths, wherein the variable-capacitance capacitor Ct is formed in a manner with a plurality of variable capacitance devices C1 to C5 using thin film dielectric layers whose dielectric constants change depending on applied voltages being connected to each other in parallel, regarding a direct current and connected to each other in series regarding a high frequency, between an input terminal and an output terminal. The variable attenuation circuit At can be realized that can make the maximum use of the rate of a capacitance change in the variable-capacitance capacitor Ct by a bias signal, and exhibits small waveform distortions and intermodulation distortions, and is superior in the electric high power handling capability.

COPYRIGHT: (C)2005,JPO&NCIPI