FEEDFORWARD AMPLIFIER

PROBLEM TO BE SOLVED: To provide distortion suppression quantity more than a specified value while attaining miniaturization by providing a filter inside a distortion detection loop or a distortion removal loop and parallelly setting plural filters to a signal line. SOLUTION: An output from a signal synthesizing part 7 is amplified through a vector adjuster 8 of a distortion detection loop through an auxiliary amplifier 9 while being mainly occupied with distortion quantity at a main amplifier 4. When the main amplifier 4 applies a high output such as 43dBm, plural filters 6 are parallelly inserted so that the characteristics of its frequency, phase and amplitude can become inverted in phase, and flattening in the phase and amplitude characteristics is attained to the frequency. On the other hand, the signal from the main amplifier 4 is transmitted through a directional coupler 5 and a filter 11 of a distortion removal loop to the signal synthesizing part of the directional coupler 12. At such a time, the plural filters 11 inverted in phase and amplitude characteristics are parallelly inserted so as to cancel the frequency characteristics of the auxiliary amplifier 9, the phase and amplitude characteristics are flattened and the distortion suppressing quantity more than 40dB can be secured.