Abstract: In a feed forward amplifier, an RF amplifier is supplied with an input RF signal at an input terminal for amplifying the same; a distortion extraction loop supplied with the input RF signal and further with the output RF signal from the RF amplifier is for extracting non-linear distortion components formed in the output RF signal as a result of amplification in the RF amplifier; a variable phase shifter is provided in the distortion extraction loop for varying a phase of the input RF signal; a variable attenuator is provided in the distortion extraction loop for attenuating an amplitude of the input RF signal that has been supplied to the distortion extraction loop; and a distortion extraction circuit is provided in the distortion extraction loop for producing a distortion output signal that includes non-linear components; further, a control circuit is supplied with the input signal and with the distortion output signal for extracting a main signal component contained in the distortion output signal.