Patent ID: 7176757

Claim:
A multistage amplifying device for amplifying a desired signal having a desired frequency band and outputting the amplified desired signal, comprising: first to N-th (N is a natural number of 2 or more) amplifiers connected in cascade, wherein the k-th (k is a natural number of 1 to N) amplifier includes: a k-th amplification section; and a k-th feedback section which has a reactance component, changes a phase of a signal output from the k-th amplification section and negatively feeds the resultant signal back to an input side of the k-th amplification section, wherein, when a difference between a phase of a frequency component of the desired frequency band included in a signal output from the N-th amplifier and a phase of a third-order inter-modulation distortion included in a signal output from the (N−1)-th amplifier is referred to as a first phase, and a difference between the phase of the frequency component of the desired frequency band included in the signal output from the N-th amplifier, and a phase of a combined third-order inter-modulation distortion obtained by combining a third-order inter-modulation distortion occurring in the N-th amplification section and a third-order inter-modulation distortion fed back from the N-th feedback section is referred to as a second phase, a difference between the first phase and the second phase is 120° or more and 180° or less.