Patent ID: 8154348

Claim:
An amplifier circuit operating at a fundamental angular frequency ω 0 , comprising: a transistor which is represented by an equivalent circuit which comprises: an equivalent output current source; a drain-source capacitor as a parallel parasitic capacitor to an output node of said equivalent output current source; and a drain inductor as serial parasitic inductor connected between said equivalent output current source and a drain output node; a harmonic frequency processing circuit which comprises: an input node connected with said drain output node; an output node; a ladder circuit of n (n=1, 2, 3, . . . ) stages provided between said input node and said output node, wherein each of said n stages comprises a parallel capacitor and a serial inductor; a resonant circuit section provided between the output node of said harmonic frequency processing circuit and a ground node and comprising (2n+1) resonators which have resonance frequencies different from each other; and a load resistor provided in a back stage of said harmonic frequency processing circuit, wherein the resonance frequencies of said (2n+1) resonators correspond with frequencies of (n+1) poles and n zeros formed between said drain output node and said ground node in said transistor when said output node of said harmonic frequency processing circuit is short-circuited to said ground node, and wherein the resonant frequencies of 2n resonators of said (2n+1) resonators coincident correspond with a frequency (2ω 0 ) of second harmonic wave to a frequency of (2n+1) th harmonic wave ((2+1)ω 0 ), respectively.