Patent ID: 8649738

Claim:
A high-frequency amplifier comprising: an amplification section having a function to convert an input signal from a voltage signal into a current signal and output said current signal; output terminals; and a load circuit which is connected to the output node of said amplification section and outputs said current signal output by said amplification section to said output terminals as a voltage signal, wherein said load circuit has a first reactance element, a second reactance element and a third reactance element, wherein a specific one of the two end nodes of said first reactance element is connected to a specific one of the two end nodes of said second reactance element at a connection point connected to said output node of said amplification section, wherein the other one of said two end nodes of said second reactance element is connected to a specific one of the two end nodes of said third reactance element at a connection point connected to a specific one of said output terminals, wherein the other one of said two end nodes of said first reactance element and the other one of said two end nodes of said third reactance element are connected to the other one of said output terminals so that said first reactance element and said third reactance element form a parallel circuit connected said other output terminal, wherein each of said first reactance element and said second reactance element is a capacitive reactance element or an inductive reactance element, wherein said third reactance element is an inductive reactance element or a capacitive reactance element, wherein the reactance of each of said first reactance element and said second reactance element is variable, wherein said load circuit includes a tap capacitor resonator including: said first reactance element implemented as a first variable-capacitance capacitor having a variable capacitance, said second reactance element implemented as a second variable-capacitance capacitor having a variable capacitance; and said third reactance element implemented as an inductor, wherein said first variable-capacitance capacitor serving as said first reactance element and a constant-capacitance capacitor having a constant capacitance are connected in parallel to said output node of said amplification section.