Patent ID: 8044720

Claim:
An amplification circuit comprising: a semiconductor amplification element; a current feedback circuit connected to a terminal close to a ground side of the semiconductor amplification element and can control gain reduction; and a voltage feedback circuit connected between an input terminal and an output terminal of the semiconductor amplification element and can control feedback voltage, wherein the feedback voltage of the voltage feedback circuit varies according to the gain reduction controlled by the current feedback circuit, wherein the feedback voltage of the voltage feedback circuit is increased as the gain reduction controlled by the current feedback circuit is increased, wherein the feedback voltage of the voltage feedback circuit is decreased as the gain reduction controlled by the current feedback circuit is decreased, wherein the current feedback circuit has a first resistance portion with a variable resistance value, and controls the gain reduction according to the resistance value of the first resistance portion, wherein the voltage feedback circuit has a second resistance portion with a variable resistance value and controls the feedback voltage according to the resistance value of the second resistance portion, wherein the resistance value of the second resistance portion is decreased when the resistance value of the first resistance portion is increased, and wherein the resistance value of the second resistance portion is increased when the resistance value of the first resistance portion is decreased.