Doherty amplifier

A Doherty amplifier comprising:

• a distributor that distributes an input signal inputted to an input terminal into two signals;
• a first amplifier that amplifies one of the two signals and outputs a first amplified signal to a first node;
• a second amplifier that amplifies the other of the two signals and outputs a second amplified signal to a second node;
• a third node that combines the first amplified signal output from the first amplifier and the second amplified signal output from the second amplifier and outputs a combined signal to an output terminal;
• an impedance conversion circuit that has a first end connected to the first node and a second end connected to the third node, and rotates an impedance viewed from the first amplifier to the third node with respect to an impedance viewed from the first amplifier to the first node within a range of 360°±45° on a Smith chart in a second harmonic wave, the second harmonic wave having a twice as high as a frequency of a fundamental wave that is a signal having a center frequency of an operation band;
• and
• a harmonic tuning circuit that has a third end connected to a fourth node positioned on any one of the third node, a first line connecting the first amplifier and the third node, a second line connecting the second amplifier and the third node, and a third line connecting the third node and the output terminal, and makes an absolute value of an impedance with respect to a reference potential at the third end in the second harmonic wave smaller than an absolute value of an impedance with respect to the reference potential at the third end in the fundamental wave;
• wherein an electrical length between the third node and the fourth node is 1/16 or less of the wavelength of the fundamental wave.