A class-F amplifier circuit by which the transistor load impedance, for even-order higher harmonics, can be kept "zero" and that for odd-order higher harmonics can be kept "open" without affecting the impedance at the fundamental frequency has been developed. This circuit basically consists of transmission lines with lengths equal to a half wavelength and a quarter wavelength at the fundamental frequency where the residual reactance at the fundamental frequency, due to the higher harmonic-frequency circuits, is compensated. Using this circuit, a microwave heterojunction bipolar transistor amplifier was designed using a harmonic-balance simulator. The designed power-added efficiency was more than 90%. The output waveforms, a dynamic load line, and the input/output power response were evaluated.