PROBLEM TO BE SOLVED: To provide a load circuit capable of reducing the number of stubs and a highly efficient amplifier circuit using it.
SOLUTION: First stubs respectively have a transmission line length L indicated by L=λ/4m (where m=2, 3, 4,..., n). Of the first stubs T2-Tn, the one having the transmission line length corresponding to m indicated by m=pk (where p is an odd number ≥3 and k is an integer ≥2) is omitted. In the example of n=7, the installation of the first stub T6 is omitted. Even when constituted in such a manner, a characteristic impedance in the load circuit is equivalent to a circuit for which deletion is not performed. Thus, the number of the stubs is reduced. Also, by using a synthetic compensation stub T* instead of a plurality of compensation stubs, the number of the stubs is reduced further. Even when doing so, influence exerted to fundamental waves by residual reactance due to the first stubs can be eliminated.