MATCHING CIRCUIT FOR VACUUM TUBE

PROBLEM TO BE SOLVED: To provide a matching circuit for a vacuum tube capable of suppressing an amount of a high-frequency power required for obtaining a predetermined vacuum tube output.SOLUTION: A matching circuit 10A for a vacuum tube is an impedance matching circuit provided between a high-frequency power source 5 and a control grid 7c of a vacuum tube 7. The matching circuit 10A comprises: a conductive member 12 including an inductance component at a frequency band of a high-frequency power, and having a connection point B1 connected with the control grid 7c and a connection point B2 connected with the power source 5; a resistance element 14 connected between a connection point B3 of the conductive member 12 and a reference potential line 20; a capacitive element 16 connected between a connection point B4 of the conductive member 12 and the reference potential line 20; and a capacitance 22 generated between the control grid 7c and the reference potential line 20. In a predetermined direction A in the conductive member 12, the connection points B2 and B3 are located between the connection point B1 and the connection point B4.