An object of the present invention is to provide a radio frequency power amplifier of multi stage amplifying method that is designed to reduce instability of output power caused by electromagnetic coupling of bias supply terminals and interconnections of each stage to thereby operate stably. An anode is disclosed having a metal source as well as a current collector that together function as an active, reversible, working anode. An extension arm is pivotally attached to the upper portion of the tree-interface bar.