The transistor circuit 1 includes a plurality of transistor cells 10 each having a transistor 11, a base ballast resistor 12, a capacitor 13, and an inductor 14. The transistors 11 have the respective collectors commonly connected to a collector terminal 1c of the transistor circuit 1 and the respective emitters commonly connected to an emitter terminal 1e thereof. Each base ballast resistor 12 is connected to bases of the transistor 11 at one end and to a base terminal 1b of the transistor circuit 1 at the other end. The capacitor 13 is serially connected to the inductor 14, thus to form a serial resonant circuit 15, which is connected in parallel with the base ballast resistor 12 and provided between the bases of the transistor 11 and the base terminal 1b of the transistor circuit 1 and connected thereto.
