An inverter stage includes a supply voltage terminal and a reference potential terminal. An npn transistor has a base terminal for receiving an input signal, a collector terminal for supplying an output signal, and an emitter terminal. A controllable current source is connected between the emitter terminal of the transistor and the reference potential terminal. A series circuit of at least two diodes is connected between the supply voltage terminal and the collector terminal of the transistor. A symmetrical inverter stage assembly includes two of the inverter stages being connected in parallel with the emitters of the transistors of each of the inverter stages being connected to one another. A ring oscillator includes n (n.gtoreq.1) of the inverter stages connected in series. The inverter stages include first and last inverter stages, each of the inverter stages has an output and an input, and the output of the last inverter stage is connected to the input of the first inverter stage.