a circuit for generating a triangular voltage across a capacitor having a charging current source and a discharging current source for the capacitor . a comparison stage compares the generated voltage with a first and a second reference voltage , respectively , from a voltage divider and controls the generation of a setting and a resetting signal , respectively , at a bistable switching element when the value of the first and the second reference voltage , respectively , is reached . the bistable element controls a switch which determines charging or discharging , respectively , of the capacitor . the circuit is suitable for high repetition rates because of the fact that a buffer stage is connected to the capacitor for deriving , under the control of the capacitor voltage , a supply voltage for the bistable switching element which is of the same order of magnitude and varies in the same direction as the generated triangular voltage . preferably , the switch and the bistable switching element do not employ pnp - transistors .