A fluorescent lamp ballast for pulsed-mode operation and the use of a self-excited or externally controlled half or full bridge circuit for the same purpose are disclosed. An electronic ballast of that type has a buffered direct voltage supply (Udc, udc) that may be drawn from the effective power for the fluorescent lamp or lamps. The load circuit in which the fluorescent lamps are arranged has a choke (L1) connected in series, or if necessary a capacitor (C1) may be connected in parallel to the fluorescent lamp for starting purposes. Such a circuit should be designed in such a way that it allows the characteristic values of the fluorescent lamp light, i.e. its luminosity factor and colour temperature, to be modified without mechanically switching the choke. For that purpose, at least one electronic switching element (S1) or at least one pair of such switching elements (S1, S2, S3, S4) periodically supply the choke (L1) and the fluorescent lamp with voltage pulses (uac). The pairs of switching elements and the voltage pulses (uac) may be frequency-modulated (f1, f2) by means of a control signal (f). This frequency-modulation may be ensured by gradual or continuously periodical frequency alternation (sinusoidally), so that the frequency is constantly modified and no disturbing or standing waves that could provoke an optical flickering are formed in the fluorescent lamp.