the present invention relates to a driver for driving a gas discharge lamp . in use , the tips of a conventional lamp &# 39 ; s electrodes are subject to tip growth and tip destruction , resulting in decreased or increased arc length , respectively . this has an undesirable effect on the light output of the lamp . the driver of the present invention includes a controller for controlling a current source to the electrodes of the lamp whereby parameters of the current are varied in such a way that tip growth and tip destruction are alternated . as a result , arc length variations stay within certain limits over the lifetime of the lamp .