A LED retrofit lamp for replacement of fluorescent lamp or tube driven by fluorescent ballast is provided. The retrofit lamp is compatible with the fluorescent ballast that requires the presence of a barrier for striking an arc voltage. The present invention provides a strike barrier—a controllable barrier that does not allow current conduction until a threshold voltage is reached. When a current above the threshold voltage passes through the strike barrier, the circuit latches and allows conduction at normal voltage. The present invention also provides a circuit that replicates the cathode heater resistance of a fluorescent lamp to rapid start and programmed start ballast.