A retrofit lamp is for use with a fluorescence lighting ballast. The retrofit lamp comprises a filament emulation circuit. A detection circuit detects (at least) if a connected ballast is an instant start electronic ballast or an electromagnetic ballast by detecting a potentially existing heating voltage across the filament emulation circuit. In response, an LED arrangement may be connected in a series configuration (for an instant start electronic ballast) or in a parallel configuration (for an electromagnetic ballast). In this way, the output power is managed to ensure efficient operation. A different pin safety function may also be provided in the different configurations.