LEDs run on direct current (DC), whereas the mains current is alternating current (AC) and usually at a much higher voltage than the LED can accept. LED lamps can contain a circuit for converting the mains AC into DC at the correct voltage. These circuits contain rectifiers, capacitors, and may have other active electronic components, which may also permit the lamp to be dimmed. In an LED filament lamp, the driving circuit is simplified because many LED junctions in series have approximately the same operating voltage as the AC supply. LEDs require a power supply system (driver) to interface them with the electric network. Generally, the current waveform contains some amount of distortion, depending on the luminaries’ technology.