A class-D amplifier, or switching amplifier, is an electronic amplifier where all power devices (usually MOSFETs) are operated as binary switches. They are either fully on or fully off. Ideally, zero time is spent transitioning between those two states. In this way, power loss is significantly reduced, making a D class amplifier anywhere from 75% to 95% efficient. To maintain high efficiency, the filter is made with purely reactive components (inductors and capacitors), which store the excess energy until it is needed instead of converting some of it into heat. Some other advantages include reduction in size and weight, reduced power waste as heat dissipation and hence smaller (or no) heat sinks, and reduction in cost due to smaller heat sink and compact circuitry.