An structure used to dissipate heat in devices that are prone to produce heat faster than they can dissipate it themselves. For example: The transistors in a power amplifier have very large amounts of current running through them and can get quite hot. Because they are relatively small the heat cannot dissipate very quickly and can cause failures. As a remedy they are mounted to a heat sink (usually aluminum) that is designed to have much more surface area in contact with the air. Often these heat sinks can be seen on the back of amplifiers and big power supplies as an array of metal “fins.” Some designs employ fans that circulate cooler air over the hot heat sink to further enhance its ability to pull heat away from the components.