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An electronic component that stores an electric charge and releases it when required. It comes in a huge variety of sizes and types for use in regulating power as well as for conditioning, smoothing and isolating signals. Capacitors are made from many different materials, and virtually every electrical and electronic system uses them.

Somewhat Like a Battery
Capacitors act like tiny storage batteries that charge and discharge rapidly. Made of two plates separated by a thin insulator or sometimes air, when one plate is charged negative and the other positive, a charge builds up and remains after the current is removed. When power is required, the circuit is switched to conduct current between the plates, and the charge is released. See ultracapacitor.

Many Applications
Big capacitors are used in computer power supplies. Tiny discrete ceramic and tantalum capacitors are built on the outside of the chip package or surround the chip on the motherboard. In signal processing, a capacitor and resistor smooth the spikes and sharp edges from a signal. In DRAM chips, capacitors are microscopic cells that hold the 0s and 1s (bits). Logic circuits, which are mostly transistors and resistors, may also contain capacitors. See tantalum capacitor and ferroelectric capacitor.


Silver Batteries
Looking like "silver cans," and acting like miniature storage batteries, capacitors are found on countless circuit boards such as this high-end display adapter. Wired between the power and ground planes, they quickly charge up when the computer is turned on. When more transistors switch simultaneously because the application demands extra processing, they are made to release their charge. (Image courtesy of NVIDIA Corporation.)

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