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Four views of the TO-220 package

The TO-220 is a style of electronic component package, commonly used for transistors, silicon-controlled rectifiers, and integrated circuits. TO-220 packages commonly have three leads although units with two, four, or five leads are also manufactured. A notable characteristic is a metal tab with a hole, used in mounting the case to a heatsink. Components made in TO-220 packages can handle more power than those constructed in TO-92 cases.

TO-220 packages are heatsinkable, and thus can be used in projects where a large amount of power is being drawn. The top of the package has a metal tab with a hole used in mounting the component to a heatsink. Thermal compound is also used to provide greater heat transfer.

The metal tab is often connected electrically to the internal circuitry. This does not normally pose a problem when using isolated heatsinks, but a mica insulator may be required to electrically isolate the component from the heatsink if the heatsink is grounded. Mica insulators are favorable because they have excellent thermal conductivity while acting as an electrical insulator.

In applications where vertical clearance is at a premium (such as ISA cards in computers), it is often feasible to bend the leads at a right angle and mount the component flat to the printed wiring board using a screw and nut. This often provides enough surface area to heatsink the component when power dissipation is moderately high.

• Can be used in high-power and high-current applications where equivalent components of other cases may be susceptible to damage.
• Grounding area makes handling easier by reducing the possibility of damage from electrostatic discharge.
• Mounting with the tab ensures the component to be held firmly in place.

• More costly than equivalent components of other cases.
• Footprint requires considerably more surface area on a printed wiring board than other case styles. Heatsinks require even more board area.
• In the case of chassis-mounting, space must be dedicated to the components and/or their heatsinks, thereby increasing production costs.

Common Voltage Regulators:

• 7805, +5-volt regulated output
• 7812, +12-volt regulated output
• LM317, voltage regulator
• LM317T, voltage regulator
• LM340, voltage regulator