Transistor Package Style

12-Lead TO-8 Can

Transistor Can Packages TO-8 Case style, Metal Can

12-Lead TO-8 Package Out-line and TO-8 Dimensions
12-Lead TO-8 Metal Can

The TO-8 is a through-hole metal can, with 12 pins or terminals, alternate contacts are possible. In this case the metal can is isolated from the terminals and may be used to attach a heat sink. The TO-8 package style is larger than a number of other similar packages.

Unlike many other metal-can packages, the leads on this package are not in a circle. Most packages of this type have the leads arrange in a circle. The leads are than spaced some distance apart based on the diameter of the circle. The TO-8 package has its leads in two vertical and two horizontal rows as shown in the diagram.

This package style is used for more than just holding a single transistor, to include transistor arrays and operational amplifiers.
This package may be more common in the high-rel or military area and not so often used in the commercial area, where a surface mount device would be much smaller and operate far better than a through-hole component. Note that each terminal has a bump just off the surface of the metal can which will not allow the flat surface of the can to make contact with the mounting surface. This is most often used to allow air flow under the metal case, or to prevent the hot metal case from making content with the printed wiring board, preventing board damage.

Round metal press-on heat sink
Press-on Heatsink

Editor Note;
Different case dimensions are possible
and still be a TO-8 package.

The heatsink is one possible example.

Related Transistor topics:
Types of Transistor cases
Transistor Derating Guidelines
Manufacturers of FETs and BJTs
Manufacturers of BJT Heatsinks

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Modified 1/21/12
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