In electronics, TO-8 is a designation for a standardized metal semiconductor package. TO in TO-8 stands for "transistor outline" and refers to a series of technical drawings produced by JEDEC. The TO-8 package is noticeably larger than the more common TO-5 package. While originally designed for medium power transistors (that is, higher power than TO-5 but lower than TO-3) such as the 2N1483 series or the AD136, it is more commonly used for integrated circuits and sensors (see Variants below).
Construction
The typical TO-8 metal can package has a base diameter of , a cap diameter of , and a cap height of . The lead diameter is nominally . The leads are arranged on a circle with a diameter of . The minimum length of the leads is .
Variants
Several variants of the original TO-8 package have the same cap dimensions but differ in the number and length of the leads (wires). Somewhat incorrectly, TO-8 is often used in manufacturer's literature as a synonym for any package with the cap dimensions of TO-8, regardless of the number of leads, or even for any package with the diameter of TO-8, regardless of the cap height and the number of leads. Light-sensitive or light-emitting devices have a transparent window, lens, or parabolic reflectors in the top of the case rather than a sealed, flat top. There are variants with between 2 and 16 leads. For packages with more than 4 leads, the leads are usually arranged along the edges of a square with a side length of (rather than on a circle as in packages with up to 4 leads or for other metal can packages such as TO-101). These variants usually have a tab to identify lead number 1 and an increased cap diameter of .
National standards TO-233 is intended to replace previous definitions of TO-8.
Standards organizationStandardDesignation forTO-8JEDECJEP95TO-233-AAIECIEC 60191C8/B13DINDIN 418788A3EIAJ / JEITAED-7500ATC-6/TB-7British StandardsBS 3934SO-22/SB3-9
References