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Operational amplifier in a TO-5 package, viewed from above.
Gear-shaped heat sinks for TO-5 packages.

In electronics, TO-5 is a designation for a standardized metal semiconductor package used for transistors and some integrated circuits. The TO element stands for "transistor outline" and refers to a series of technical drawings produced by JEDEC.[1]

The typical TO-5 package has a base diameter of 8.9 mm (0.35 in), a cap diameter of 8.1 mm (0.32 in), a cap height of 6.3 mm (0.25 in)[2]. There exist variants with from 2 up to 10 pins. The pins are isolated from the package by individual glass-metal seals, or by a single resin potting. Sometimes one pin is connected directly to the metal case.

There are multiple variants that differ from the regular 3-pin configuration. The H06C variant with 6 pins has its marker between pin 1 and 6, and H08A has 8 pins with the marker on the last one. The counting order is clockwise from the bottom perspective.[3]


  1. ^ "JEDEC TO-5 package specification" (PDF). JEDEC. Archived from the original (PDF) on June 18, 2017. 
  2. ^ TO-5 package at siliconfareast, retrieved 14 December 2013
  3. ^ Metal Can Packages at, retrieved 30 December 2013

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