TO-5

The TO element stands for "transistor outline" and refers to a series of technical drawings produced by JEDEC.

[1] The pins are isolated from the package by individual glass-metal seals, or by a single resin potting.

Several variants of the original TO-5 package have the same cap dimensions but differ in the number and length of the leads (wires).

Somewhat incorrectly, TO-5 and TO-39 are often used in manufacturer's literature as synonyms for any package with the cap dimensions of TO-5, regardless of the number of leads, or even for any package with the diameter of TO-5, regardless of the cap height and the number of leads.

For transistors, the fourth wire is typically connected to the metal case as a means of electromagnetic shielding for radio frequency applications.

This allows a slightly increased chip area in a cap of unchanged diameter.

This allows a slightly increased chip area in a cap of unchanged diameter.

TO-205 is intended to replace previous definitions of packages with leads arranged in a circle with a diameter of 5.08 mm (0.200 in).

A new package with 3 leads and a cap height of 4.32 mm (0.170 in) (similar to TO-78 / TO-99) is added as TO-205-AF.

Transistor in a TO-5 package with 25 mm leads.
Gear-shaped heat sinks for TO-5 packages.
Resistive opto-isolator VTL2C1 in a TO-33 package
Voltage regulator integrated circuit ( Tesla MAA723) in a TO-76 package.
Sample-and-hold integrated circuit ( Tesla MAC198) in a reduced-height TO-99 package.
Voltage reference integrated circuit ( National Semiconductor LH0070) in a TO-205-AF package