In electronics, TO-18 is a designation for a style of transistor metal case. The case is more expensive than the similarly sized plastic TO-92 package. The name is from JEDEC, signifying Transistor Outline Package, Case Style 18. [1]
The typical TO-18 metal can package has a base diameter of 5.6 mm (0.22 in), a cap diameter of 4.70 mm (0.185 in), a cap height of 4.83 mm (0.190 in). [1] The tab is located 45° from pin 1, which is typically the emitter. The lead diameter is nominally 0.45 mm (0.018 in). The leads are arranged in a circle with a diameter of 2.54 mm (0.100 in). The minimum length of the leads is 12.7 mm (0.50 in).
Different manufacturers have different tolerances, and the actual form factor may vary slightly, depending on function.
The 3-lead TO-18 is used for transistors and other devices using no more than three leads. Variants for diodes, photodiodes and LEDs may have only two 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. For example, diode lasers such as those found in CD players may be packaged in TO-18 cases with a lens.
There are variants with between 2 and 8 leads.
The TO-46 [2] and TO-52 [3] packages have 3 leads. These packages differ from all other variants in the height of the cap. Instead of 4.83 mm (0.190 in) the cap height is only 3.30 mm (0.130 in) for TO-52 and 1.90 mm (0.075 in) for TO-46.
The package with 4 leads but otherwise with dimensions identical to TO-18, is standardized as TO-72. [4] The fourth wire is typically connected to the metal case as a means of electromagnetic shielding for radio frequency applications.
The TO-71 package has 8 leads (up to three of those may be omitted). [5] The minimum angle between two adjacent leads is 45°.
TO-206 is intended to replace previous definitions of packages with leads arranged in a circle with a diameter of 2.54 mm (0.100 in). [6] [7] The different outlines are now defined as variants of TO-206: TO-18 is renamed to TO-206-AA, TO-46 to TO-206-AB, TO-52 to TO-206-AC, TO-72 to TO-206-AF. A new package with 3 leads and a cap height of 1.40 mm (0.055 in) (i.e. smaller than TO-46) is added as TO-206-AD. TO-206-AE does not require a minimum diameter of the leads but is otherwise identical to TO-18. The somewhat unrelated TO-58 package is included as TO-206-AG.
Standards organization | Standard | Designation for | |||
---|---|---|---|---|---|
TO-18 | TO-46 | TO-71 | TO-72 | ||
JEDEC | JEP95 [7] | TO-206-AA | TO-206-AB | — | TO-206-AF |
IEC | IEC 60191 [lower-alpha 1] [8] | C7/B11 | C10/B11 | C7/B12 | |
DIN | DIN 41876 [9] [8] | 18A3 | 18A4 | ||
EIAJ / JEITA | ED-7500A [lower-alpha 1] [10] | TC-7/TB-8C, TC-7/TB-16C | — | — | TC-7/TB-9C |
British Standards | BS 3934 [lower-alpha 1] [11] [12] | SO-12A/SB3-6A | SO-12C/SB3-6A | SO-12A/SB8-1B | SO-12A/SB4-3 |
Gosstandart | GOST 18472—88 [13] | KT-1-7 [lower-alpha 2] | KT-35-7 [lower-alpha 3] | — | KT-1-12 [lower-alpha 4] |
Rosstandart | GOST R 57439 [14] | ||||
Kombinat Mikroelektronik Erfurt | TGL 11811 [15] | A3/15-3a | — | — | A4/15-4a |
TGL 26713/07 [15] | F1BA3 | — | — | F1CA3 |
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The JEDEC Solid State Technology Association is an independent semiconductor engineering trade organization and standardization body headquartered in Arlington County, Virginia, United States.
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Mullard Limited was a British manufacturer of electronic components. The Mullard Radio Valve Co. Ltd. of Southfields, London, was founded in 1920 by Captain Stanley R. Mullard, who had previously designed thermionic valves for the Admiralty before becoming managing director of the Z Electric Lamp Co. The company soon moved to Hammersmith, London and then in 1923 to Balham, London. The head office in later years was Mullard House at 1–19 Torrington Place, Bloomsbury, now part of University College London.
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TO-66 is a type of semiconductor package for devices with three connections, such as transistors. The shape is similar to the TO-3 package, but the size is smaller. The TO-66 package is made entirely of metal and is commonly used by silicon controlled rectifiers and power transistors. In Europe, it was popularly used by the complementary germanium power transistors AD161/AD162.
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