Cross section of a 2N2222 in the TO-18 package

electronics The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons using electronic devices. Electronics uses active devices to control electron flow by amplification ...

, TO-18 is a designation for a style of

transistor upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink). A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch e ...

metal case. The case is more expensive than the similarly sized plastic

TO-92 The TO-92 is a widely used style of semiconductor package mainly used for transistors. The case is often made of epoxy or plastic, and offers compact size at a very low cost. History and origin The JEDEC TO-92 descriptor is derived from the or ...

package. The name is from

JEDEC The JEDEC Solid State Technology Association is an independent semiconductor engineering trade organization and standardization body headquartered in Arlington County, Virginia, United States. JEDEC has over 300 members, including some of the w ...

, signifying ''Transistor Outline Package, Case Style 18''.

Construction and orientation

The typical TO-18 metal can package has a base diameter of , a cap diameter of , a cap height of . The tab is located 45° from pin 1, which is typically the emitter. The lead diameter is nominally . The leads are arranged in a circle with a diameter of . The minimum length of the leads is . Different manufacturers have different tolerances, and the actual form factor may vary slightly, depending on function.

Uses and variants

The 3-lead TO-18 is used for transistors and other devices using no more than three leads. Variants for

diode A diode is a two-terminal electronic component that conducts current primarily in one direction (asymmetric conductance); it has low (ideally zero) resistance in one direction, and high (ideally infinite) resistance in the other. A diode ...

photodiode A photodiode is a light-sensitive semiconductor diode. It produces current when it absorbs photons. The package of a photodiode allows light (or infrared or ultraviolet radiation, or X-rays) to reach the sensitive part of the device. The packag ...

s and

LED A light-emitting diode (LED) is a semiconductor Electronics, device that Light#Light sources, emits light when Electric current, current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy i ...

s 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 laser The laser diode chip removed and placed on the eye of a needle for scale A laser diode (LD, also injection laser diode or ILD, or diode laser) is a semiconductor device similar to a light-emitting diode in which a diode pumped directly with e ...

s such as those found in

CD players A CD player is an electronic device that plays audio compact discs, which are a digital optical disc data storage format. CD players were first sold to consumers in 1982. CDs typically contain recordings of audio material such as music or aud ...

may be packaged in TO-18 cases with a lens. There are variants with between 2 and 8 leads.

TO-46 / TO-52

The TO-46 and TO-52 packages have 3 leads. These packages differ from all other variants in the height of the cap. Instead of the cap height is only for TO-52 and for TO-46.

TO-72

The package with 4 leads but otherwise with dimensions identical to TO-18, is standardized as TO-72. The fourth wire is typically connected to the metal case as a means of

electromagnetic shielding In electrical engineering, electromagnetic shielding is the practice of reducing or blocking the electromagnetic field (EMF) in a space with barriers made of conductive or magnetic materials. It is typically applied to enclosures, for isolating ...

for

radio frequency Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around to around . This is roughly between the upp ...

applications.

TO-71

The TO-71 package has 8 leads (up to three of those may be omitted). The minimum angle between two adjacent leads is 45°.

TO-206

TO-206 is intended to replace previous definitions of packages with leads arranged in a circle with a diameter of . 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 (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.

National standards

} , rowspan=2, KT-35-7 , rowspan=2, — , rowspan=2, KT-1-12 , - ,

Rosstandart Federal Technical Regulation and Metrology Agency (Rosstandart) (russian: Федеральное агентство по техническому регулированию и метрологии (Росстандарт)) is the Russian federal ...

GOST GOST (russian: ГОСТ) refers to a set of International standard, international Technical standard, technical Standardization, standards maintained by the ''Euro-Asian Council for Standardization, Metrology and Certification (EASC)'', a region ...

R 57439 , - , rowspan=2,

Kombinat Mikroelektronik Erfurt VEB Kombinat Mikroelektronik Erfurt was an important manufacturer of active electronic components in East Germany. It should not be confused with the more well-known VEB Kombinat Robotron Dresden which used integrated circuits from Kombinat M ...

, TGL 11811 , A3/15-3a , — , — , A4/15-4a , - , TGL 26713/07 , F1BA3 , — , — , F1CA3

References

External links

TO-18 Package
EESemi.com {{DEFAULTSORT:TO-018 Semiconductor packages