The TO-92 is a widely used style of
semiconductor package
A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way. ...
mainly used for
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 ...
s. The case is often made of
epoxy
Epoxy is the family of basic components or cured end products of epoxy resins. Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers which contain epoxide groups. The epoxide functional group is also coll ...
or
plastic
Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adaptab ...
, and offers compact size at a very low cost.
History and origin
The
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 ...
TO-92 descriptor is derived from the original full name for the package: Transistor Outline Package, Case Style 92.
The package is also known by the designation
SOT54.
By 1966 the package was being used by Motorola for their
2N3904 devices among others.
Construction and orientation
![Transistorer (cropped)](https://upload.wikimedia.org/wikipedia/commons/2/21/Transistorer_%28cropped%29.jpg)
The case is molded around the transistor elements in two parts; the face is flat, usually bearing a machine-printed part number (some early examples had the part number printed on the top surface instead). The back is semi-circularly-shaped. A line of moulding flash from the injection-moulding process can be seen around the case.
The leads protrude from the bottom of the case. When looking at the face of the transistor, the leads are commonly configured from left-to-right as the ''emitter'', ''base'', and ''collector'' for 2N series (JEDEC) transistors, however, other configurations are possible, such as ''emitter'', ''collector'', and ''base'' commonly used for 2S series (Japanese) transistors or ''collector'', ''base'', and ''emitter'' for many of the BC series (
Pro Electron Pro Electron or EECA is the European type designation and registration system for active components (such as semiconductors, liquid crystal displays, sensor devices, electronic tubes and cathode ray tubes).
Pro Electron was set up in 1966 in Bru ...
) types.
If the face has a part name made up of only one letter and a few numbers, it can be either a Japanese or a Pro Electron part number. Thus, "C1234" would likely be a 2SC1234 device, but "C547" is usually short for "BC547".
![To-92 footprint](https://upload.wikimedia.org/wikipedia/commons/c/c8/To-92_footprint.jpg)
The leads coming out of the case are spaced 0.05" (1.27 mm) apart. It is often convenient to bend them outward to a 0.10" (2.54 mm) spacing to make more room for wiring. Units with their leads pre-bent may be ordered to fit specific board layouts, depending on the application. Otherwise, the leads may be bent manually; however, care must be taken as they can break easily, as with any other device that is manually configured.
The physical dimensions of the TO-92 housing may vary slightly depending on the manufacturer, however, the 1.27mm lead spacing must be respected.
Advantages
* Transistors of this type can be made very inexpensively and take up very little board space. Most models are readily available in large quantities from wholesale distributors.
* They are easy to find in small electronics stores because of their wide usefulness, making them a popular choice for hobby work and
prototyping
A prototype is an early sample, model, or release of a product built to test a concept or process. It is a term used in a variety of contexts, including semantics, design, electronics, and software programming. A prototype is generally used to ...
.
Disadvantages
The main disadvantage of this style of case is the lack of
heat sink
A heat sink (also commonly spelled heatsink) is a passive heat exchanger that transfers the heat generated by an electronic or a mechanical device to a fluid medium, often air or a liquid coolant, where it is dissipated away from the device, th ...
ing.
* Transistors and ICs of these types cannot handle as much power as higher-power equivalents, such as the
TO-220
The TO-220 is a style of electronic package used for high-powered, through-hole components with pin spacing. The "TO" designation stands for "transistor outline". TO-220 packages have three leads. Similar packages with two, four, five or seven ...
, and can burn out quickly if they dissipate excessive power.
* There is no standard pinout for the TO-92. The American
BJT
A bipolar junction transistor (BJT) is a type of transistor that uses both electrons and electron holes as charge carriers. In contrast, a unipolar transistor, such as a field-effect transistor, uses only one kind of charge carrier. A bipolar ...
s use the E-B-C pinout while their Japanese counterparts use the E-C-B pinout and some RF devices use the B-E-C pinout.
Voltage and current
Although TO-92 devices are mainly used in low-voltage / low-current (<30 V; <1 A) applications, high-voltage (600 Volt Vce) and high-current (5 A Ic) devices are available. Nominal maximum power dissipation is less than one watt (600 mW).
Variants
For diodes or integrated circuits with two connections (e.g. temperature sensors) the middle lead is either not connected or omitted entirely.
![Miniplast vs TO-92](https://upload.wikimedia.org/wikipedia/commons/d/db/Miniplast_vs_TO-92.jpg)
In the late 1960s,
Ferranti
Ferranti or Ferranti International plc was a UK electrical engineering and equipment firm that operated for over a century from 1885 until it went bankrupt in 1993. The company was once a constituent of the FTSE 100 Index.
The firm was known ...
introduced a smaller package with a compatible footprint, called "E-Line". This package was later standardized as a
British Standard
British Standards (BS) are the standards produced by the BSI Group which is incorporated under a royal charter and which is formally designated as the national standards body (NSB) for the UK. The BSI Group produces British Standards under the a ...
(but not by JEDEC) and remained in production with Ferranti Semiconductors' successor companies (
Plessey
The Plessey Company plc was a British electronics, defence and telecommunications company. It originated in 1917, growing and diversifying into electronics. It expanded after World War II by acquisition of companies and formed overseas compani ...
,
Zetex Semiconductors
Zetex Semiconductors plc is a UK-based manufacturer of discrete semiconductor devices such as diodes and transistors.
Corporate history
Originally a subsidiary of Ferranti Semiconductor, Zetex took its name from Ferranti's ZTX series of bip ...
,
Diodes Incorporated
Diodes Incorporated is a global manufacturer and supplier of application specific standard products within the discrete, logic, analog, and mixed-signal semiconductor markets. Diodes serves the consumer electronics, computing, communications, in ...
). In East Germany the E-Line package was known as the "Miniplast" package and widely used by
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 ...
.
Standards
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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—2017
, -
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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 200-8380
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, -
, TGL 11811
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, TGL 26713/07
[
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, F4
]
Common components in a TO-92 package
Common transistors:
*BC548
The BC548 is a general-purpose NPN bipolar junction transistor commonly used in European and American electronic equipment. It is notably often the first type of bipolar transistor hobbyists encounter and is often featured in designs in hobby elec ...
, general purpose NPN transistor
A bipolar junction transistor (BJT) is a type of transistor that uses both electrons and electron holes as charge carriers. In contrast, a unipolar transistor, such as a field-effect transistor, uses only one kind of charge carrier. A bipolar ...
* BC558, general purpose PNP transistor
A bipolar junction transistor (BJT) is a type of transistor that uses both electrons and electron holes as charge carriers. In contrast, a unipolar transistor, such as a field-effect transistor, uses only one kind of charge carrier. A bipolar ...
* 2N3904, general purpose NPN transistor
* 2N3906, general purpose PNP transistor
* 2N7000, N-channel FET
The field-effect transistor (FET) is a type of transistor that uses an electric field to control the flow of current in a semiconductor. FETs (JFETs or MOSFETs) are devices with three terminals: ''source'', ''gate'', and ''drain''. FETs contr ...
* BS170, N-channel FET, similar to 2N7000
*PN2222A, a "plastic" version of the original 2N2222
The 2N2222 is a common NPN bipolar junction transistor (BJT) used for general purpose low-power amplifying or switching applications. It is designed for low to medium current, low power, medium voltage, and can operate at moderately high spee ...
NPN transistor which came in a TO-18
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''.
Constructi ...
package
Other common components:
*MK484
The MK484 AM radio IC is a fully functional AM radio detector on a chip. It is constructed in a TO-92 case, resembling a small transistor. It replaces the similar ZN414 AM radio IC from the 1970s. The MK484 is favored by many hobbyists. It is ad ...
, AM radio integrated circuit
An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny ...
* 78Lxx series, voltage regulator integrated circuits
*TL431
The TL431 is a three-terminal adjustable precision shunt voltage regulator integrated circuit. With the use of an external voltage divider, a TL431 can regulate voltages ranging from 2.5 to 36 V, at currents up 100 mA. The typical initial deviati ...
, voltage regulator integrated circuit
References
External links
TO-92 Package
EESemi.com
Essay about TO92 housings (German) by Dipl.-Ing. Bernd Wiebus at German national library server.
{{DEFAULTSORT:TO-092
Semiconductor packages