2N2222

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2N2222A (TO-18 package) with Emitter, Base and Collector identified as "e" "b" "c" respectively.

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 speeds. It is made in the TO-18 metal can as shown in the picture.

Replacements are commonly available now in the cheaper TO-92 packaging, where it is known as the PN2222 or P2N2222, which has similar specifications except for the lower maximum collector current.[1] However, one should be aware that the P2N2222 — note the ″2″ between the ″P″ and ″N″ — is not pin-compatible with the PN2222 and has its emitter and collector connections switched.

Single transistors are also available in several different surface mount packages, and a number of manufacturers market surface mount packages that incorporate several 2N2222 transistors in one package as an array of transistors. The general specifications of the various variants are similar, with the biggest difference being the maximum allowable current and power dissipation.

The 2N2222 is considered a very common transistor,[2][3][4] and is used as an exemplar of an NPN transistor. It is frequently used as a small-signal transistor,[5][6] and it remains a small general purpose transistor[7] of enduring popularity.[8][9][10]

The 2N2222 was part of a family of devices described by Motorola at a 1962 IRE convention.[11] Since then it has been made by many semiconductor companies, for example, Texas Instruments.[12]

Specifications[edit]

The JEDEC registration of a device number ensures particular rated values will be met by all parts offered under that number. JEDEC registered parameters include outline dimensions, small-signal current gain, transition frequency, maximum values for voltage withstand, current rating, power dissipation and temperature rating, and others, measured under standard test conditions. Other part numbers will have different parameters. The exact specifications depend on the manufacturer, case type, and variation. Therefore it is important to refer to the datasheet for the exact part number and manufacturer.

Manufacturer Vce Ic PD fT
ST Microelectronics[13]
2N2222A
40 V 800 mA 500 mW/1.8 W 300 MHz

All variations have a beta or current gain (hFE) of at least 100 in optimal conditions. It is used in a variety of analog amplification and switching applications.

NPN silicon transistors with similar properties are also made in a variety of small through-hole and surface mount packages including TO-92, SOT-23, and SOT-223.

Package Variants and Pinout Confusion[edit]

As mentioned above, the 2N2222 transistor is available from many manufacturers and in a variety of packages. There exists some confusion regarding the pinout for TO-92 packages. One manufacturer markets the P2N2222 transistor — note the ″2″ between the ″P″ and ″N″ , which has a different pinout from the much more common PN2222, the difference being that the emitter and collector are switched. Incidentally, this manufacturer markets both a PN2222 (common pinout) and P2N2222 (switched pinout). When the emitter and collector of a BJT is interchanged, the resulting component is still a BJT but it has significantly reduced current gain. Consequently, some electronic circuits will not work, or work with diminished performance. Somewhat surprisingly, there are many circuits that will work quite well if one were to use a BJT with the collector and emitter switched. This is because the vast majority of electronic circuits use some sort of negative feedback and one of the advantages of negative feedback is that, if used properly, it makes the circuit performance very independent from circuit components' performance.

Related transistors[edit]

The BC548 is a low voltage, low current; general-purpose switching transistor in a TO-92 package.

The 2N2907 is an equally popular (PNP) transistor complementary to the 2N2222.[14]

The 2N3904 is an NPN transistor that can only switch one-third the current of the 2N2222 but has otherwise similar characteristics. The 2N3904 exhibits its forward gain (beta) peak at a lower current than the 2N2222, and is useful in amplifier applications with reduced Ic, e.g., (gain peak at 10 mA for the 2N3904 but 150 mA for the 2N2222).

The 2N2219 is very similar with higher power dissipation rating.

References[edit]

  1. ^ http://www.fairchildsemi.com/ds/PN/PN2222.pdf Retrieved 3rd June 2012
  2. ^ Dan O'Sullivan, Tom Igoe; "Physical Computing"; Cengage Learning; pp.19; 2004; ISBN 1-59200-346-X
  3. ^ Brad Graham, Kathy McGowan; "Mind Performance Projects for the Evil Genius"; McGraw Hill Professional; pp.18; 2010; ISBN 978-0-07-162392-6
  4. ^ Brad Graham, Kathy McGowan; "51 High-Tech Practical Jokes for the Evil Genius"; McGraw Hill Professional; pp.12; 2007; ISBN 978-0-07-149494-6
  5. ^ Gordon McComb; "The Robot Builder's Bonanza"; McGraw-Hill Professional; 2001; pp.261; ISBN 978-0-07-136296-2
  6. ^ William Rynone; "Linear Active Circuits — Design and Analysis"; Artech House; pp.19; 1986; ISBN 0-89006-199-8
  7. ^ Dennis Barnaal, "Analog and Digital Electronics for Scientific Application"; Breton Publishers; pp.301; 1982; ISBN 0-534-01044-X
  8. ^ Rudolf F. Graf and William Sheets (2001). Build your own low-power transmitters: projects for the electronics experimenter. Newnes. p. 14. ISBN 978-0-7506-7244-3. "The 2N2222, 2N2905, and 2N3055 devices, for example, which date back to the 1960s but have been improved, are still useful in new designs and are still popular for experimenters." 
  9. ^ Ed Da Silva (2001). High frequency and microwave engineering. Newnes. p. 263. ISBN 978-0-7506-5046-5. "Typical examples are the well known NPN and PNP industrial and military types, 2N2222 and 2N2907, which have been used for over four decades and are still being used in many designs." 
  10. ^ Jack Ward. "THE DEVELOPMENT OF THE 2N2222: The Most Successful and Widely Used Transistor Ever Developed!". The Transistor Museum. Archived from the original on 14 April 2011. Retrieved 26 March 2011. "Since its initial product launch by Motorola at the 1962 IRE Convention, the 2N2222 has become the most widely used and universally recognized transistor of all time. Billions of units have been manufactured over the past 45 years and there is continuing high volume annual production." 
  11. ^ http://www.semiconductormuseum.com/Transistors/Motorola/Haenichen/Haenichen_Page11.htm Haenichen oral history retrieved from the Semiconductor Museum 2011 May 13
  12. ^ The Transistor and Diode Data Book for Design Engineers, Texas Instruments Incorporated, no date, TI publication number CC413 71242-73-CSS, page 4-93
  13. ^ http://www.st.com/st-web-ui/static/active/en/resource/technical/document/datasheet/CD00003223.pdf Datasheet accessed 2013-10-26
  14. ^ Dave Hrynkiw and Mark W. Tilden (2002). Junkbots, bugbots, and bots on wheels: building simple robots with BEAM technology. McGraw-Hill Professional. p. 44. ISBN 978-0-07-222601-0. "Learn to keep an eye open for the following transistors, as they're among the most useful, inexpensive, and popular types: PN2222/PN2907 These are general-purpose NPN/PNP transistors that can drive some good amounts of power. They're listed together because they're complementary transistors." 

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