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The 2N3055 is a silicon NPN power transistor intended for general purpose applications. It was introduced in the early 1960s by RCA using a hometaxial power transistor process, transitioned to an epitaxial base in the mid-1970s.[1] Its numbering follows the JEDEC standard.[2] It is a transistor type of enduring popularity.[3][4][5]

2N3055 transistor mounted on an aluminum heat sink. A mica insulator electrically isolates the transistor case from the heatsink.


The exact performance characteristics depend on the manufacturer.

manufacturer Vce Ic PD hfe fT
ON-Semiconductor[6] 60V 15A 115W 20-70 2.5 MHz

Packaged in a TO-3 case style, it is a 15 amp, 100 volt, 115 watt power transistor with a β (forward current gain) of 20 to 70 at a collector current of 4 A (100 to 200 when testing using a multimeter[6]). It has a transition frequency of 3.0 MHz; at this frequency the calculated current gain (beta) drops to 1, indicating the transistor can no longer provide useful amplification in common emitter configuration.

2N3055 transistor internals.


2N3055 transistors have several applications in power circuits, including inverters and voltage regulators.

The 2N3055 was designed for medium-current and high-power circuits. Commercially, it was used in many linear power supplies, audio amplifiers and low frequency power converters. It was second sourced by other manufacturers; Texas Instruments listed a single-diffused mesa version of the device in an August 1967 datasheet.[7] One limitation was that its frequency response was rather low (typically the unity-gain frequency was 1 MHz).

With changes to semiconductor manufacturing technology, the original process became economically uncompetitive in the mid-1970s, and a similar device was created using epitaxial base technology.[1] The maximum voltage and current ratings of this device are the same as the original, but it is not as immune from secondary breakdown; the power handling (safe operating area) is limited at high voltage to a lower current than the original.[1] However, the cut-off frequency is higher, allowing the newer type of 2N3055 to be more efficient at higher frequencies. Also the higher frequency response has improved performance when used in audio amplifiers.[1]

Although the original 2N3055 went into decline relative to epitaxial-base transistors because of high manufacturing costs, the epitaxial-base version continued to be used in both linear amplifiers and switching supplies.[1] Several versions of the 2N3055 remain in production; it is used in audio power amplifiers delivering up to 40 W into an 8 ohm load[8] in a push–pull output configuration.

Related devices[edit]

The 2N3054 is a lower power version of the 2N3055, rated at 25 W, 55 V and 4 A, but became almost obsolete about the late 1980s when many TO-66 devices were withdrawn from mainstream manufacturers's lists. In many cases a TO-220 packaged version, such as MJE3055T, can be used instead of the 2N3054 as well as in some 2N3055 applications. An MJ2955 (PNP), which is also manufactured using the epitaxial process today, is a complementary transistor to the 2N3055. A TO-3 P (plastic case) version of the 2N3055 and its complementary device MJ2955 are available as the TIP3055 and TIP2955 respectively. In the sixties and early seventies, Philips produced similar devices encapsulated in TO-3 packages under the reference BDY20 and BDY38 (although the BDY38 has lower voltage ratings than the 2N3055). TIP33 (NPN) and 34 (NPN) are plastic cased transistors with similar characteristics to the 2N3055 and MJ2955 respectively.

A Tesla KD503 transistor

KD503 is a higher power equivalent used in Eastern Bloc countries, and is intended for general purpose applications. It was produced exclusively by the Czechoslovakian electronics company Tesla. KD503 are packaged in a TO-3 case style (called T41 by Tesla), it is a 20 amp, 80 volt, 150 watt power transistor. It has a transition frequency of 2.0 MHz;. The KD503 have higher power and higher current than 2n3055.[9] They were used extensively in the former Eastern Bloc countries in audio power amplifiers made by Czechoslovakian Tesla, Polish Unitra.

KD503 specifications
manufacturer Vce Ic PD hfe fT
Tesla[10] 80V 20A 150W 80 2.0 MHz


  1. ^ a b c d e Ellis, J.N.; Osadchy, V.S.; Zarlink Semiconductor (November 2001). "The 2N3055: a case history". IEEE Transactions on Electron Devices. 48 (11): 2477–2484. doi:10.1109/16.960371. 
  2. ^ S M Dhir (1999), Electronic Components and Materials, Tata McGraw-Hill Education, ISBN 978-0-07-463082-2 
  3. ^ P. Horowitz; W. Hill (2001). The art of electronics (2nd ed.). Cambridge University Press. p. 321. ISBN 978-0-521-37095-0. the ever-popular 2N3055 
  4. ^ Gordon McComb (2001). The robot builder's bonanza (2nd ed.). McGraw-Hill Professional. p. 261. ISBN 978-0-07-136296-2. For high-power jobs, the NPN transistor that's almost universally used is the 2N3055 
  5. ^ Rudolf F. Graf; 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. 
  6. ^ a b "2N3055(NPN), MJ2955(PNP): Complementary Silicon Power Transistors (6th revision)" (PDF). On Semiconductor. Semiconductor Components Industries, LLC. December 2005. Retrieved 2011-03-25. 
  7. ^ The Power Semiconductor Data Book for Design Engineers First Edition, Texas Instruments Incorporated, publication no. CC-404 70977-22-IS, no date, page 5-75
  8. ^ IOSS Group (2008). IOSS Applications Electronic Audio Circuits Sourcebook. 1. p. 52–53. ISBN 1-4404-7195-9. Retrieved 2011-03-25. 
  9. ^ http://www.st.com/web/en/resource/technical/document/datasheet/CD00000895.pdf
  10. ^ "Tesla transistors:Tesla transistors datasheet". Tesla Transistors. Tesla. 1980. Retrieved 2015-12-15. 

Further reading[edit]