2N3055

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. Its numbering follows the JEDEC standard. It is a transistor type of enduring popularity.

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

Specifications

The exact performance characteristics depend on the manufacturer.

manufacturer	Vce	Ic	PD	hfe	fT
ON-Semiconductor	100V	15A	115W	20-70	3.0 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). 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.

File:PowerTransistor 2N3055 1.jpg

2N3055 transistor internals.

History

File:Toshiba 2n3055 transistor.jpg

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. 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. 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. 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.

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. 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 in a push–pull output configuration.

Related devices

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 is a complementary (PNP) transistor for the 2N3055, which is also manufactured using the epitaxial process today. A TO-3 P version of the 2N3055 and its complementary device MJ2955 are available as respectively TIP3055 and TIP2955. 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). Transistors TIP33 and 34 are respectively NPN and PNP transistors presenting similar characteristics as the 2N3055 and MJ2955.

File:Tesla KD503 transistor.jpg

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. 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	80V	20A	150W	80	2.0 MHz

Further reading

• Datasheets from ST and ON
• Datasheet KD503 Datasheetcatalog