2N3055

The 2N3055 is a silicon NPN power transistor intended for general purpose applications. It was introduced in the early 1960s by RCA using their "hometaxial" power transistor process. Its numbering follows the JEDEC standard. It is a transistor type of enduring popularity.

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	Vcbe	Ic	PD	hfe	fT
ON-Semiconductor	60V	15A	115W	20-70	2.5MHz

Packaged in a TO-3 case style, it is a 15 amp, 60 volt, 115 watt power transistor with a β (forward current gain) of 20 to 70 at a collector current of 4 A. It can provide gain at frequencies up to 2.5 MHz.

History

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. 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, now bearing the designator 2N3055, 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 remains 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.

Hobby uses

The 2N3055 is also popular amongst hobbyists experimenting with high voltage transformers. The horizontal output transformer from a CRT type TV can be driven using just two resistors and a 2N3055 in flyback mode, transforming a low voltage, such as 12 volts, into several kilovolts. The output is very low current, so there is a minimal chance of dangerous electric shock. However, the design is limited by the 2N3055's ability to handle this sort of circuit, and will overheat and quickly fail from the inductive voltage feedback spikes from the transformer. Hobbyists would, after gaining an understanding of high voltage, then move on to higher power circuits and transformers. This transistor must be counted among the hobbyists as the most used power transistor, after being used in audio power amplifier with powers ranging from 10W to 400W.

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.