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The 2N3055 is a silicon NPN power
Power semiconductor device
Power semiconductor devices are semiconductor devices used as switches or rectifiers in power electronic circuits . They are also called power devices or when used in integrated circuits, called power ICs....

A transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current...

 intended for general purpose applications.
It was introduced in the early 1960s by RCA using a hometaxial power transistor process, transitioned to an epitaxial
Epitaxy refers to the deposition of a crystalline overlayer on a crystalline substrate, where the overlayer is in registry with the substrate. In other words, there must be one or more preferred orientations of the overlayer with respect to the substrate for this to be termed epitaxial growth. The...

 base in the mid 1970s. Its numbering follows the JEDEC
The JEDEC Solid State Technology Association, formerly known as the Joint Electron Devices Engineering Council , is an independent semiconductor engineering trade organization and standardization body...

 standard. It is a transistor type of enduring popularity.


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
The ampere , often shortened to amp, is the SI unit of electric current and is one of the seven SI base units. It is named after André-Marie Ampère , French mathematician and physicist, considered the father of electrodynamics...

, 60 volt
The volt is the SI derived unit for electric potential, electric potential difference, and electromotive force. The volt is named in honor of the Italian physicist Alessandro Volta , who invented the voltaic pile, possibly the first chemical battery.- Definition :A single volt is defined as the...

, 115 watt
The watt is a derived unit of power in the International System of Units , named after the Scottish engineer James Watt . The unit, defined as one joule per second, measures the rate of energy conversion.-Definition:...

 power transistor with a β (forward current gain) of 20 to 70 at a collector current of . It has a transition frequency of 2.5 MHz; at this frequency the calculated current gain (beta) drops to 1, indicating the transistor can no longer provide useful amplification.


The 2N3055 was designed for medium-current
Electric current
Electric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...

 and high-power
Electric power
Electric power is the rate at which electric energy is transferred by an electric circuit. The SI unit of power is the watt.-Circuits:Electric power, like mechanical power, is represented by the letter P in electrical equations...

 circuits. Commercially, it was used in many linear power supplies, audio amplifiers and low frequency power converters. It was second sourced
Second source
In the electronics industry, a second source is a company that is licensed to manufacture and sell components originally designed by another company ....

 by other manufacturers; Texas Instruments
Texas Instruments
Texas Instruments Inc. , widely known as TI, is an American company based in Dallas, Texas, United States, which develops and commercializes semiconductor and computer technology...

 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
Epitaxy refers to the deposition of a crystalline overlayer on a crystalline substrate, where the overlayer is in registry with the substrate. In other words, there must be one or more preferred orientations of the overlayer with respect to the substrate for this to be termed epitaxial growth. The...

 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 into an 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
Flyback transformer
A flyback transformer , also called a line output transformer , is a special transformer, which is used for conversion of energy in electronic circuits. It was initially designed to generate high current sawtooth signals at a relatively high frequency...

 from a CRT
Cathode ray tube
The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...

 type TV can be driven using just two resistors and a 2N3055 in flyback mode
Flyback converter
The flyback converter is used in both AC/DC and DC/DC conversion with galvanic isolation between the input and any outputs. More precisely, the flyback converter is a buck-boost converter with the inductor split to form a transformer, so that the voltage ratios are multiplied with an additional...

, 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
Voltage spike
In electrical engineering, spikes are fast, short duration electrical transients in voltage , current , or transferred energy in an electrical circuit....

 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 , and , 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.