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2N3055 Power Transistor, 2N3055 Datasheet PDF, Circuit Schematic, Pinouts

2n3055 Transistor: Datasheet PDF and Circuit Schematic

The 2N3055 power transist is a silicon NPN transistor intended for general purpose applications.

2N3055 transistor datasheet for download 2n3055 power transistor

2N3055 Price Check

2N3055 Power Transistor Technical Specifications

The 2N3055 transistor is a silicon NPN power transistor intended for general purpose applications. It was introduced in the early 1960's by RCA using their "hometaxial" power transistor process. It was one of the first silicon power transistors, offered unrivalled second breakdown immunity and found many applications particularly in audio power amplifiers and linear power supplies.

The exact specs depend on the manufacture, it is important to reference the datasheet for the exact device and brand you are dealing with.

Packaged in a TO3 can, it is a 15A amp, 60V volt, 115W watt power transistor with a Beta of 20 to 70 at a collector current of 4A. It gained popularity because it had 100 % safe-operating-area, (SOA), meaning that it could dissipate 115W at a collector voltage of 60V (Ic=1.9A), provided the case temperature did not exceed 25 deg.C. It 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 slow (typically the unity-gain frequency was 1 MHz) The 2N3055 power transistor was the first multi-amp silicon transistor to sell for less than one dollar! It was a huge success in the power supply market..

With changes to the technology, the original process became uneconomical and a similar device, now using the name 2N3055 transistor, was supplied using epitaxial base technology. The maximum voltage and current ratings of this device are the same as the original, but 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, so allowing the newer type of 2N3055 transistor to be more efficient in switching power supplies. Also the higher frequency response improves the performance when used in audio amplifiers. Some suppliers offer a high safe-operating-area version of the 2N3055 power transistor using the "H" suffix.

The 2N3054 transistor is a lower power version of the 2N3055 transistor, rated at 25W, 55V and 4A, but became almost obsolete about the late 1980's 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 power transistor applications. An MJ2955 is a complementary (PNP) transistor for the 2N3055 transistor, which is also manufactured using the epitaxial process today.


2n3055 Transistor Pinouts and Picture

2n3055 circuit schematic 2n3055 picture


2n3055 Power Transistor Sources

The 2N3055 transistor is widely available from a variety of sources from Radio Shack to Allied Electronics. Prices range from $0.99 to $2.00.


Project: Ignition Coil Driver with 2N3055 Transistor and 555 IC

Here is a very simple circuit that will provide high voltage (15-40kV) sparks using a common ignition coil. The input is 12VDC at around 5 to 6 amps. Mine produces sparks that are about 3/4" to 1" in length. A 2N3055 power transistor is pulsed with a square wave signal that comes from the 555 IC Timer. The frequency of the pulses depends on the resistors between pins 7 and 8 and between pins 7 and 6. The pulse is also dependent on the capacitor. You can experiment with these values. Try inserting a smaller capacitor to raise the frequency. At different frequencies the sparks will change certain characteristics. At a high frequency the sparks will get fatter but shorter in length. At lower frequencies the spark maybe longer but thinner. I assembled my project on a solderless breadboard. You can use whatever you like. The capacitor should be a tantalum or mylar type, but this is not absolutely necessary. A ceramic type should work fine just as long as the temperature is not too high around it.  Read more:

555 Timer IC, 2n3055 Ignition Coil Driver


Project: 100 Watt Inverter Circuit with the 2N3055


Here is a 100 Watt inverter circuit using minimum number of components.I think it is quite difficult to make a decent one like this with further less components.Here we use CD 4047 IC from Texas Instruments for generating the 100 Hz pulses and four 2N3055 transistors for driving the load.

The IC1 Cd4047 wired as an astable multivibrator produces two 180 degree out of phase 100 Hz pulse trains.These pulse trains are are preamplifes by the two TIP122 transistors.The out puts of the TIP 122 transistors are amplified by four 2N 3055 transistors (two transistors for each half cycle) to drive the inverter transformer.The 220V AC will be available at the secondary of the transformer.Nothing complex just the elementary inverter principle and the circuit works great for small loads like a few bulbs or fans.If you need just a low cost inverter in the region of 100 W,then this is the best.

Circuit Diagram with Parts List.



  • A 12 V car battery can be used as the 12V source.
  • Use the POT R1 to set the output frequency to50Hz.
  • For the transformer get a 9-0-9 V , 10A step down transformer.But here the 9-0-9 V winding will be the primary and 220V winding will be the secondary.
  • If you could not get a 10A rated transformer , don’t worry a 5A one will be just enough. But the allowed out put power will be reduced to 60W.
  • Use a 10 A fuse in series with the battery as shown in circuit.
  • Mount the IC on an IC holder.
  • Remember,this circuit is nothing when compared to advanced PWM inverters.This is a low cost circuit meant for low scale applications.

Design Tips.

The maximum allowed output power of an inverter depends on two factors.The maximum current rating of the transformer primary and the current rating of the driving transistors.

For example ,to get a 100 Watt output using 12 V car battery the primary current will be ~8A ,(100/12) because P=VxI.So the primary of transformer must be rated above 8A.

Source: Circuits Today

Also here ,each final driver transistors must be rated above 4A. Here two will be conducting parallel in each half cycle, so I=8/2 = 4A .

These are only rough calculations and enough for this circuit.


Project: Simple 60 Watt Power Amplifier with 2N3055 Transistor

The first version of the amp shown here uses a single power supply and capacitor coupled speaker. It also uses quasi-complementary symmetry for the output stage. Note the really sneaky way the Class-A driver amp's collector load is bootstrapped !

Quasi-complementary symmetry was a scheme used in the days when PNP power transistors were expensive and useless. If you wanted any sort of voltage and current rating, you had to use NPN devices. The quasi-complementary output stage used a (discrete) Darlington for the positive side, and a complementary pair for the negative (i.e. a PNP driver coupled to an NPN power transistor).

Almost all amps of the era from which this circuit originated used the 2N3055 power transistor - this was the pre-eminent power transistor (NPN of course), and there were no vaguely equivalent PNP devices for less than about 5 times the price, and even these were highly inferior. As a result, the quasi-complementary output was very common, until decent PNP power devices became more readily available. Immediately, just about everyone started using NPN and PNP Darlington coupled devices for the output stages (as shown for Q3 and Q4) - the funny part is that it was demonstrated back in the mid 1970's that the full Darlington connection actually sounds (or at least measures) worse than quasi-complementary stages. Read full details:

2n3055 60W Power Amplifier


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