Transistor 2N3055: Pinout, Equivalent and Specs

In this text we will discuss the specifications of the 2N3055 bipolar NPN transistor, its pinout, and the replacement equivalents. It is manufactured using epitaxial basic process, in hermetically sealed metal package TO-3. The device is designed to work in switching circuits and power amplifiers.


The 2n3055 pinout is made in a metal TO-3 package with glass insulators, through which the base (B) and emitter (E) pins are brought outside. The collector pin (C) is physically connected to the case. The details are shown below.


The transistor body and the connecting bolts are insulated, when mounted on a heat sink, through a special mica or ceramic substrate.

Historical reference

The history of this popular semiconductor device is well known. It was originally developed in the 60’s by RCA (engineers from Herb Meisel’s group) and was manufactured using the mesa-planar process. It was designed to work in power amplifiers. Later it was used in regulators and voltage regulators in power supplies. Since the mid 70’s, together with the search for a more economical way of production, it began to be made by epitaxial technology. Not bad amplifying properties, their linearity at the same time, made the device an indispensable companion to many LCFs of that time.

Unfortunately, RCA ceased to exist in 1988. Its semiconductor business was acquired by the American Harris Corporation. Now many foreign companies produce transistors labeled 2N 3055, including those using environmentally friendly lead-free (Pb-Free) standards. It is believed that newer copies (produced by epitaxial technology) work better in amplification circuits, but are less protected against high voltages.

However, recently the quality of manufacturing of such transistors has fallen dramatically, especially with the appearance of Chinese competitors. In addition, there are cases of counterfeit transistors. It is unlikely to buy an original copy on Internet sites like Aliexpress, Amazon, eBay, etc. Therefore, many radio amateurs prefer its older versions produced mainly before 2000.



The 2N3055 is a low-frequency transistor. At the same time, it is believed that the typical boundary frequency of its transition is in the range of 3-6 MHz. But this was not always the case. This parameter first appeared in 1971 in RCA’s data sheets and was only 0.8 MHz. Gradually it grew, along with the improvement of the technical manufacturing process. In 1977, it reached its present value of 2.5 MHz.

The basic parameters of the transistor in question, since the beginning of its production (since 1967), have not changed much. They may differ slightly from manufacturer to manufacturer.

Maximum specifications of the 2N3055:

  • K-B voltage limit (VCBO max) up to 100 V, with open circuit E;
  • K-E voltage limit (VCEO max) up to 70 V, with open circuit to B;
  • maximum collector current (IC max) up to 15 A;
  • power dissipation (RC max) up to 115 W;
  • Static current transfer coefficient (HFE) 20 … 70;
  • Transition temperature (TC) up to 200 oC, storage temperature (Tstg) -65 … +200 oC.

Exceeding any of these values may result in device failure. As the ambient temperature rises, the power dissipation drops linearly.


Аs a replacement you can use modern options with higher voltage rating 2N3055HV (VCEO = 100V), MJ15015G (VCEO = 120V). A good alternative is T2N6371HV. It is worth to pay attention to the currently available variants in a plastic package TO-3PN type TIP3055 up to 90W. The most popular Russian equivalent of 2N3055 is a powerful bipolar transistor KT819GM from JSC “Group KREMNY EL”.

In the 70’s Philips produced very similar devices marked BDY20 (VCEO up to 60V) and positioned them for use in Hi-Fi equipment. KD502, KD503 of the former Czechoslovak manufacturer Tesla are still considered by radio amateurs to be very reliable and quality equivalents. Unfortunately it is very difficult to find them now, because they are no longer in production, and the company fell into decline after the collapse of the Soviet Union.

The complementary pair

The device has a complementary pair MJ2955 with a PNP junction. In terms of its parameters, except for the silicon structure, it is almost a complete copy of the 2N3055 transistor. It is used in combination with it in output stages of high-power amplifiers up to 40 W at load up to 8 Ohm, and 60 W at 4 Ohm.


The most common products are from the following manufacturers: Inchange, ON Semiconductor, STMicroelectronics. You can download a datasheet for the device by following the link with the company name.

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