2N3055 Datasheet: Transistor Built For Power Supply Designs

Today, diodes or metal-oxide-semiconductor field-effect transistors (MOSFETs), often come to mind when considering switching components for PCB design. For either very simple or very complex circuits, these may indeed be the best choice. However, for power supply operation circuits, a bipolar junction transistor (BJT), as defined in the 2N3055 datasheet, may be the better option.

2N3055 BJT: Features and Applications

BJT were the first transistors, having been around since 1947. Although simple, these components exhibit all the characteristics that have enabled transistors to revolutionize electronics and drive many of technological innovations we enjoy today. The 2N3055 by Onsemi, which has the features listed below, is a commonly utilized member of this group.



Importance Level

Reliable, safe area operation


RoHS compliant

High (some markets, like the EU, all electronic parts adhere to RoHS regulations)

20 – 70 collector current gain range


Metal case construction

High (for hazardous environment operation)

Simple design


The features above, specifically safe operation and metal case construction, make the 2N3055 a good choice for power supply designs, in addition to general switching and amplifier applications.

2N3055 BJT: Important Specifications

The 2N3055 datasheet includes important information to inform your choice of this transistor for your electronic circuit design. For example, the following maximum ratings must be adhered to for reliable operation.

2N3055 maximum ratings.

2N3055 maximum ratings.

Additionally, you should familiarize yourself with the thermal and electrical characteristics of the device, which are shown below.

2N3055 thermal and electrical characteristics

Thermal and electrical characteristics of the 2N3055 BJT.

2N3055 BJT: Operational Characteristics

The 2N3055 is a NPN BJT. Onsemi offers a PNP complimentary transistor, the MJ2955. As shown in the 2N3055 datasheet, these transistors have the following saturation characteristics.

2N3055 and MJ2955 saturation current curves.

2N3055 and MJ2955 saturation current curves.

As shown above, the characteristics are nearly identical for collector currents of 1.0 A. However, the variation grows as the collector current increases. Below, the characteristics curves for normal “ON” operation are shown.

2N3055 and MJ2955 ON operation curves.

2N3055 and MJ2955 ON operation curves.

Below, the DC gain (Ic/Ib) curves are illustrated. As indicated, the MJ2955–PNP configuration–typically exhibits a higher gain over the ranges of operation shown.

DC gain curves for the 2N3055 and MJ2955.

DC gain curves for the 2N3055 and MJ2955.

PCB Design With the 2N3055 Datasheet

In addition to the operational characteristics above, the 2N3055 datasheet also provides information for your PCB layout design. This includes space requirements for both 2D–the board surface–and 3D–height, which is important for enclosure or ECAD/MCAD integration.

2N3055 PCB layout dimensions

PCB layout dimensions for 2N3055 BJT.

As shown above, this component package is used for a number of component types. This information is critical to ensure the accuracy of etching during board fabrication and component placement during PCB assembly. This data could also be used to aid you in creating the schematic symbol and footprint. This not advisable.

Virtually all EDA software programs include functionality for building component libraries, which include symbols and footprints. However, doing so comes with substantial risk. Errors in the footprint can render your design unbuildable due to pin-pad mismatch, trace-pad misalignment, or component-pad size discrepancies. Any of these errors will likely require redesign and/or respin resulting in delayed development and unnecessary, additional costs. A better alternative is to source your component CAD models from a trusted resource, as shown below.

2N3055 schematic symbol and board footprint from UL

CAD models for the 2N3055 from UL.

By leveraging the important data and information of the 2N3055 datasheet and relying on dependable manufacturer-vetted CAD models, you can optimize your PCB design with this BJT.

If you’re looking for CAD models for common components or important information on how to best use the 2N3055 datasheet for your PCB design, Ultra Librarian helps by compiling all your sourcing and CAD information in one place.

Working with Ultra Librarian sets up your team for success to ensure streamlined and error-free design, production, and sourcing. Register today for free.


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