The PN2222A, also known as the PN2222, is a general-purpose transistor best suited to applications that don’t require high stress on the component. Depending on the datasheet, it is characterized as a transistor or an amplifier, but it can perform both of those functions. The PN2222A is equivalent to the 2N2222A, and the names are often used interchangeably among the electronics community. There are many transistors with different names that are almost functionally identical to the PN2222A.
Like most transistors, the PN2222A can function as a transistor, switch, or amplifier. It is an NPN type transistor with an operating temperature range of -55 to 150 degrees Celsius. The component can dissipate 625 mW of power, giving it good thermal control for not being a MOSFET, which is designed for thermal dissipation. It has an extremely low switching delay time of 10 nanoseconds, potentially as low as 5 nanoseconds, which has likely contributed to its continued popularity. The PN2222A is commonly called a small signal transistor due to its low energy applications. Its PNP complementary type, which can function similarly, is PN2907A. Taking into account NPN variations, PNP complementary types, and transistors that function similarly, this overview can be applied to more than a dozen transistors.
The PN2222A can be structured differently from the traditional transistor “jellyfish” shape, where three prongs extend downward from a solid base. Alternative structures have dramatically shorter prongs than normal transistors. One structure can place the base and emitter prongs on one side of a large rectangular base with the collector prong on the other. Another structure places the base, collector, and emitter prongs all on one side of the large rectangular base with a fourth, larger collector prong on the opposing side. These structures are more compact than a usual transistor and can save space in electronics projects.
The PN222A is suitable for televisions, consumer electronics, home appliances, and robotics. It has been commonly used in Arduino projects for more than a decade and can be paired with more robust transistors like MOSFETs. Complex projects for the Internet of Things (IoT) can also make use of the PN2222A. This last use is of particular interest, since it allows amateur electronics engineers to conceptualize IoT projects and democratize electronics development.
PN2222A Special Considerations
The PN2222A is not suited for applications that require extremely high operating temperatures or voltages, although it can handle high current loads. It is also important that designers not stress the PN2222A to its maximum ratings for an extended period of time. The PN2222A can switch between high current loads up to 800 mA, which distinguishes it from similar transistors. Different datasheets say that this current load could be significantly smaller, but compared to other transistors, the PN2222A always handles high current loads. The BC547 is similar to the PN2222A, but cannot handle the same high current loads. When choosing between the PN2222A and similar transistors, designers should be careful to choose one that can handle the current load their project requires. This is especially important when combining the PN2222A with another transistor to create a Darlington pair, which amplifies current through one transistor, then another, creating potentially greater current levels than one transistor could handle alone.
Many different companies have created variants of the PN2222A, resulting in many datasheets detailing components with slightly different properties. Designers should make sure, when referencing a datasheet, to use the most recently available sheet that corresponds to the company that made their specific PN2222A. Current tolerances can vary significantly between companies, even though the component itself is specialized for higher current loads.
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