The 2n2222a transistor is a bipolar junction transistor (BJT) consisting of three terminals, and composed of a semiconductor material. Used for low power amplifying and switching, it comes in both common surface mount and through hole packages for placement on circuit boards This transistor is the most used of all the types of transistors and was first developed in the early 1960s. It is a variation of the BJT transistor called a negative-positive-negative (NPN,) consisting of a transistor base of P-doped semiconductor, which amplifies the incoming current, in between two separate N-doped layers designed to transport the conducted energy.
Components of the 2n2222a transistor, arranged into a three prong format, include the base lead, as well as a positive collector and negative emitter. These elements can be seen in a transistor schematic with the base, emitter, and collector sides appropriately labeled. A circular pattern in the center shows where each lead comes together inside the transistor. The individual 2n2222a transistor layout can be seen in a schematic of a transmitter as well to understand the design and how components are arranged in a functional electronic system.
A manufacturing capability called the annular process was begun in the late 1950s and the star geometry transistor was created at that time. It preceded the development of the 2n2222 series transistors which were based on that kind of geometry, designed by a major electronics development and manufacturing company. The unit is available in a metal case style that is standard for other types of transistors as well. Several major electronics manufacturers integrate the 2n2222a transistor into electronics such as transistor radios.
Transistor characteristics can support low to medium levels of current. The 2n2222a transistor can also tolerate high speed operation, and functions at medium voltage and low power. Current levels up to 500 milliamperes are tolerated by the collector of the transistor, while leakage currents along with saturation voltage are kept low. Lower voltage variations have become available in the early 21st century, including a transistor to complement the use of the 2n2222a transistor and other types that switch a fraction of the current but are suitable for low power devices.
This works well in many different applications, so is used by many manufacturers to build electronics that operate with low level signals. Frequency modulation (FM) transmitters and shortwave radios also contain this kind of transistor. A 2n2222a transistor can be found in many types of electronics, even though similar components have become outdated as new technologies are regularly developed.