2N2222

The 2N2222 is a widely used NPN bipolar junction transistor (BJT) designed for general-purpose amplification and switching. It is commonly packaged in the TO-92 through-hole form, and is also available in surface-mount variants such as MMBT2222A. The device is one of the most familiar small-signal transistors used in hobbyist and professional electronics.

Typical specifications vary by manufacturer, but common ratings include a collector-emitter voltage Vceo of about 30 to 40 volts and a maximum collector current Ic of around 600 mA. The DC current gain hFE is typically in the hundreds, roughly 100–300 at moderate Ic, and the transition frequency fT is in the hundreds of megahertz, reflecting suitability for both amplification and switching at relatively high speeds. Power dissipation depends on packaging and cooling, but is limited to a few hundred milliwatts in the TO-92 package.

The standard through-hole pinout for the TO-92 version, with the flat face toward the viewer and leads downward, is emitter-base-collector (E-B-C) from left to right; pinouts can vary in different packages or manufacturers, so consulting the datasheet is advised.

Common uses include low-power signal amplification, small-signal switching, and buffering in hobby projects and consumer electronics. The 2N2222 is frequently cross-referenced with the PN2222 family and with the 2N2222A variant, which offers similar characteristics with some improvements in breakdown voltage and gain. Availability in both through-hole and surface-mount formats supports its widespread use in education and design prototyping.