Why the 2N2222 Transistor Won: When a Part Becomes Infrastructure

Education
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The 2N2222 was unquestionably the correct transistor at the correct time. Designed and released in 1962, it was one of the first silicon transistors with so many desirable features. The robust high-speed switching characteristics also provided a transistor with excellent practical value for DC coupled circuits to high-speed amplifier circuits.

The 2N2222 is popular because it is a balanced device with attributes suitable for a wide range of projects. The 2N2222 and variants feature:

  • High gain typically specified as greater than 100.

  • High frequency amplification with operation into the UHF regions up to about 300 MHz.

  • Relatively high power dissipation of 1.8 W (case at 25˚ C) or 0.5 W (25˚ C ambient).

  • The TO-18 package was physically small. It offered a degree of electromagnetic shielding and facilitated additional heatsink capabilities using a small metal spreader. Surprisingly, DigiKey still has a few purpose-built TO-18 heatsinks in stock.

  • Relatively high collector current of approximately 500 mA for moderate-power applications.

  • Relatively high collector to emitter voltage (30 VDC).

  • The device was registered with JEDEC. With this standardization, many manufacturers added the device to their offerings ensuring low cost through robust competition.

:pushpin: Canonical Article: Meet the 2N2222 and 2N2907 General-Purpose Transistors

Figure 1 presents a good way to visualize the 2N2222 in relationship to other transistors. The arguably subjective radar chart shows the 2N2222 strengths along with the 2N3904 and the TIP41 power transistor chosen for contrast.

The desirable balance of the 2N2222 transistor is represented by the blue line where we see the 2N2222 scores favorably across many dimensions. The 2N3904 is similar, but slightly less capable across all dimensions except availability and cost where it appears to hold a slight advantage. The TIP41 shows considerable variation. The current is considerably higher at the expense of speed, cost, and current gain.

Figure 1: Subjective measure of transistor attributes on a scale of 1 to 10.
Figure 1: Subjective measure of transistor attributes on a scale of 1 to 10.752×452 25.3 KB

Figure 1: Subjective measure of transistor attributes on a scale of 1 to 10.

Popularity with Amateur Radio Enthusiasts

Amateur radio enthusiasts (Hams) have taken a keen interest in the 2N2222. This is reflected in over 60 years of literature including the latest American Radio Relay League (ARRL) handbook and a half century of QST and QEX magazines.

From time to time, we see competitions to see what can be done with 2N2222 transistors. Some projects are works of art using the 2N2222 for oscillators, low-signal amplification, signal steering, and even as power amplifier, and transceiver. See examples:

Popularity in Education

A quick web search will reveal thousands of articles featuring the 2N2222 transistor. The transistor may also be found in many textbooks and countless introductory articles. It’s safe to say that this device has momentum-of-the-decades ensuring past, present, and future applicability.

:writing_hand: Article by Aaron Dahlen, LCDR USCG (Ret.), Application Engineer at DigiKey. Author bio.