2N2222 Transistor Pinout, Features, and Applications

There is no safe universal 2N2222 pin order. Read the exact part marking and identify the package before wiring it. Metal TO-18 2N2222A is E-B-C viewed from the bottom, with the emitter nearest the locating tab. PN2222A in plastic TO-92 is E-B-C with the flat face toward you and the leads pointing down. P2N2222A in plastic TO-92 is C-B-E in that same flat-face view, the exact reverse of the PN2222A.

Assuming one lead order fits every device is the most common cause of a dead 2N2222. A reversed emitter and collector may prevent the circuit from working and can damage the transistor.

What Is a 2N2222 Transistor?

The 2N2222 family contains NPN bipolar junction transistors used for switching and small-signal amplification. The base controls collector-emitter current, while the emitter and collector carry the controlled current path.

The letters around 2222 matter. The metal 2N2222A, plastic PN2222A, and plastic P2N2222A are related parts, but their names do not guarantee the same package, lead order, or absolute maximum ratings.

What each transistor pin does

Terminal function does not reveal physical lead position. Use the package-qualified table above for wiring.

2N2222 vs 2N2222A: What Is the Difference?

The A suffix identifies an improved electrical revision. It does not mean plastic packaging. Central Semiconductor specifies both the 2N2222 and 2N2222A in metal TO-18 cases.

Sources: the Central Semiconductor 2N2222 datasheet and the Central Semiconductor 2N2222A datasheet.

PN2222A and P2N2222A are plastic-package manufacturer part names. Do not use the A suffix alone to choose a footprint.

2N2222 Absolute Maximum Ratings

Absolute maximums are stress limits, not recommended operating points. The values differ by exact manufacturer part, so the marking must stay attached to every number.

Plastic-device sources: the Fairchild PN2222A datasheet and the onsemi P2N2222A datasheet.

The Fairchild PN2222A absolute maximum table lists 1.0 A, while the same datasheet introduces the device for switching currents up to 500 mA. Design current must also satisfy power dissipation, temperature, gain, and safe-drive requirements.

2N2222 Alternatives and Equivalents

Possible alternatives include PN2222A, P2N2222A, 2N3904, BC337, and BC547, but none should be treated as a pin-for-pin replacement by name alone.

Before substituting, compare polarity, package lead order, VCEO, VCBO, VEBO, continuous collector current, power dissipation, gain at the intended current, and switching speed. The 2N2907 and 2N3906 are PNP devices, so they are not direct NPN equivalents for the 2N2222.

Can You Use a BC547 Instead of a 2N2222?

A BC547 can replace a 2N2222 only when the circuit stays within the BC547 datasheet limits and the footprint is rewired for the exact device. It is not a drop-in substitute.

Check collector current, voltage, power, gain, and package lead order. Do not rotate a transistor on the board based on a generic TO-92 drawing because BC547 pinouts also depend on the manufacturer and package.

How to Identify the 2N2222 Package and View

Use this sequence before connecting any 2N2222-family transistor:

1. Read the complete body marking, including the PN or P2N prefix and A suffix.
2. Identify the metal TO-18 or plastic TO-92 package.
3. Use the viewpoint printed in that manufacturer's datasheet.
4. Match each numbered lead to E, B, or C before soldering or choosing a PCB footprint.

For a metal TO-18 2N2222A, use a bottom view and locate the tab. Lead 1 is the emitter nearest the tab, lead 2 is the base, and lead 3 is the collector. The collector is internally connected to the case, as documented in the Microchip 2N2222A package drawing.

For the PN2222A and P2N2222A in the plastic TO-92 package, held with the flat face toward you and the leads pointing downward, PN2222A is E-B-C from left to right, while P2N2222A is C-B-E.

Basic 2N2222 Example Circuits

The 2N2222 is commonly used as a low-side NPN switch. The load connects between the positive supply and collector, the emitter returns to ground, and a resistor limits base current from the control signal.

LED low-side switch example

For a 5 V supply, a red LED with a 2.0 V forward drop, and a 10 mA target, an assumed 0.2 V saturated transistor gives R = (5 - 2.0 - 0.2) / 0.01 = 280 Ω. A standard 330 Ω LED resistor provides margin.

For a conservative forced gain of 10, 10 mA collector current needs about 1 mA of base current. With a 5 V control signal and an assumed 0.8 V base-emitter drop, Rbase = (5 - 0.8) / 0.001 = 4.2 kΩ. Round DOWN to the nearest standard value, 3.9 kΩ, which supplies about 1.08 mA and keeps the forced gain near 9. Rounding up to 4.7 kΩ would give only 0.89 mA, a forced gain above 11, and less saturation margin than intended. Recalculate for the actual LED, supply, control voltage, and transistor.

DC motor low-side switch example

Connect the motor between its positive supply and the collector, connect the emitter to ground, and drive the base through a resistor. Join the controller and motor-supply grounds.

Place a flyback diode across the motor with its cathode at the positive supply and its anode at the collector. Confirm that motor stall current, not only running current, stays within the exact transistor's current and power limits.

2N2222 Operating and Safety Checks

• Treat absolute maximum ratings as damage thresholds, not design targets.
• Calculate transistor dissipation from collector-emitter voltage and collector current.
• Use a base resistor and verify that the controller can supply the required base current.
• Clamp inductive loads with a correctly oriented flyback diode.
• Check the exact package pinout again before applying power.

2N2222 Applications

• Low-side switching for LEDs, relays, solenoids, and small motors within ratings
• Small-signal common-emitter amplification
• Pulse switching and logic-level interfacing
• Oscillators and signal-conditioning stages

For an analog example using a transistor pair, see the BJT differential amplifier guide.

2N2222 Pinout FAQs

What is the function of a 2N2222 transistor?

The 2N2222 is an NPN bipolar transistor. A small base current controls a larger collector-emitter current, allowing the device to act as a switch or amplifier.

How do you use a 2N2222 pinout?

First identify the exact marking and package. Then use the matching viewpoint and lead order from the table at the top of this page, calculate the base and load resistors, and keep voltage, current, power, and temperature below the exact datasheet limits.

Summary

The correct 2N2222 pinout depends on the exact marking and package. Metal TO-18 2N2222A is E-B-C from the bottom view, PN2222A is E-B-C with the TO-92 flat face toward you, and P2N2222A in TO-92 is C-B-E in that same flat-face view.

Never copy a bare three-letter lead order onto a footprint. Verify the marking, viewpoint, and manufacturer datasheet, then apply the ratings for that exact part.

Need help preparing a board around this transistor? Contact OurPCB to discuss fabrication and assembly requirements.