NPN transistor · TO-92
2N2222A Pinout
Flat face toward you, legs pointing down, left to right: 1 emitter, 2 base, 3 collector (E-B-C).
The classic general-purpose NPN for currents up to about 500 mA: relays, small motors, LED groups.
- Pin 1: Emitter (E)Goes to 0 V (ground) when the transistor is used as a switch.
- Pin 2: Base (B)The control pin. A small current into it, always through a resistor, switches the transistor on.
- Pin 3: Collector (C)Goes to the load (LED, relay, buzzer). Current flows in here and out of the emitter.
Check your part before wiring. Read the maker and the full part number printed on it, open that maker's datasheet, or test the legs with a multimeter's diode setting.
PNG 1440 × 1280 pixels, SVG to any size. Both keep the wirecora.com mark along the bottom.
Pinout table
Which leg of the 2N2222A is which?
| Pin | Name | What it does |
|---|---|---|
| 1 | Emitter E | Goes to 0 V (ground) when the transistor is used as a switch. |
| 2 | Base B | The control pin. A small current into it, always through a resistor, switches the transistor on. |
| 3 | Collector C | Goes to the load (LED, relay, buzzer). Current flows in here and out of the emitter. |
Key ratings
How much can the 2N2222A take?
From the onsemi (Fairchild) datasheet: PN2222A NPN General-Purpose Amplifier, TO-92 (Rev. 1.1.0). Stay well inside these limits: they are the most the part takes, not what it should run at.
Open the onsemi (Fairchild) datasheet (PDF)Pin order by maker
Is every 2N2222A wired E-B-C?
The 2N2222A was first made in a small metal can (TO-18), where a little tab on the rim sits next to the emitter. In that can the collector is joined to the metal case (Microchip's 2N2222A datasheet, DS00005314A, note 9), so the can must not touch other parts or wires.
In plastic TO-92 the part is the PN2222A, or simply marked 2N2222A. The PN2222A datasheet (the one quoted here) gives E-B-C with the flat face toward you.
onsemi's P2N2222A, also TO-92 and also sold as a 2N2222A, is the opposite: its datasheet numbers the legs 1 collector, 2 base, 3 emitter (C-B-E). Two parts both called 2N2222A can go in the opposite way round, so read the full number on yours.
Also quoted above:
A first circuit
Drive a 5 V relay from an Arduino pin
- Relay coil from +5 V to the collector. Emitter to 0 V.
- A diode (1N4007) across the coil, its striped end to +5 V. It takes the voltage kick when the coil switches off.
- A 1 kΩ resistor from a 5 V Arduino pin to the base (470 Ω from a 3.3 V pin). That gives about 4 mA of base current, plenty for a coil of 70 to 90 mA.
- Pin high: the relay clicks on. Pin low: it lets go.
Leave the diode out and the coil's kick can kill the transistor the first time the relay turns off.
The wiring board has the PN2222A, the plastic 2N2222A with E-B-C legs, in its Transistors group.
Open the wiring board2N2222A questions
What is the 2N2222A pinout?
For the common plastic PN2222A, flat face toward you and legs down: emitter, base, collector (E-B-C). onsemi's P2N2222A is C-B-E, and the metal-can 2N2222A has its own layout, so check the exact part number.
How much current can a 2N2222A switch?
The PN2222A datasheet gives 1.0 A as the absolute limit and names the part for currents up to 500 mA. Keep heat in mind: 625 mW in free air is not much.
Is the 2N2222A the same as the PN2222A?
Electrically very close: the PN2222A is the plastic TO-92 version of the metal-can 2N2222A. Kit parts are usually marked plain "2N2222A" and most are E-B-C, but onsemi's P2N2222A is C-B-E. Read the full marking, and check the legs with a multimeter's diode test or hFE socket before wiring.
Can I use a 2N2222A instead of a BC547?
Yes, and it handles more current. Mind the legs: the PN2222A is E-B-C, the BC547 is C-B-E.
Can I use this pinout picture?
Yes. Download it as PNG or SVG and use it in notes, lessons or posts. The wirecora.com mark along the bottom stays in the picture.
Pin order and ratings from the onsemi (Fairchild) datasheet named above. Last reviewed .