From a 3.3 V or 5 V pin
| Pin | Verdict | Why | In free air |
|---|---|---|---|
| ESP32 · 3.3 V | Works | 150 Ω on the base: up to 140 mA of load at a gain of 10 | 140 mA (pin current) |
| Arduino Uno · 5 V | Works | 220 Ω on the base: up to 171 mA of load at a gain of 10 | 171 mA (pin current) |
In free air at 25 °C, with the junction 25 °C below its 150 °C maximum and θJA 200 °C/W, from a 20 mA pin at the datasheet’s forced gain, and no further than the highest current with a guaranteed saturation voltage.
Specifications
| Type | NPN |
|---|---|
| Package | TO-92 |
| Maximum voltage | 40 V |
| Maximum current | 600 mA |
| Minimum gain hFE | 100 at 150 mA · 40 at 500 mA |
| VCE(sat), maximum | 0.3 V at 150 mA (IC = 10 × IB) · 1 V at 500 mA (IC = 10 × IB) |
| VBE(sat), maximum | 1.2 V at 150 mA (IC = 10 × IB) · 2 V at 500 mA (IC = 10 × IB) |
| Thermal resistance | θJA 200 °C/W |
| Maximum junction temperature | 150 °C |
| Datasheet used | onsemi (P2N2222A) |
Pinout
| Pin | Function |
|---|---|
| 1 | Collector |
| 2 | Base |
| 3 | Emitter |
Flat face toward you, leads down: pin 1 is on the left. This is the onsemi P2N2222A. Other 2N2222A and PN2222A in TO-92, and the metal-can 2N2222A, may use a different order: check the datasheet of the part you have.
Similar parts
| Part | Package | VCE(sat), guaranteed | Max voltage | Max current |
|---|---|---|---|---|
| 2N2222A | TO-92 | 1 V at 500 mA (IC = 10 × IB) | 40 V | 600 mA |
| 2N3904 | TO-92 | 0.3 V at 50 mA (IC = 10 × IB) | 40 V | 200 mA |
| BC547 | TO-92 | 0.6 V at 100 mA (IC = 20 × IB) | 45 V | 100 mA |
| S8050 | SOT-23 | 0.6 V at 500 mA (IC = 10 × IB) | 25 V | 500 mA |
| TIP120 | TO-220 | 4 V at 5 A (IC = 250 × IB) | 60 V | 5 A |
Tips
The base resistor is sized for IC = 10 × IB, the condition of the datasheet’s saturation voltage. A higher gain from the hFE column would leave the transistor half on and hot.
Every coil needs a flyback diode across it, cathode to the positive supply. Without it the voltage spike at turn-off can destroy the transistor at the first switching.
Open the calculator →Check the 2N2222A with your own load, supply, PWM frequency and temperature.
Other transistors
2N3904 BC547 S8050 TIP120 2N7000 BS170 AO3400A Si2302 IRLML6344 IRLZ44N IRLB8721 IRF520 IRF540N AO3401A IRF9540N
Frequently asked questions
Does the 2N2222A work with a 3.3 V ESP32?
Yes, with a base resistor: at the gain of 10 the datasheet uses for saturation, a 20 mA pin drives the 2N2222A up to 140 mA of load. For more current use a logic-level MOSFET.
How much current can the 2N2222A switch without a heatsink?
About 171 mA from a 5 V Arduino pin, in free air at 25 °C, keeping the junction 25 °C below its 150 °C maximum (limit: pin current).
What is the 2N2222A pinout?
TO-92: 1 collector, 2 base, 3 emitter. Flat face toward you, leads down: pin 1 is on the left. This is the onsemi P2N2222A. Other 2N2222A and PN2222A in TO-92, and the metal-can 2N2222A, may use a different order: check the datasheet of the part you have.
Source of the figures: onsemi (P2N2222A) datasheet (PDF)