2N2222 Transistor NPN General-Purpose
The 2N2222 transistor operates as a versatile NPN bipolar junction transistor designed for low-to-moderate power amplification and switching. Engineers choose this transistor for its reliable operation in analog and digital circuits. It handles currents up to 800 mA, supports collector-emitter voltages up to 40 V, and switches rapidly, making it ideal for control systems, signal processing, and low-power applications.
When you forward bias the base-emitter junction, the transistor conducts from collector to emitter. When you remove base current, it turns off and blocks collector current. This behavior makes it well-suited for interfacing with logic circuits, relays, motors, LEDs, and other loads.
Most manufacturers offer the 2N2222A variant in a TO-18 metal can package, which provides better thermal performance than the common plastic-cased PN2222.
Pin Configuration (TO-18 Package)
| Pin | Name | Description |
|---|---|---|
| 1 | Emitter | Current flows out |
| 2 | Base | Controls conduction state |
| 3 | Collector | Current flows in |
Note: In TO-92 (plastic) versions like PN2222, the pin order may differ.
Key Features
Provides fast switching performance
Supports up to 800 mA collector current
Handles 40 V collector-emitter voltage
Offers current gain (hFE) of 100–300
Comes in metal (TO-18) or plastic (TO-92) packages
Works well in analog and digital logic systems
Applications
Switch low-power relays, solenoids, or motors.
Drive LEDs or small lamps from logic outputs.
Amplify analog signals in audio or sensor circuits.
Interface between microcontrollers and higher current loads.
Generate pulse-width modulated control signals.
Build basic oscillator or timer circuits.
Buffer digital outputs to reduce load.
Replace general-purpose NPN transistors like BC547 in prototyping.
Construct discrete logic gates or bistable circuits.
Use in educational labs for transistor behavior analysis.
Specifications Table
| Parameter | Value |
|---|---|
| Transistor Type | NPN |
| Max Collector Current | 800 mA |
| Max Collector-Emitter Voltage | 40 V |
| Max Collector-Base Voltage | 75 V |
| Max Emitter-Base Voltage | 6 V |
| DC Current Gain (hFE) | 100–300 |
| Max Power Dissipation | 500 mW (TO-18) |
| Transition Frequency (fT) | 250 MHz |
| Saturation Voltage (VCEsat) | ~0.3 V ‘ |
| Package Type | TO-18, TO-92 |
| Operating Temperature | -55 to +150 °C |
