Introduction
The TIP121 NPN transistor is a widely used Darlington power transistor designed for high current and medium voltage applications. Built using two NPN transistors in a Darlington pair configuration, it delivers exceptionally high DC current gain, making it ideal for switching and amplification purposes where only a small base current is available. Its ability to handle significant loads makes it popular in robotics, motor driving, relay controls, and audio circuits.
With a collector current capacity of 5A and a maximum collector-emitter voltage of 80V, the TIP121 can drive motors, solenoids, and high-power LEDs directly. Its high current gain (hFE up to 1000) allows it to be triggered by low-power logic signals from microcontrollers such as Arduino, Raspberry Pi, and PIC controllers, making it a preferred choice in automation and embedded systems.
TIP121 NPN Transistor
Encapsulated in a TO-220 package, the TIP121 offers efficient heat dissipation, and with proper heatsinking, it can dissipate up to 65W of power. This ensures reliable operation in demanding environments. Its durability, affordability, and compatibility with other TIP12x family transistors make it a trusted choice for both hobbyists and professional circuit designers.
TIP121 Pinout
TIP121 Transistor Key Features
- Darlington pair design for very high current gain.
- Suitable for medium to high power switching applications.
- Compatible with microcontroller and logic-level signals.
- Low base current required for switching heavy loads.
- TO-220 package supports efficient cooling with a heatsink.
- Reliable choice for robotics, automation, and audio circuits.
Specifications/Characteristics of TIP121 NPN Transistor
- Transistor Type: NPN Darlington
- Collector-Emitter Voltage (Vce): 80V
- Collector-Base Voltage (Vcb): 80V
- Emitter-Base Voltage (Veb): 5V
- Collector Current (Ic): 5A (continuous)
- Peak Collector Current: 8A
- DC Current Gain (hFE): 1000 (typical)
- Power Dissipation (Ptot): 65W
- Package Type: TO-220
- Operating Temperature Range: -65°C to +150°C
TIP121 Pin Configuration
| Pin# | Pin Name | Pin Description |
|---|---|---|
| 1 | Base | Controls the transistor (input signal). |
| 2 | Collector | Current flows through the load. |
| 3 | Emitter | Connected to ground or return path. |
More Circuit Layouts
Key Applications of TIP121 NPN Transistor
- Relay and solenoid driver circuits.
- DC and stepper motor controllers.
- High-power LED drivers.
- Power amplifiers.
- Switching high current loads from microcontrollers.
- Industrial automation and robotics.
PNP Complimentary Transistor
TIP126 (PNP Darlington transistor) is the complementary pair of TIP121.
Equivalent Transistors of TIP121
- TIP120 (NPN Darlington, 60V version)
- TIP122 (NPN Darlington, 100V version)
- BDW93 (NPN Darlington alternative)
- 2N6284 (high current NPN Darlington)
- MJE800 series as functional equivalents
(Pin configuration of some transistors mentioned here may different from TIP121).
Datasheet of TIP121 NPN Transistor
Click the following Button below to download the datasheet of TIP121 Transistor :
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