The TIP120 is an NPN Darlington power transistor designed for general-purpose amplifier and low-speed switching applications. Unlike standard transistors, the Darlington configuration consists of two transistors in a single package connected so that the current amplified by the first is amplified further by the second. This results in an extremely high current gain, allowing low-power signals from microcontrollers like Arduino or ESP32 to control high-power loads such as large motors, solenoids, and high-intensity LED strips. It is a staple in the maker community for projects requiring robust power handling.
TIP120 Pinout (TO-220)
The TIP120 comes in the TO-220 package. When looking at the front (the side with the part number) with the pins pointing down, the pins are arranged from left to right as Base, Collector, and Emitter.
| Pin | Terminal | Function |
| 1 | Base (B) | Control terminal to trigger the Darlington pair |
| 2 | Collector (C) | Connected to the load; also connected to the metal tab |
| 3 | Emitter (E) | Current returns to the ground through this pin |
Technical Specifications
- Transistor Polarity: NPN Darlington
- Collector-Emitter Voltage (VCEO): 60V
- Collector-Base Voltage (VCBO): 60V
- Emitter-Base Voltage (VEBO): 5V
- Collector Current (IC): 5A (Continuous)
- Peak Collector Current (ICM): 8A
- DC Current Gain (hFE): 1000 (Minimum at 3A)
- Max Power Dissipation (PD): 65W (with heat sink)
Key Features & Benefits
- High Current Gain: High sensitivity allows switching 5A loads with only a few milliamps of input.
- Integrated Protection Diode: Includes a built-in damper diode between the collector and emitter to protect against inductive spikes.
- Heatsink Friendly: The TO-220 package can be easily bolted to a heatsink for high-power applications.
- Low Threshold: Easily triggered by 5V logic signals.
Common Applications
- Motor Control: Driving DC motors and high-torque actuators.
- Solenoid Drivers: Perfect for controlling heavy-duty pneumatic or hydraulic valves.
- Power Inverters: Used in simple DC-to-AC conversion circuits.
- Lighting: Switching high-power LED arrays or incandescent lamps.
TIP120 Equivalent & Substitutes
- TIP121 / TIP122 (Higher voltage versions of the same series)
- 2N6043 (Similar power rating)
- BDW93C (High power Darlington alternative)
- IRLZ44N (Logic-level MOSFET alternative for high-speed switching)
Related Tutorials on ElxHub
- Basics: Learn more in Transistors – Basics, Types, and Working
- Signal Shifting: Learn how to bridge logic levels in our Logic Level Shifter Tutorial
- Selection Guide: Compare power options in our Ultimate Transistor Selection Guide
Conclusion
The TIP120 is the go-to component for any designer needing to bridge the gap between low-power logic and heavy-duty hardware. Its Darlington architecture provides the necessary muscle for demanding tasks while remaining simple to use in a standard circuit. When your project outgrows the capacity of small signal transistors, the TIP120 is the most reliable next step.
Download the Transistor Datasheet pdf
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