What Is the TIP120? NPN Darlington: Pinout and High-Current Drive
The TIP120 is a high-current NPN Darlington power transistor. By cascading two transistors internally it gives very high current gain (hFE>1000), driving loads such as motors/relays (5 A continuous, 8 A peak) from an MCU's small current. Its TO-220 pinout is B-C-E and it has an internal freewheel diode. Its high saturation voltage makes it heat up, so a heatsink is needed.
The TIP120 is a high-current NPN Darlington power transistor. By cascading two transistors internally it provides very high current gain (hFE > 1000), so a microcontroller's small output current can drive large loads. For the concept, see what is a transistor.
What is the TIP120 used for?
Switching high-current loads such as motors, relays, solenoids, high-power LED strips and heaters with a small control current. It can be driven directly from an Arduino/MCU pin (with a small base resistor). It contains an internal freewheel diode and base-emitter resistors.
TIP120 pinout (TO-220)
With the front (labelled) face toward you, leads down, left to right: B – C – E.
| Pin | Function |
|---|---|
| 1 | Base (B) |
| 2 | Collector (C) |
| 3 | Emitter (E) |
The metal tab is connected to the collector.
Key electrical specifications
| Parameter | Typical value |
|---|---|
| Type | NPN Darlington |
| VCEO | 60 V |
| IC (continuous) | 5 A (peak 8 A) |
| hFE | > 1000 (Darlington) |
| Internal diode | Yes (freewheel) |
Watch out: high saturation voltage and heat
Because of the Darlington structure, the collector-emitter saturation voltage (VCE(sat)) is high (~1–2 V); at high current it produces significant heat → a heatsink is needed. If efficiency is critical, use a logic-level MOSFET (e.g. the IRFZ44N/IRLZ44N) instead.
TIP120 equivalents and alternatives
- TIP121 / TIP122: the same family at higher voltage.
- TIP125 / TIP126 / TIP127: the PNP Darlington counterparts.
- IRFZ44N / IRLZ44N: a more efficient MOSFET alternative.
- ULN2003: a 7-channel Darlington array (for many channels).
Find it in our catalog
To compare price and stock for the TIP120 and its alternatives, use the TIP120 search.