# TIP120

**STMicroelectronics** · Bipolar Transistor (BJT) · TO-220

The TIP120 is an NPN Darlington power transistor rated for 60 V and 5 A continuous collector current. Its Darlington pair gives a high current gain (2500 typical), so a small base current from an MCU or logic pin can switch large loads like motors, relays, solenoids, and lamps. It comes in a TO-220 package with integrated base-emitter resistors and a clamp diode is often paired externally for inductive loads.

## Pinout

| Pin | Name | Type | Function |
|---|---|---|---|
| 1 | B | input | Base of the NPN Darlington pair. Drives the input transistor through an internal 7 kΩ base-emitter shunt (R1); a second 70 Ω resistor (R2) shunts the output stage. Max continuous base current IB = 0.12 A; VBE(on) ≤ 2.5 V at IC = 3 A, VCE = 3 V. |
| 2 | C | passive | Collector of the NPN Darlington output transistor. Electrically common with the TAB (mounting/heat-sink flange). Rated VCEO = 60 V, IC(cont) = 5 A, IC(peak) = 8 A; VCE(sat) ≤ 2 V at IC = 3 A. Includes an internal collector-emitter clamp diode (anode = emitter, cathode = collector) for inductive-load flyback protection. |
| 3 | E | passive | Emitter of the NPN Darlington output transistor; the low-side current-return terminal. Typically tied to ground/common in a low-side switching topology. Carries the full collector current in the on state. |

## Key specifications

| Parameter | Value |
|---|---|
| Type | NPN Darlington power transistor |
| Collector-emitter voltage (VCEO) | 60 V |
| Collector current (IC) | 5 A continuous (8 A peak) |
| DC current gain (hFE) | 1000 min, 2500 typ at 3 A |
| Power dissipation | 65 W |
| VCE(sat) | 2.0 V at 3 A |
| Operating temperature | -65 C to 150 C |

## CAD (KiCad official)

- Symbol: `tip120.kicad_sym`
- Footprint: `tip120.kicad_mod`
- 3D model: TO-220 body from KiCad `Package_TO_SOT_THT/TO-220-3_Vertical`.
- 3D model files: `tip120-etched.step` / `tip120-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `tip120.step` / `tip120.glb` are the bare package body.

## Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

- **Datasheet:** [STMicroelectronics datasheet](https://www.st.com/resource/en/datasheet/tip120.pdf) (13 pp, sha256 `e726b0e3ab76c110`, retrieved 2026-08-17, tier: manufacturer)
- **Extractor:** `ds2sf` (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.
- **CAD:** KiCad official libraries (CC-BY-SA 4.0).

[Datasheet PDF](docs/tip120-datasheet.pdf)