# FCX491TA

**Diodes Incorporated** · Bipolar (BJT) · SOT-89

FCX491TA from Diodes Incorporated, in a SOT-89. Pinout and pin descriptions extracted from the manufacturer datasheet by ds2sf; symbol, footprint, and 3D from KiCad-official CAD.

## Pinout

| Pin | Name | Type | Function |
|---|---|---|---|
| 1 | B | input | Base terminal of the NPN transistor. Drive current into the base to turn the device on; VBE(on) ≈ 0.83 V typ, VBE(sat) ≈ 0.965 V typ at IC = 1 A, IB = 100 mA. Emitter-base breakdown VEBO = 7 V min. |
| 2 | C | passive | Collector terminal of the NPN transistor; also bonded to the SOT89 exposed back-side heat-slug tab. Rated VCEO = 60 V, VCBO = 80 V, IC = 1 A continuous / ICM = 2 A peak. Tab acts as the primary thermal path (RθJL = 22 °C/W). |
| 3 | E | passive | Emitter terminal of the NPN transistor. Reference terminal for VBE and VCE; VCE(sat) ≈ 160 mV typ at IC = 1 A, IB = 100 mA. |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | Diodes Incorporated |
| Package | SOT-89 |
| Category | Transistors/Thyristors |
| Pins | 3 |

## Ordering variants

Same part, different packaging or reel option.

- `FCX491TA`
- `FCX491TAQTA`

## CAD (KiCad official)

- Symbol: `FCX491TA`
- Footprint: `Package_TO_SOT_SMD:SOT-89-3`
- 3D model: SOT-89 (KiCad packages3D, STEP)
- 3D model files: `fcx491ta-etched.step` / `fcx491ta-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `fcx491ta.step` / `fcx491ta.glb` are the bare package body.

## Provenance

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

- **Datasheet:** [Diodes Incorporated datasheet](https://jlcpcb.com/api/file/downloadByFileSystemAccessId/8586193920275992576) (7 pp, sha256 `52c218b9396374d4`, retrieved 2026-08-17, tier: lcsc)
- **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/fcx491ta-datasheet.pdf)