# BF840

**Nexperia** · Bipolar (BJT) · SOT-23

BF840 from Nexperia, in a SOT-23. Pinout and pin descriptions extracted from the manufacturer datasheet (extract_pins, cross-checked by a second model); symbol, footprint, and 3D from KiCad-official CAD.

## Pinout

| Pin | Name | Type | Function |
|---|---|---|---|
| 1 | B | passive | Base terminal of the NPN transistor; the datasheet gives the emitter-base limit VEBO of 4 V max (open collector) and a 25 mA maximum collector current. |
| 2 | E | passive | Emitter terminal of the NPN transistor; emitter-base voltage is limited to VEBO = 4 V (open collector), with the 25 mA maximum collector current and 40 V maximum collector-base and collector-emitter voltages referenced to it. |
| 3 | C | passive | Collector terminal of the NPN transistor; limited to VCBO = 40 V (open emitter) and VCEO = 40 V (open base), with a DC and peak collector current of 25 mA maximum. |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | Nexperia |
| Package | SOT-23 |
| Category | Transistors/Thyristors |
| Pins | 3 |

## Electrical characteristics

Limits as printed in the datasheet (page.json `metadata.characteristics` carries them as data).

| Parameter | Symbol | Min | Typ | Max | Unit | Conditions | Page |
|---|---|---|---|---|---|---|---|
| Collector cut-off current | ICBO |  |  | 100 | nA | IE = 0; VCB = 20 V | 4 |
| Emitter cut-off current | IEBO |  |  | 100 | nA | IC = 0; VEB = 4 V | 4 |
| DC current gain | hFE | 67 |  | 222 |  | IC = 1 mA; VCE = 10 V | 4 |
| Base-emitter voltage | VBE | 675 | 725 | 775 | mV | IC = 1 mA; VCE = 10 V | 4 |
| Collector-base voltage | VCBO |  |  | 40 | V | open emitter | 3 |
| Collector-emitter voltage | VCEO |  |  | 40 | V | open base | 3 |
| Emitter-base voltage | VEBO |  |  | 4 | V | open collector | 3 |
| Collector current (DC) | IC |  |  | 25 | mA |  | 3 |
| Peak collector current | ICM |  |  | 25 | mA |  | 3 |
| Total power dissipation | Ptot |  |  | 250 | mW | Tamb ≤ 25 °C; note 1 | 3 |
| Storage temperature | Tstg | -65 |  | 150 | °C |  | 3 |
| Junction temperature | Tj |  |  | 150 | °C |  | 3 |
| Operating ambient temperature | Tamb | -65 |  | 150 | °C |  | 3 |
| Thermal resistance from junction to ambient | Rth(j-a) |  | 500 |  | K/W | note 1 (transistor mounted on FR4 PCB) | 4 |

## CAD (KiCad official)

- Symbol: `BF840`
- Footprint: `Package_TO_SOT_SMD:SOT-23`
- 3D model: SOT-23 (KiCad packages3D, STEP)
- 3D model files: `bf840-etched.step` / `bf840-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `bf840.step` / `bf840.glb` are the bare package body.

## Provenance

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

- **Datasheet:** [Nexperia datasheet](https://assets.nexperia.com/documents/data-sheet/BF840.pdf) (7 pp, sha256 `7c62d5cca3f51f7b`, retrieved 2026-10-17, tier: manufacturer)
- **Extractor:** parts-factory `2.0.0` / `extract_pins 0.3`, primary `claude-haiku-5-5` (text), consensus `claude-sonnet-5-5` (agreed), guards: pin_guards 0.1: passed. Pins are checked against the footprint pad set and their cited datasheet pages before publish.
- **CAD:** KiCad official libraries (CC-BY-SA 4.0).

[Datasheet PDF](docs/bf840-datasheet.pdf)