# MMBT3904M 1N

**Changjing** · Bipolar (BJT) · SOT-723

MMBT3904M 1N from Changjing, in a SOT-723. 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 | BASE | input | Base terminal of the NPN transistor; the datasheet rates the emitter-base voltage VEBO at 6 V and gives a base-emitter saturation voltage of 0.65 to 0.85 V at IC=10 mA, IB=1 mA. |
| 2 | EMITTER | passive | Emitter terminal of the NPN transistor; the datasheet rates the emitter-base breakdown voltage V(BR)EBO at 6 V minimum at IE=10 µA. |
| 3 | COLLECTOR | passive | Collector terminal of the NPN transistor; the datasheet rates the collector-emitter voltage VCEO at 40 V and the continuous collector current IC at 0.2 A. |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | Changjing |
| Package | SOT-723 |
| Category | Transistors/Thyristors |
| Pins | 3 |

## CAD (KiCad official)

- Symbol: `MMBT3904M 1N`
- Footprint: `Package_TO_SOT_SMD:SOT-723`
- 3D model: SOT-723, generated from the KiCad footprint (body from the F.Fab outline, terminals on the pads, 0.5 mm nominal SOT-723 height). Neither the vendor nor KiCad ships a 3D model for this package, so the dimensions are nominal, not the manufacturer's CAD (STEP)
- 3D model files: `mmbt3904m-1n-etched.step` / `mmbt3904m-1n-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `mmbt3904m-1n.step` / `mmbt3904m-1n.glb` are the bare package body.

## Provenance

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

- **Datasheet:** [Changjing datasheet](https://jlcpcb.com/api/file/downloadByFileSystemAccessId/8586202716355350528) (4 pp, sha256 `d122b2d7b26b65bc`, retrieved 2026-10-09, tier: lcsc)
- **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/mmbt3904m-1n-datasheet.pdf)