MMBT3904E

ST Semtech · Bipolar (BJT) · SOT-523

MMBT3904E from ST Semtech, in a SOT-523. 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	input	Base; emitter-base voltage limited to 6 V (VEBO) and base saturation voltage 0.65 to 0.85 V at IC = 10 mA, IB = 1 mA.
2	E	passive	Emitter; common terminal of the NPN transistor, with VEBO max 6 V and VCEO max 40 V relative to the collector.
3	C	passive	Collector; VCBO 60 V, VCEO 40 V and continuous collector current IC up to 200 mA.

Key specifications

Parameter	Value
Manufacturer	ST Semtech
Package	SOT-523
Category	Transistors/Thyristors
Pins	3

CAD (KiCad official)

Symbol: MMBT3904E
Footprint: Package_TO_SOT_SMD:SOT-523
3D model: SOT-523, generated from the KiCad footprint (body from the F.Fab outline, terminals on the pads, 0.8 mm nominal SOT-523 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: mmbt3904e-etched.step / mmbt3904e-etched.glb carry the MPN laser-etched on the die in a toggleable Adom.LaserEtch group (Fusion-ready); mmbt3904e.step / mmbt3904e.glb are the bare package body.

Provenance

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

Datasheet: ST Semtech datasheet (5 pp, sha256 e6aec3f169c23a6f, retrieved 2026-10-09, tier: lcsc)
Extractor: parts-factory 2.0.0 / extract_pins 0.3, primary claude-sonnet-5-5 (text+vision), consensus claude-opus-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

# MMBT3904E

**ST Semtech** · Bipolar (BJT) · SOT-523

MMBT3904E from ST Semtech, in a SOT-523. 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 | input | Base; emitter-base voltage limited to 6 V (VEBO) and base saturation voltage 0.65 to 0.85 V at IC = 10 mA, IB = 1 mA. |
| 2 | E | passive | Emitter; common terminal of the NPN transistor, with VEBO max 6 V and VCEO max 40 V relative to the collector. |
| 3 | C | passive | Collector; VCBO 60 V, VCEO 40 V and continuous collector current IC up to 200 mA. |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | ST Semtech |
| Package | SOT-523 |
| Category | Transistors/Thyristors |
| Pins | 3 |

## CAD (KiCad official)

- Symbol: `MMBT3904E`
- Footprint: `Package_TO_SOT_SMD:SOT-523`
- 3D model: SOT-523, generated from the KiCad footprint (body from the F.Fab outline, terminals on the pads, 0.8 mm nominal SOT-523 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: `mmbt3904e-etched.step` / `mmbt3904e-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `mmbt3904e.step` / `mmbt3904e.glb` are the bare package body.

## Provenance

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

- **Datasheet:** [ST Semtech datasheet](https://jlcpcb.com/api/file/downloadByFileSystemAccessId/8590908391474737152) (5 pp, sha256 `e6aec3f169c23a6f`, retrieved 2026-10-09, tier: lcsc)
- **Extractor:** parts-factory `2.0.0` / `extract_pins 0.3`, primary `claude-sonnet-5-5` (text+vision), consensus `claude-opus-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/mmbt3904e-datasheet.pdf)