# A42

**Changjing** · Bipolar (BJT) · SOT-89-3L

A42 from Changjing, in a SOT-89-3L. 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 A42 NPN transistor; base-emitter saturation voltage is 0.9 V at IC=20 mA, IB=2 mA. |
| 2 | COLLECTOR | passive | Collector terminal; ratings are VCBO 310 V, VCEO 305 V, continuous IC 200 mA, pulsed ICM 500 mA, and PC 500 mW. |
| 3 | EMITTER | passive | Emitter terminal; the emitter-base breakdown voltage V(BR)EBO is 5 V minimum at IE=100 µA, and VEBO is rated 5 V. |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | Changjing |
| Package | SOT-89-3L |
| Category | Transistors/Thyristors |
| Pins | 3 |

## CAD (KiCad official)

- Symbol: `A42`
- Footprint: `Package_TO_SOT_SMD:SOT-89-3`
- 3D model: SOT-89-3L (KiCad packages3D, STEP)
- 3D model files: `a42-etched.step` / `a42-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `a42.step` / `a42.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/8586174277293260800) (4 pp, sha256 `11f21ca090c652e3`, 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/a42-datasheet.pdf)