# BCX42

**YFW** · Bipolar (BJT) · SOT-23

BCX42 from YFW, 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 | input | Base of the PNP transistor; Ib max -100 mA (peak -200 mA), emitter-base voltage max -5 V. |
| 2 | E | passive | Emitter of the PNP transistor; emitter-base breakdown BVEBO is -5 V. |
| 3 | C | passive | Collector of the PNP transistor; Ic max -800 mA (peak -1 A), BVCEO -125 V, Ptot 330 mW. |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | YFW |
| 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-base voltage | BVCBO |  |  | -125 | V |  | 1 |
| Collector-emitter voltage | BVCEO |  |  | -125 | V |  | 1 |
| Emitter-base voltage | BVEBO |  |  | -5 | V |  | 1 |
| Collector current | IC |  |  | -800 | mA |  | 1 |
| Peak collector current | ICM |  |  | -1 | A |  | 1 |
| Base current | IB |  |  | -100 | mA |  | 1 |
| Peak base current | IBM |  |  | -200 | mA |  | 1 |
| Total power dissipation | Ptot |  |  | 330 | mW |  | 1 |
| Junction temperature | Tj |  |  | 150 | ℃ |  | 1 |
| Storage temperature | Tstg | -55 |  | 150 | ℃ |  | 1 |
| Junction - soldering point thermal resistance | RθJS |  |  | 215 | ℃/W |  | 1 |
| Collector-base breakdown voltage | BVCBO | -125 |  |  | V | IC = -100μA, IE = 0 | 2 |
| Collector-emitter breakdown voltage | BVCEO | -125 |  |  | V | IC = -1mA, IB = 0 | 2 |
| Emitter-base breakdown voltage | BVEBO | -5 |  |  | V | IE = -100μA, IC = 0 | 2 |
| Collector cut-off current | ICBO |  |  | -0.1 | μA | VCB = -100V, IE = 0 | 2 |
| Collector-emitter cutoff current | ICEO |  |  | -10 | μA | VCE = -100V, IB = 0 | 2 |
| Emitter cut-off current | IEBO |  |  | -0.1 | μA | VEB = -4V, IC = 0 | 2 |
| DC current gain | hFE | 25 |  |  |  | VCE = -1V, IC = -0.1mA | 2 |
| DC current gain | hFE | 63 |  |  |  | VCE = -1V, IC = -100mA | 2 |
| DC current gain | hFE | 40 |  |  |  | VCE = -1V, IC = -200mA | 2 |
| Collector-emitter saturation voltage | VCE(sat) |  |  | -0.9 | V | IC = -300mA, IB = -30mA | 2 |
| Base-emitter saturation voltage | VBE(sat) |  |  | -1.4 | V | IC = -300mA, IB = -30mA | 2 |
| Gian bandwidth product | fT | 150 |  |  | MHZ | VCE = -5V, IC = -20mA, f=20MHz | 2 |
| Collector-base capacitance | Cob |  |  | 12 | pF | VCB = -10V, IE = 0, f=1MHz | 2 |

## CAD (KiCad official)

- Symbol: `BCX42`
- Footprint: `Package_TO_SOT_SMD:SOT-23`
- 3D model: SOT-23 (KiCad packages3D, STEP)
- 3D model files: `bcx42-etched.step` / `bcx42-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `bcx42.step` / `bcx42.glb` are the bare package body.

## Provenance

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

- **Datasheet:** [YFW datasheet](https://jlcpcb.com/api/file/downloadByFileSystemAccessId/8603346072966213632) (4 pp, sha256 `de7ba898e04f78fa`, retrieved 2026-10-17, 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/bcx42-datasheet.pdf)