# BC858A

**MSKSEMI** · Bipolar (BJT) · SOT-23

BC858A from MSKSEMI, 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 | BASE | passive | Base terminal of the BC858A PNP transistor, the control electrode for switching and AF amplifier use; the datasheet gives VBE(sat) of -1.1 V max at IC=-100 mA, IB=-5 mA. |
| 2 | EMITTER | passive | Emitter terminal of the BC858A PNP transistor; the datasheet gives an emitter-base voltage rating VEBO of -5 V. |
| 3 | COLLECTOR | passive | Collector terminal of the BC858A PNP transistor; the datasheet gives VCEO of -30 V for the BC858 type and continuous collector current IC of -0.1 A. |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | MSKSEMI |
| 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-emitter saturation voltage | VCE(sat) |  |  | -0.5 | V | IC=-100mA, IB=-5mA | 2 |
| Base-emitter saturation voltage | VBE(sat) |  |  | -1.1 | V | IC=-100mA, IB=-5mA | 2 |
| DC current gain (BC858A) | hFE | 125 |  | 250 |  | VCE=-5V, IC=-2mA | 2 |
| Collector cut-off current (BC858) | ICBO |  |  | -0.1 | μA | VCB=-25 V, IE=0 | 2 |
| Emitter cut-off current | IEBO |  |  | -0.1 | μA | VEB=-5 V, IC=0 | 2 |
| Collector-base breakdown voltage (BC858) | VCBO | -30 |  |  | V | IC=-10μA, IE=0 | 2 |
| Collector-emitter breakdown voltage (BC858) | VCEO | -30 |  |  | V | IC=-10mA, IB=0 | 2 |
| Emitter-base breakdown voltage | VEBO | -5 |  |  | V | IE=-1μA, IC=0 | 2 |
| Collector-base voltage (BC858) | VCBO |  |  | -30 | V |  | 2 |
| Collector-emitter voltage (BC858) | VCEO |  |  | -30 | V |  | 2 |
| Emitter-base voltage | VEBO |  |  | -5 | V |  | 2 |
| Collector current, continuous | IC |  |  | -0.1 | A |  | 2 |
| Collector power dissipation | PC |  |  | 200 | mW |  | 2 |
| Operation junction and storage temperature range | TJ,Tstg | -55 |  | 150 | ℃ |  | 2 |
| Thermal resistance, junction to ambient | RΘJA |  |  | 625 | ℃/W |  | 2 |

## CAD (KiCad official)

- Symbol: `BC858A`
- Footprint: `Package_TO_SOT_SMD:SOT-23`
- 3D model: SOT-23 (KiCad packages3D, STEP)
- 3D model files: `bc858a-etched.step` / `bc858a-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `bc858a.step` / `bc858a.glb` are the bare package body.

## Provenance

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

- **Datasheet:** [MSKSEMI datasheet](https://jlcpcb.com/api/file/downloadByFileSystemAccessId/8603119731067277312) (5 pp, sha256 `c3419a6a6d96abdd`, retrieved 2026-10-18, 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/bc858a-datasheet.pdf)