# BC557

**Changjiang Electronics Tech (CJ)** · Bipolar Transistors - BJT · TO-92

BC557 from Changjiang Electronics Tech (CJ), in a TO-92. 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 | COLLECTOR | passive | Collector of the PNP transistor; BC557 VCEO is -45 V, VCBO is -50 V and continuous collector current is -0.1 A. |
| 2 | BASE | passive | Base of the PNP transistor; BC557 emitter-base voltage limit VEBO is -5 V. |
| 3 | EMITTER | passive | Emitter of the PNP transistor; total device power dissipation is 625 mW at Ta=25°C. |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | Changjiang Electronics Tech (CJ) |
| Package | TO-92 |
| Category | Transistors |
| 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 breakdown voltage | V(BR)CBO | -50 |  |  | V | IC=-0.1mA, IE=0 | 2 |
| Collector-emitter breakdown voltage | V(BR)CEO | -45 |  |  | V | IC=-2mA, IB=0 | 2 |
| Emitter-base breakdown voltage | V(BR)EBO | -5 |  |  | V | IE=-100μA, IC=0 | 2 |
| Collector cut-off current | ICBO |  |  | -0.1 | μA | VCB=-45V, IE=0 | 2 |
| Emitter cut-off current | IEBO |  |  | -0.1 | μA | VEB=-5V, IC=0 | 2 |
| DC current gain | hFE | 120 |  | 800 |  | VCE=-5V, IC=-2mA | 2 |
| Collector-emitter saturation voltage | VCE(sat) |  |  | -0.3 | V | IC=-10mA, IB=-0.5mA | 2 |
| Collector-emitter saturation voltage | VCE(sat) |  |  | -0.65 | V | IC=-100mA, IB=-5mA | 2 |
| Base-emitter saturation voltage | VBE(sat) |  |  | -0.8 | V | IC=-10mA, IB=-0.5mA | 2 |
| Base-emitter saturation voltage | VBE(sat) |  |  | -1 | V | IC=-100mA, IB=-5mA | 2 |
| Base-emitter voltage | VBE | -0.55 |  | -0.7 | V | VCE=-5V, IC=-2mA | 2 |
| Transition frequency | fT | 150 |  |  | MHz | VCE=-5V, IC=-10mA, f=100MHz | 2 |
| Collector-base voltage | VCBO |  |  | -50 | V | Ta=25℃ | 1 |
| Collector-emitter voltage | VCEO |  |  | -45 | V | Ta=25℃ | 1 |
| Emitter-base voltage | VEBO |  |  | -5 | V | Ta=25℃ | 1 |
| Collector current-continuous | IC |  |  | -0.1 | A | Ta=25℃ | 1 |
| Collector power dissipation | PC |  |  | 625 | mW | Ta=25℃ | 1 |
| Junction temperature | Tj |  |  | 150 | ℃ |  | 1 |
| Storage temperature | Tstg | -55 |  | 150 | ℃ |  | 1 |
| Thermal resistance from junction to ambient | RθJA |  | 200 |  | ℃/W |  | 1 |
| Base-emitter voltage | VBE |  | -0.82 |  | V | VCE=-5V, IC=-10mA | 2 |
| Collector output capacitance | Cob |  | 6 |  | pF | VCB=-10V, IE=0, f=1MHz | 2 |

## CAD (KiCad official)

- Symbol: `BC557`
- Footprint: `Package_TO_SOT_THT:TO-92_Inline`
- 3D model: TO-92 (KiCad packages3D, STEP)
- 3D model files: `bc557-etched.step` / `bc557-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `bc557.step` / `bc557.glb` are the bare package body.

## Provenance

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

- **Datasheet:** [Changjiang Electronics Tech (CJ) datasheet](docs/bc557-datasheet.pdf) (4 pp, sha256 `81775b75ec2ea3df`, retrieved 2026-10-22, tier: lcsc)
- **Extractor:** parts-factory `2.0.0` / `extract_pins 0.3`, primary `claude-sonnet-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/bc557-datasheet.pdf)