BC108 NPN Metal Transistor 20V 100mA TO-18
The BC108 is a silicon planar epitaxial NPN bipolar transistor housed in a TO-18 metal can. It is optimized for low-noise, small-signal applications (audio preamps, input stages, oscillators) and offers stable DC gain and good frequency response in compact through-hole form. The metal package gives better thermal conduction and mechanical robustness compared with plastic packages, which helps reliability in hand-built and professional analog circuits.
Because the BC108 is specified for low currents and modest voltages it is ideal for pre-amplifier stages, driver stages and general purpose signal processing where low noise and predictable gain are important. Its straightforward pinout and long history in vintage and educational designs make it a common choice for repairs, hobby projects and low-power analog designs.
Features:
- Low noise performance suitable for audio and input stages.
- Stable DC current gain with grouped hFE options.
- Metal TO-18 package for improved heat dissipation.
- Good small-signal frequency response.
- Robust mechanical package for through-hole assembly.
- Widely available and easy to source for repairs and prototypes.
Specifications:
| Parameter | Value |
|---|---|
| Device type: | NPN bipolar transistor |
| Package: | TO-18 (metal can) |
| Collector-Base breakdown (VCBO): | 30V |
| Collector-Emitter breakdown (VCEO): | 20V |
| Emitter-Base breakdown (VEBO): | 5V |
| Max collector current (IC): | 100mA |
| Power dissipation (Ptot): | 0.3W (Ta ≤ 25°C) / 0.75 W (Tc ≤ 25°C) |
| DC current gain (hFE): | Groups: A/B/C (ranges 110–450 depending on group and test) |
| Transition frequency (fT): | ~150MHz (small-signal) |
| Input capacitance (CCBO): | ~4–6pF |
| Storage temperature: | −55°C to +175°C |
| Max junction temperature (Tj): | 175°C |
Pinout:
| Pin Number | Pin Name |
|---|---|
| 1 | Emitter |
| 2 | Base |
| 3 | Collector |
| Case | Collector |
Applications:
- Audio input and pre-amplifier stages.
- Small-signal amplification (sensors, instrumentation).
- Oscillators and signal-processing circuits.
- Low-power switching and driver stages (relays, small loads).
- Repair and restoration of vintage electronics.
- Educational electronics and prototyping.
