### 2SC2139 Transistor Overview The **2SC2139** is a Silicon NPN epitaxial planar type transistor. It is primarily designed for high-frequency amplification and oscillator applications, specifically in the VHF (Very High Frequency) range. It is often found in radio communication equipment and television tuners. --- ### Key Technical Specifications The following table summarizes the absolute maximum ratings and electrical characteristics typically associated with the 2SC2139: | Parameter | Symbol | Rating | Unit | | :--- | :--- | :--- | :--- | | **Collector-Base Voltage** | $V_{CBO}$ | 30 | V | | **Collector-Emitter Voltage** | $V_{CEO}$ | 20 | V | | **Emitter-Base Voltage** | $V_{EBO}$ | 4 | V | | **Collector Current** | $I_C$ | 30 | mA | | **Collector Power Dissipation** | $P_C$ | 250 | mW | | **Junction Temperature** | $T_j$ | 150 | °C | | **Transition Frequency** | $f_T$ | 600 (Typ) | MHz | --- ### Physical and Structural Details 1. **Package Type:** It usually comes in a **TO-92** small plastic package, which is standard for low-power signal transistors. 2. **Pin Configuration:** * **Pin 1:** Emitter * **Pin 2:** Collector * **Pin 3:** Base *(Note: Always verify with the specific manufacturer datasheet as pinouts can occasionally vary by region or brand.)* 3. **Polarity:** **NPN**. This means the device is turned "ON" when a positive voltage/current is applied to the base relative to the emitter. --- ### Common Applications * **VHF Amplifiers:** Due to its high transition frequency ($f_T$) of approximately 600 MHz, it is excellent for amplifying signals in the FM radio and VHF TV bands. * **Local Oscillators:** Used in mixing circuits to generate carrier frequencies. * **RF Signal Processing:** Suitable for low-noise pre-amplifiers in communication receivers. --- ### Equivalent / Substitute Parts If the 2SC2139 is unavailable, the following transistors may serve as functional equivalents, though parameters like gain ($h_{FE}$) and pin layout should be double-checked: * **2SC1923** * **2SC9018** * **BF199** (General RF NPN) * **KSC2688**