The **SC945** (often labeled as C945) is a widely used NPN epitaxial silicon transistor. It is specifically designed for use in high-frequency applications, audio frequency amplifiers, and general-purpose switching. --- ### 1. Technical Specifications Below are the primary electrical characteristics of the SC945 transistor: | Parameter | Symbol | Rating | Unit | | :--- | :--- | :--- | :--- | | **Type** | - | NPN | - | | **Collector-Base Voltage** | $V_{CBO}$ | 60 | V | | **Collector-Emitter Voltage** | $V_{CEO}$ | 50 | V | | **Emitter-Base Voltage** | $V_{EBO}$ | 5 | V | | **Collector Current (DC)** | $I_C$ | 150 | mA | | **Power Dissipation** | $P_C$ | 400 | mW | | **DC Current Gain** | $h_{FE}$ | 90 to 600 | - | | **Transition Frequency** | $f_T$ | 150 | MHz | --- ### 2. Pinout Configuration The SC945 is most commonly found in the **TO-92** plastic package. Looking at the flat side with the leads pointing downwards, the pinout is typically: 1. **Emitter (E):** Current exits the transistor here. 2. **Collector (C):** Current enters the transistor here. 3. **Base (B):** The trigger that controls the flow between Collector and Emitter. > **Note:** Always check the specific manufacturer datasheet, as some versions (like the 2SC945) may swap the Collector and Base pins. --- ### 3. Key Applications * **Audio Amplification:** Low noise figure makes it suitable for pre-amplifier stages. * **Switching:** Used in low-power switching circuits (driving LEDs, small relays). * **RF Oscillators:** High transition frequency allows it to operate in AM/FM radio circuits. * **Voltage Regulation:** Often found in simple voltage stabilizer circuits. --- ### 4. Comparison with Complementary Part In push-pull amplifier configurations, the SC945 (NPN) is frequently paired with its PNP counterpart: * **Complementary Pair:** **SA733** (or A733) ### 5. Common Alternatives If the SC945 is unavailable, the following transistors are often used as functional substitutes: * **2N3904** (Standard NPN, though pinout may differ) * **BC547** (Common European NPN) * **SS9014** (Low noise NPN)