The **SC945** (often labeled as C945) is a widely used NPN epitaxial silicon transistor. It is designed for use in audio frequency amplification and high-speed switching applications. It is frequently paired with the **SA733** (PNP complement). --- ### 1. Key Technical Specifications The following table summarizes the absolute maximum ratings and electrical characteristics of the SC945: | Parameter | Symbol | Rating | Unit | | :--- | :--- | :--- | :--- | | 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 | | Collector Power Dissipation | $P_C$ | 400 | mW | | DC Current Gain | $h_{FE}$ | 70 to 700 | - | | Transition Frequency | $f_T$ | 150 | MHz | --- ### 2. Pinout Configuration The SC945 typically comes in a **TO-92** plastic package. It is important to check the datasheet of the specific manufacturer, as some versions (especially those from different regions) may swap pins. | Pin Number | Name | Function | | :--- | :--- | :--- | | 1 | **Emitter** | Current exits the transistor | | 2 | **Collector** | Current enters the transistor | | 3 | **Base** | Controls the biasing/switching | --- ### 3. Applications and Features The SC945 is favored in electronics for several reasons: * **Low Noise:** It has a low noise figure, making it excellent for the initial stages of audio pre-amplifiers. * **High Linearity:** It provides stable gain across a range of frequencies. * **Switching:** Due to its high transition frequency ($150\text{ MHz}$), it can handle fast switching in digital circuits. * **Common Uses:** * Signal amplifiers. * Sensor circuits. * LED driving (up to $150\text{ mA}$). * Oscillator circuits. --- ### 4. Equivalent Replacements If the SC945 is unavailable, the following transistors are common functional equivalents: * **2N2222:** (Higher current handling, but different pinout). * **BC547:** (Standard European NPN, check pinout). * **2SC1815:** (Very similar performance and often interchangeable). ---