The **2SD1815-R** (often abbreviated as **D1815-R**) is a popular NPN Silicon Epitaxial Planar Transistor. It is primarily designed for high-frequency amplification and general-purpose switching applications. --- ### 1. Key Specifications The "R" suffix in the part number typically refers to the **hFE (DC Current Gain)** classification, indicating a specific range of gain for that batch. | Parameter | Symbol | Maximum Rating | | :--- | :--- | :--- | | **Collector-Base Voltage** | $V_{CBO}$ | 60V | | **Collector-Emitter Voltage** | $V_{CEO}$ | 50V | | **Emitter-Base Voltage** | $V_{EBO}$ | 5V | | **Collector Current (DC)** | $I_C$ | 150mA | | **Collector Power Dissipation** | $P_C$ | 400mW | | **Junction Temperature** | $T_j$ | 150°C | --- ### 2. Physical Characteristics & Pinout The D1815 is commonly found in the **TO-92** plastic package. When looking at the flat side of the transistor with the leads pointing down, the pin configuration is as follows: 1. **Emitter (E)**: The output lead for the current. 2. **Collector (C)**: The lead connected to the positive supply (in NPN). 3. **Base (B)**: The trigger lead that controls the flow between E and C. --- ### 3. Gain Classification (hFE) Manufacturers categorize the 2SD1815 into different "hFE" ranks. The **"R"** classification usually falls into the following range: * **R Rank:** 180 to 390 * *O (Orange): 70–140* * *Y (Yellow): 120–240* * *G (Green): 200–400* * *L (Blue): 350–700* --- ### 4. Typical Applications The D1815-R is versatile and used in low-power electronic circuits: * **Audio Preamplifiers**: Used for low-noise signal boosting. * **Switching**: Driving small LEDs, relays, or acting as a logic gate component. * **High-Frequency Stages**: Often found in AM/FM radio receiver circuits due to its transition frequency ($f_T$) of approximately 80MHz. * **Signal Processing**: Used in television and consumer electronics for signal buffering. --- ### 5. Complementary Pair In push-pull amplifier designs, the D1815 (NPN) is often paired with its PNP counterpart: * **PNP Complement**: **2SA1015**