The **2SD874A-R** is a NPN epitaxial silicon transistor designed primarily for low-frequency power amplification and driver stage circuits. It is characterized by its high current capacity and low saturation voltage. --- ## 1. Key Technical Specifications The following table summarizes the absolute maximum ratings and electrical characteristics for the 2SD874A-R. | Parameter | Symbol | Rating/Value | 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)** | $I_C$ | 1 | A | | **Collector Power Dissipation** | $P_C$ | 1 | W | | **Junction Temperature** | $T_j$ | 150 | °C | | **DC Current Gain** | $h_{FE}$ | 120 to 240 | - | --- ## 2. Pin Configuration The device is typically housed in a **TO-92L** (also known as TO-92MOD) package, which is slightly larger than a standard TO-92 to allow for better heat dissipation. | Pin Number | Name | Description | |:---:|:---:|:---| | 1 | **Emitter** | Current exits the transistor | | 2 | **Collector** | Current enters the transistor | | 3 | **Base** | Controls the gate/biasing | --- ## 3. The "R" Classification The suffix **"R"** in 2SD874A-R refers to the **hFE (Current Gain) Rank**. Manufacturers categorize these transistors into ranges to provide consistency in circuit design: * **Q Rank:** 85 to 170 * **R Rank:** 120 to 240 * **S Rank:** 170 to 340 --- ## 4. Typical Applications Because of its 1A current handling and high gain, it is commonly used in: 1. **Audio Amplifiers:** Used in the driver stage to push power to the final output transistors. 2. **Voltage Regulators:** Part of a linear power supply circuit. 3. **Relay Drivers:** Switching medium-sized inductive loads. 4. **DC-DC Converters:** Small-scale power conversion. --- ## 5. Complementary Pair The PNP complement to the 2SD874A is the **2SB766A**. Using these two together allows for the design of Push-Pull amplifier stages.