## Overview of the 2SD874-R Transistor The **2SD874-R** is an NPN epitaxial planar silicon transistor designed primarily for low-frequency power amplification and driver stage applications. It is often found in audio equipment, voltage regulators, and switching circuits. --- ### 1. Key Technical Specifications The "R" suffix typically denotes the **hFE (DC Current Gain)** classification, indicating a specific gain range. | Parameter | Symbol | Maximum Rating | Unit | | :--- | :--- | :--- | :--- | | Collector-Base Voltage | $V_{CBO}$ | 30 | V | | Collector-Emitter Voltage | $V_{CEO}$ | 25 | V | | Emitter-Base Voltage | $V_{EBO}$ | 5 | V | | Collector Current (DC) | $I_C$ | 1 | A | | Collector Current (Pulse) | $I_{CP}$ | 1.5 | A | | Collector Power Dissipation | $P_C$ | 1 | W | | Junction Temperature | $T_j$ | 150 | °C | --- ### 2. Gain Classification (hFE) The 2SD874 is sorted into ranks based on its current gain. The **R** rank is defined as follows: | Rank | hFE Range | | :--- | :--- | | **R** | **180 to 390** | | S | 260 to 520 | --- ### 3. Physical Packaging and Pinout The device usually comes in a **TO-92L** (also known as TO-92MOD) package, which is slightly taller than a standard TO-92 to allow for better heat dissipation. **Pin Configuration (Front View):** 1. **Emitter (E)** 2. **Collector (C)** 3. **Base (B)** --- ### 4. Typical Applications * **Audio Amplifiers:** Used in the driver stage of small to medium power amplifiers. * **Voltage Regulation:** Acts as a pass transistor in linear power supply circuits. * **Relay Drivers:** Capable of switching 1A loads, making it suitable for driving solenoids and relays. * **DC-DC Converters:** Employed in low-power switching applications. --- ### 5. Complementary Pair The PNP counterpart for the 2SD874 is the **2SB766**. Using these together allows for the design of "Push-Pull" amplifier stages.