## BD237 NPN Power Transistor The **BD237** is a silicon epitaxial base **NPN power transistor** housed in a TO-126 plastic package. It is designed for use in medium-power linear and switching applications. ### 1. Key Technical Specifications The following table outlines the absolute maximum ratings and electrical characteristics for the BD237: | Parameter | Symbol | Maximum Value | Unit | | :--- | :--- | :--- | :--- | | Collector-Emitter Voltage | $V_{CEO}$ | 80 | V | | Collector-Base Voltage | $V_{CBO}$ | 100 | V | | Emitter-Base Voltage | $V_{EBO}$ | 5 | V | | Collector Current (DC) | $I_C$ | 2 | A | | Collector Current (Peak) | $I_{CM}$ | 6 | A | | Total Power Dissipation ($T_c = 25^\circ C$) | $P_{tot}$ | 25 | W | | DC Current Gain ($I_C = 0.5A, V_{CE} = 2V$) | $h_{FE}$ | 40 - 160 | - | --- ### 2. Pin Configuration (TO-126 Package) When looking at the front of the transistor (the side with the part number marking), the pins are ordered as follows: 1. **Pin 1 (Left):** Emitter 2. **Pin 2 (Center):** Collector (also connected to the metal mounting tab) 3. **Pin 3 (Right):** Base --- ### 3. Common Applications Due to its moderate power handling and voltage rating, the BD237 is frequently used in: * **Audio Amplifiers:** Used in the output or driver stages of medium-power audio systems. * **Switching Regulators:** Acting as a switch to control loads up to 2A. * **Relay Drivers:** Driving solenoids, relays, or small DC motors from microcontroller signals. * **Signal Buffer:** Used in circuits requiring a current boost without significant voltage loss. --- ### 4. Complementary Pair In "Push-Pull" amplifier configurations, the BD237 (NPN) is often paired with its PNP counterpart: * **Complementary PNP:** **BD238** ---