It appears you are referring to the **40635**, which is a historical and specialized high-power NPN Silicon Transistor, originally manufactured by RCA (and later cross-referenced by brands like Central Semiconductor). This part was primarily designed for high-voltage power switching and amplifier applications. --- ### 1. Technical Specifications Below are the typical electrical characteristics for the 40635 transistor: | Parameter | Description | Typical Value | | :--- | :--- | :--- | | **Type** | Polarized Semiconductor | NPN | | **Material** | Semiconductor Base | Silicon | | **Package Style** | Case Type | TO-3 (Metal Can) | | **V_ceo** | Collector-Emitter Voltage | 400V - 450V | | **I_c** | Continuous Collector Current | 5A - 10A | | **P_d** | Total Power Dissipation | ~100W - 125W | | **h_fe** | DC Current Gain | 15 - 60 (approx) | --- ### 2. Key Features and Construction * **TO-3 Package:** The device is housed in a "Diamond" metal TO-3 package. This design is chosen for its superior heat dissipation capabilities, as the metal case acts as the collector and is usually bolted directly to a large heat sink. * **High Voltage Rating:** With a breakdown voltage often exceeding 400V, it was a staple in early solid-state power supplies. * **Ruggedness:** These transistors were built for industrial durability, capable of handling significant thermal stress. --- ### 3. Common Applications The 40635 was widely used in electronics before the mass adoption of MOSFETs and IGBTs. Common use cases included: 1. **Deflection Circuits:** Used in old CRT (Cathode Ray Tube) monitors and television sets. 2. **Inverters:** Converting DC battery power to AC power. 3. **Switching Regulators:** Early high-efficiency power supply designs. 4. **Audio Amplifiers:** High-power output stages for professional audio equipment. --- ### 4. Modern Equivalents and Replacements Because the 40635 is an older, often obsolete part, technicians frequently look for modern substitutes. Common replacements (depending on the specific circuit requirements) include: * **MJ15024:** A robust NPN power transistor in a TO-3 package. * **2N3055:** (Only for lower voltage applications; **caution required** as the 2N3055 has a much lower voltage rating). * **BUX48A:** High voltage, high current NPN transistor. > **Note:** Always verify the Pinout (Base, Emitter, Collector) and the Safe Operating Area (SOA) when substituting power transistors.