Description
The 48V 0.5W Zener diode is a specialized component often used for high-voltage regulation, voltage clamping, or protecting sensitive electronics from overvoltage surges. The industry-standard part number for this specification is the 1N5261.
Technical Specifications
| Parameter | Specification |
| Nominal Zener Voltage ($V_Z$) | 48V |
| Power Dissipation ($P_D$) | 0.5W (500mW) |
| Package Type | DO-35 or DO-41 (Axial Lead) |
| Tolerance | $\pm 5\%$ |
| Operating Temperature | -65°C to +200°C |
Understanding the Zener Principle
This component is designed to operate in the reverse breakdown region. When the input voltage exceeds 48V, the diode begins to conduct, effectively “clamping” the output voltage to a stable 48V by shunting excess current to ground.
To function as a regulator, you must install the diode in reverse bias (cathode to the positive potential) and include a series current-limiting resistor ($R_s$). This is critical: without this resistor, the diode would draw unregulated current, exceed its 500mW power limit, and likely fail as a short circuit.
Application & Safety Guidelines
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Thermal Management: To keep this 500mW device safe, ensure the current ($I_Z$) flowing through it does not exceed the limit. Using the formula $I_{Zmax} = P_D / V_Z$, your maximum current should be kept below ~10.4mA ($0.5W / 48V$).
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Procurement: You requested 2 pieces. These are specialized parts; you can find them by searching for “1N5261” or “48V 500mW Zener”.
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Troubleshooting: If the voltage on your 48V rail is zero or lower than expected, check the Zener diode. A failed Zener diode typically measures as a dead short (near 0 ohms) in both directions on a multimeter.
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