Description
The 30V 0.5W Zener diode is a standard component used for voltage regulation and transient overvoltage protection. It is most commonly identified by the industry-standard part number 1N5256 or the BZX79-C30 series.
Technical Specifications
| Parameter | Specification |
| Nominal Zener Voltage ($V_Z$) | 30V |
| Power Dissipation ($P_D$) | 0.5W (500mW) |
| Package Type | DO-35 (Small Glass Axial) |
| Tolerance | $\pm 5\%$ |
| Operating Temperature | -65°C to +200°C |
Operating Principle
This component is engineered to operate in the reverse breakdown region. When the input voltage exceeds 30V, the diode begins to conduct, effectively “clamping” the potential to a stable 30V by shunting excess current to ground.
To operate as a regulator, you must use a series current-limiting resistor ($R_s$). This resistor limits the current ($I_Z$) flowing through the diode, preventing it from exceeding its 0.5W power rating. Without this resistor, the diode will quickly overheat and fail, typically in a short-circuit state.
Application & Safety Guidelines
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Thermal Management: To keep this 500mW device safe, ensure the current ($I_Z$) does not exceed the limit. Using the formula $I_{Zmax} = P_D / V_Z$, your maximum current should be kept below ~16.6mA ($0.5W / 30V$).
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Procurement: You requested 2 pieces. These are widely available; search for “1N5256” or “BZX79-C30” to find this exact specification.
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Troubleshooting: If the circuit output is 0V or significantly lower than 30V, test the Zener diode with a multimeter. A failed Zener diode will typically show a dead short (near 0 ohms) in both directions.
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