Zener Diode Calculator

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Calculate the series resistance Rs to stabilize a voltage with a Zener diode, the current in the diode and the power dissipated in the components.

Rs = (Vin − Vz) / (Iz + Il) Power Rs and Zener Suggested E12 value

Parameters

Vin — Input voltage (V)

Vz — Zener voltage (V)

The — Load current (mA)

Iz — Min Zener current (mA)

How do I calculate Zener series resistor?

Rs = (Vin − Vz) / (Iz + Il). Typical Iz = 10mA plus load current.

What power rating for the Zener diode?

Pz = Vz × Iz. With Vz=5.1V, Iz=20mA: Pz = 102mW. Use 0.5W Zener for margin.