Zener Diode Power and Series Resistor Calculator

A Zener diode is an electronic component used in DC voltage regulator circuits. This calculator will calculate the maximum current and the necessary series resistance to protect the Zener diode.

Inputs

V_source

Volt

V_out

Volt

I_max

Output

Zener diode power rating

Resistance value

Resistance power rating

The power rating of a Zener diode indicates the maximum power that the diode can safely dissipate. Knowing the maximum current that can flow through the Zener diode is important, because exceeding its power rating can damage or destroy the component. In the equation below, power equals the voltage multiplied by the current.

Equation

$$I_{ZM} =\frac{P_{ZM}}{V_Z}$$

where:

I_ZM is the maximum current that can flow through the diode

P_ZM is the diode’s maximum power dissipation,

V_Z is the Zener voltage.

Example: If a Zener diode has a voltage of 5.1 V and a power rating of 1 W, what is the maximum current that can flow through the diode?

$$I_{ZM} =\frac{P_{ZM}}{V_Z} =\frac{1.0}{5.1} = 0.196 \text{ A} = 196 \text{ mA}$$

Application

Zener diodes can be used in simple voltage regulator circuits, such as the one shown below. Note that the 1 kΩ series resistor limits the current through the 12.6 V Zener diode.