By John Papiewski – Updated March 24 2022
Diodes conduct current in a single direction. When reverse‑biased beyond their breakdown voltage, a standard diode will conduct and fail. A Zener diode is engineered to maintain a fixed reverse voltage, making it an inexpensive and reliable voltage regulator. In this guide we’ll walk through selecting the correct resistor, wiring the Zener, and ensuring safe operation.
Determine the resistor value with the formula:
R = (V_in – V_z) / I_z
For a 10 V supply with a target Zener voltage of 10 V and a desired current of 10 mA, R = 10 V / 0.01 A = 1 kΩ. The resistor wattage should be at least twice the calculated dissipation:
P = I_z² × R × 2 → (0.01)² × 1000 × 2 = 0.2 W
Use a ¼‑watt (0.25 W) resistor or larger.
Order the resistor and a Zener diode (e.g., 10 V, 1 W) from a reputable electronics distributor.
Cut four 8‑inch lengths of 22‑AWG solid wire and strip about ½ inch from each end.
Insert the Zener’s cathode (marked end) into one breadboard column and the anode into another. Connect two wires to the anode leads, and one resistor lead plus a third wire to the cathode. Place the resistor’s free lead in an unused column and tie the remaining wire to that same column.
Attach the free end of the last wire to the positive terminal of your DC source. Connect the free end of one anode wire to the negative terminal.
The wire connected to the Zener’s cathode now provides a stable positive output, while the anode wire gives the negative reference. This pair can power downstream circuits.
Zener diodes cover voltage ratings from 2.4 V to ~200 V, enabling versatile voltage regulation.
Never exceed the Zener’s maximum current rating; doing so will destroy the component.
