This is a circuit to test zener diodes. It hooks up to a 120V AC line and boosts the output voltage to over 300V allowing you to test zener diodes of any voltage. The circuit also has a push button switch to triple the current, if needed. The output is attached to 2 pairs of alligator clips. One pair is to attach to the diode. The second pair is to attach to a multimeter. The voltage across the diode is show on you multimeter.


It should be noted that this circuit could be dangerous. It is tied directly to an AC line, and has an output of 300V. The output has resistors on each line, which limits the current making it a bit safer, but will still give you quite a shock.

It should be switched off while attaching diode


  • S1: SPDT switch
  • S2: Pushbutton switch
  • N1: Neon lamp
  • D1: 1N4004, 1A 400V Rectifier
  • D2: 1N4004, 1A 400V Rectifier
  • C1: Electrolytic Capacitor 100uF 200V
  • C2: Electrolytic Capacitor 100uF 200V
  • R1: 33kΩ Resistor 1/2W
  • R2: 2.7kΩ Resistor 1/4W
  • R3: 1MΩ Resistor 1/4W
  • R4: 24kΩ Resistor 1W, or 2x 48kΩ Resistor 1/2W in parallel.
  • R5: 48kΩ Resistor 1W, or 2x 100kΩ Resistor 1/2W in parallel.
  • 4x alligator clips




to be added

Community content is available under CC-BY-SA unless otherwise noted.