Zener diodes permit current both forward and backwards, if the voltage is greater than the breakdown voltage or ‘Zener voltage'. A reverse-based Zener diode will exhibit a controlled breakdown and allow current to keep voltage across the Zener diode close to the Zener voltage. Vishay, Fagor and Semikron are the leading Zener diode brands from Rapid. All are available in axial lead packages for easy circuit installation.