Zener Diode Voltage Regulators A zener diode is to be used as a voltage regulator. The zener diode was tested at the operating point Vzt = 6.2 V, Izt=15 mA. At this bias point(a). What series resistance R is required to put the zener diode at the dc bias Vzt, Izt? (b). If the voltage source has a fluctuation of AV = +1 V, what is the output voltage fluctuation Avl across the load?