A zener diode with 5 V zener voltage is used to regulate an unregulated dc voltage input of 25 V.
For a 400 Ω resistor connected in series, the zener current is found to be 4 times load current. The load current (IL) and load resistance (RL) are: [2025]
(4)
5IL=(25-5)400=120=50 mA
IL=10 mA
5=ILRL
RL=5IL=510×10-3=500 Ω