Consider the circuit shown in the figure below The zener diode ha
The zener diode has a zener breakdown voltage of Vz = 10V and has the maximum amount of zener current Iz(max) = 20 mA. The zener diode turns on when the voltage of 10V is applied over it with nearly zero Knee current, then the value of load resistance RL for proper regulation should be in the range
A. RL > 100Ω
B. 10Ω < RL < 100Ω
C. 250Ω < RL < 500Ω
D. 2500Ω < RL < 500Ω
Please scroll down to see the correct answer and solution guide.
Right Answer is: C
SOLUTION
The minimum value of load resistance can be calculated when maximum current flows through the load.
Thus, IL(max) = Iin – Iz(min)
Iz(min) = 0 
knee current nearly equal to zero
IL(max) = Iin
Now, for maximum value of load resistance, we will calculate minimum value of current through load.
IL(min) = Iin – Iz(max)
IL(min) = (40 – 20) × 10–3
= 500 Ω
