A voltage regulator circuit uses a Zener diode with a breakdown voltage of 6 V connected in parallel with a variable load resistor R_L . A series resistor R connects this parallel combination to a fixed DC input voltage of 15 V . The value of R is chosen such that the Zener diode just maintains regulation (i.e., Zener current approaches zero) when the load resistance is at its minimum allowed value of 200 . If the lo

Step-by-step solution

When the load resistance is at its minimum value R_ L, = 200 , the load current is maximum. I_ L, = V_Z R_ L, = 6 200 = 0.03 A = 30 mA The problem states that at this minimum load resistance, the Zener diode just maintains regulation, meaning the Zener current I_Z 0 . The total current through the series resistor R is I_R = I_Z + I_ L, = 0 + 30 mA = 30 mA . The value of the series resistor R can be found using the voltage drop across it: R = V_i - V_Z I_R = 15 - 6 30 10⁻³ = 9 0.03 = 300 When the load resistor is co