In a Zener voltage regulator circuit, the unregulated input voltage is 50 V and the Zener breakdown voltage is 10 V . The series resistance is 1000 . For the Zener diode to maintain regulation, it requires a minimum current of 15 mA . The minimum value of the load resistance that can be connected across the Zener diode is ________ .

Step-by-step solution

The voltage drop across the series resistor R is constant as long as the Zener diode is in breakdown: V_R = V_i - V_Z = 50 - 10 = 40 V The total current flowing through the series resistor is: I_S = V_R R = 40 1000 = 0.04 A = 40 mA The total current I_S splits into the Zener current I_Z and the load current I_L . To find the minimum load resistance, the load current must be at its maximum allowable value. This occurs when the Zener current is at its minimum required value to maintain regulation: I_ L( max ) = I_S -