JEE MainPhysicsSemiconductors
A voltage regulator circuit is powered by a fixed DC source of 25 V . The regulating branch consists of a Zener diode (breakdown voltage 8 V ) and a standard PN junction diode (forward voltage drop 1 V ) connected in series, with the PN diode being forward-biased. This entire regulating branch is connected in parallel with a load resistor of 500 . A series resistor of 500 connects the unregulated source to the parall
Correct answer
14
Step-by-step solution
The regulating branch consists of a Zener diode and a forward-biased PN junction diode in series. The total regulated voltage across this branch (and therefore across the load) is the sum of their voltage drops: V_ reg = V_z + V_d = 8 V + 1 V = 9 V The current flowing from the source through the series resistor R_s is: I_s = V_ in - V_ reg R_s = 25 V - 9 V 500 = 16 500 A = 32 mA The current flowing through the load resistor R_L is: I_L = V_ reg R_L = 9 V 500 = 18 mA Applying Kirchhoff's Current Law at the junction,