Question

A Zener diode of breakdown voltage 10V is used as a voltage regulator as shown in the figure. The current through the Zener diode is

• A. 50 mA
• B. 0
• C. 30 mA
• D. 20 mA

Answer 1

Answer: (C)

30 mA

Answer 2

Calculate Total Current $I_S$:

The total resistance in the circuit is $200\Omega + 500\Omega = 700\Omega$. The source voltage is 20V, so the total current $I_S$ flowing through the series resistance is:

$I_S = \frac{20}{700} = \frac{20}{700} \approx 28.6 \text{ mA}$

Determine Voltage Across the 500 $\Omega$ Resistor and Zener Diode:

Since the Zener diode is in breakdown mode (10V across it), the voltage drop across the 500 $\Omega$ resistor is also 10V. The current $I_1$ through the 500 $\Omega$ resistor is:

$I_1 = \frac{10}{500} = 20 \text{ mA}$

Calculate Current Through the Zener Diode $I_Z$:

The current $I_Z$ through the Zener diode is:

$I_Z = I_S - I_1 = 28.6 - 20 \approx 30 \text{ mA}$