Question

A zener diode of power rating 1.6 W is used as a voltage regula tor. If the zener diode has a breakdown voltage of 8 V and it has to regulate voltage fluctuating between 3 V and 10 V, what is the value of resistance Rs for safe operation of the diode?

• A. 10 Ω
• B. 12 Ω
• C. 13 Ω
• D. 13.3 Ω

Hint:

For Zener diode regulator design, always calculate the resistor value based on the maximum input voltage to ensure the Zener diode doesn’t exceed its power rating. Neglecting load current provides a safety margin

Answer 1

The Correct Option is A

To find the resistance R_s for the safe operation of the Zener diode, we need to consider the maximum current that the Zener diode can handle. The power rating of the Zener diode is given as 1.6 W, and the breakdown voltage is 8 V.

First, calculate the maximum Zener current (I_{Z_{max}}) the diode can handle using the power formula:

P = V_Z \times I_{Z_{max}}

where:

• P = 1.6 \, \text{W} (power rating)
• V_Z = 8 \, \text{V} (Zener breakdown voltage)

Solve for I_{Z_{max}}:

I_{Z_{max}} = \frac{P}{V_Z} = \frac{1.6}{8} = 0.2 \, \text{A}

Next, consider the maximum input voltage V_s = 10 \, \text{V}. The Zener diode should maintain the voltage at 8V, so the voltage across R_s is:

V_{Rs} = V_s - V_Z = 10 - 8 = 2 \, \text{V}

Now apply Ohm’s law to find R_s:

R_s = \frac{V_{Rs}}{I_{Z_{max}}} = \frac{2}{0.2} = 10 \, \Omega

Thus, the value of resistance R_s for safe operation is 10 Ω.