Question

A zener diode having breakdown voltage equation to 15 V is used in voltage regulator circus shown in figure the current through diode is :

• A. 100 mA
• B. 95 mA
• C. 150 mA
• D. 195 mA

Answer 1

Answer: (B)

95 mA

The current through the load resistance, $I_1=\frac{V_{zener}}{R_{Load}}=\frac{5}{1\times {10}^3}=5\times {10}^{-3}A$

The current through the $150\Omega$ resistance, $I_2=\frac{E-V_{zener}}{R}=\frac{(20-5)}{150}=\frac{15}{150}=0.1A$

Clearly, the Zener current, $I_{zener}=I_2-I_1=[0.1-(5\times {10}^{-3})]A=95mA$

Option (B) is correct.