Question

In the voltage regulator circuit shown below, the reverse breakdown voltage of zener diode is 5 V and power dissipated across it is 100 mW. Find RS

(1) 120 Ω 

(2) 250 Ω 

(3) 1000 Ω 

(4) 1500 Ω

Answer 1

Correct option is (1) 120 Ω 

i₁₀₀₀ Ω = 5 mA

\(i_z = \frac {P}{V_z} = 20 m A\)

\(\therefore \,i_R = 25 \,mA\)

V_R = 3V

\(\therefore \,R = \frac {3}{25} \times 10 ^3 = 120 \Omega \)