A zener diode of power rating 2 W is to be used as a voltage regulator. If the zener diode has a bre

Question

A zener diode of power rating 2 W is to be used as a voltage regulator. If the zener diode has a breakdown of 10 V and it has to regulate voltage fluctuated between 6 V and 14 V , the value of $R_{S}$ for safe operation should be\ ________ $\Omega$.\

Professor PC Thomas Classes · Answer

(20) : Given that,\ $P=2 \mathrm{~W}, V_{Z}=10 \mathrm{~V}$\ Current in the zener diode,\ $I=\frac{P}{V_{Z}}=\frac{2}{10}=0.2 \mathrm{~A}$\ For $V_{S}=14 \mathrm{~V}$, voltage drop across $R_{L}, V=$ $14-10=4 \mathrm{~V}$\ Using Ohm's law, $V=I R_{S}$\ $	herefore \quad R_{S}=\frac{V}{I}=\frac{4}{0.2}=20 \Omega$\