Question

A Zener diode of power rating 1 W is to be used as a voltage regulator. If Zener has a breakdown of 5 V and it has to regulate voltage which fluctuated between 3 V and 7 V, what should be the value of $R_S$ for safe operation?

• A. $5\Omega$
• B. $10\Omega$
• C. $15\Omega$
• D. $20\Omega$

Answer 1

The correct option is B $10\Omega$

Power rating, $P=1W$, $V_z=5V$ ,

We have to find

$R_s$ ,$Vs=3Vto7V$

$I_{Z}max$ = $\frac{P}{V_Z}=\frac{1}{5}=0.2A$

$R_s=\frac{V_S-V_z}{I_{Z}max}=\frac{7-5}{0.2}=10\Omega$