question_answer

A Zener diode of power rating 1W is to be used as a voltage regulator. If Zener diode has a breakdown voltage of 5V and it has to regulate a voltage which is fluctuated between 3V and 7V, what should be the value of resistance \[{{R}_{S}},\] for safe operation as shown in the figure given below?

Answer:

Given, power, P = 1W Zener breakdown voltage, \[{{v}_{z}}=5V\] Minimum voltage, \[{{V}_{min}}=3V\] Maximum voltage, \[{{V}_{\max }}=7V\] Current, \[{{l}_{z\max }}=\frac{P}{{{V}_{Z}}}=\frac{1}{5}=0.2A\] The value of R for safe operation, \[{{R}_{Z}}=\frac{{{V}_{\max }}-{{V}_{z}}}{{{l}_{z\max }}}=\frac{7-5}{0.20}=\frac{2}{0.2}\] \[{{R}_{z}}=10\,\Omega \]