Question

A Zener diode, having breakdown voltage equal to $15V$, is used in a voltage regulator circuit shown in figure. The current through the diode is

• A. $10mA$
• B. $15mA$
• C. $20mA$
• D. $5mA$

Answer 1

Answer: (D)

$5mA$

Voltage across zener diode is constant
${\left(i\right)}_{1k\Omega }=\frac{15V}{1k\Omega }=15mA$

${\left(i\right)}_{250\Omega }=\frac{(20-15)V}{250\Omega }=\frac{5V}{250\Omega }=\frac{20}{1000}A=20mA$

$\therefore {\left(i\right)}_{Zener}=(20-15)=5mA$.