Q.

In the given circuit if the power rating of Zener diode is 10 mW, the value of series resistance Rs to regulate the input unregulated supply is             [2024]

1 0.5   
2 10 Ω  
3  
4 10   

Ans.

(1)

Potential difference across Rs

V1=8-5=3V

Current through the load resistor

I=51×103=5 mA

Maximum current through Zener diode

Izmax.=105=2 mA

and minimum current through Zener diode

Izmin.=0

 Ismax.=5+2=7 mA

and Rsmin=V1Ismax.=37 kΩ

Similarly, Ismin.=5 mA

and Rsmax.=V1Ismin.=35 kΩ

 37 kΩ<Rs<35 kΩ