Question

A zener diode in the circuit shown has a knee current of $5mA$ and a maximum allowed power dissipation of $300mW.$ What are the minimum and maximum load currents that can be drawn safely from the circuit, keeping the output voltage $V_{0}$ constant at 6 volts ?

• A. $0mA,180mA$
• B. $5mA,110mA$
• C. $10mA,55mA$
• D. $60mA,180mA$

Answer 1

Answer: (C)

Current from source is $I=\left(\right.9-6\left.\right)/50=.06A$
$=60mA$
Now, $I_{z m i n}=5mA$ and
$I_{z m a x}=P_{m a x}/Vz=300mW/6V=50mA$
So, $L_{m a x}=I-I_{z m i n}=60mA-5mA=55mA$
And $L_{m i n}=I-I_{z m a x}=60mA-50mA-50mA$
$=10$