Question 222: Semiconductors and Logic Gates

Question

A zener of breakdown voltage V
z
= 8 V and maximum zener current, I
ZM
= 10 mA is subjectd to an input voltage V
i
= 10 V with series resistance R = 100 $$\Omega$$. In the given circuit R
L
represents the variable load resistance. The ratio of maximum and minimum value of R
L
is _____________.

Accepted Answer

Minimum value of R
L
for which the diode is shorted is $${{{R_L}} \over {{R_L} + 100}} 	imes 10 = 8 \Rightarrow {R_L} = 400\,\Omega $$
For maximum value of R
L
, current through diode is 10 mA
So $${i_R} = {i_{{R_L}}} + {I_{ZM}}$$
$${2 \over {100}} = {8 \over {{R_L}}} + 10 	imes {10^{ - 3}}$$
$$10 	imes {10^{ - 3}} = {8 \over {{R_L}}}$$
$${R_L} = 800\,\Omega $$
So $${{{R_{L\,\max }}} \over {{R_{L\,\min }}}} = 2$$

Semiconductors and Logic Gates

A zener of breakdown voltage V z = 8 V and maximum zener current, I ZM = 10 mA is subjectd to an input voltage V i = 10 V with series resistance R = 100 $\Omega$. In the given circuit R L represents the variable load resistance. The ratio of maximum and minimum value of R L is _____________.

Integer / Numeric Answer Type