Question

In PN- junction diodes the reverse saturation current is \[{10^{ - 5}}\] amp at \[{27^0}C\]. The forward current for a voltage of \[0.2\] volt is
\[\left( {\text{A}} \right){\text{ }}2037.6 \times {10^{ - 3}}\] amp
\[\left( {\text{B}} \right){\text{ }}203.76 \times {10^{ - 3}}\] amp
\[\left( {\text{C}} \right){\text{ }}20.376 \times {10^{ - 3}}\] amp
\[\left( {\text{D}} \right){\text{ }}2.0376 \times {10^3}\] amp

Answer 1

Hint: Diode: It is a two-terminal electronic device that produces current primarily in one direction; it has low resistance in one direction and high resistance in other direction.
P-type semiconductor: Trivalent impurity (Boron, Gallium, Indium, and Aluminum) is added to an intrinsic or pure semiconductor (Silicon, Germanium).
N-type semiconductor: Pentavalent impurity (Arsenic, Antimony, and Phosphorus) is added to an intrinsic or pure semiconductor (Silicon, Germanium).
PN-junction: It is formed when a p-type semiconductor is fused to an n-type semiconductor.

Formula used:
${\text{i = }}{{\text{i}}_{\text{s}}}({{\text{e}}^{{\text{ev/kT}}}} - 1)$,
Here \[i = \] forward current in the PN-junction, \[{i_s} = \] saturation current in the PN-junction,
\[e = \] Charge of the electron,\[\;v = \] voltage source, \[k = \] Boltzmann’s constant, \[T = \] absolute temperature

Complete step by step answer:
It is given that the question,\[{i_s} = {\text{ }}{10^{ - 5}}amp\], \[T = {\text{ }}{27^0}C\]= $(273 + 27)$$k = 300K$, \[v = 0.2V\]
Now using the values and formula we get that ${\text{i = }}{{\text{i}}_{\text{s}}}({{\text{e}}^{{\text{ev/kT}}}} - 1)$
$\Rightarrow i= {10^{ - 5}}\left[ {{{\text{e}}^{\dfrac{{1.6 \times {\text{1}}{{\text{0}}^{ - 19}} \times {\text{0}}{\text{.2}}}}{{1.4 \times {\text{1}}{{\text{0}}^{ - 23}} \times {\text{300}}}} - 1}}} \right]$
$\Rightarrow i= {10^{ - 5}}\left[ {{{\text{e}}^{\dfrac{{0.32 \times {\text{1}}{{\text{0}}^{ - 19}}}}{{420 \times {\text{1}}{{\text{0}}^{ - 23}}}} - 1}}} \right]$
$\Rightarrow i= {10^{ - 5}}[2038.6 - 1]$
On some simplification we get,
$\Rightarrow i = 20.376 \times {\text{1}}{{\text{0}}^{ - 3}}$A

Hence the correct option is \[\left( {\text{C}} \right)\].

Note:
Forward current: If the electrical current flows in the direction of lower resistance in a diode is called forward current.
A certain amount of positive voltage to be applied across the PN-junction to perform forward current.
A steady or equilibrium stage will be reached whereby electrons are diffusing out of the N-region and drifting (pulling by the huge positive charge left behind) back in at the same rate.
PN-junction is used in solar cells, a forward-biased diode is used in LED, and it is also used in rectifiers in many electric circuits.
In a PN-junction diode, the reverse saturation current is due to the diffusive flow of minority electrons from the p-side to the n-side and the holes move from the n-side to the p-side.