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
$$\left(\text{A}\right)2037.6\times {10}^{-3}$$ amp
$$\left(\text{B}\right)203.76\times {10}^{-3}$$ amp
$$\left(\text{C}\right)20.376\times {10}^{-3}$$ amp
$$\left(\text{D}\right)2.0376\times {10}^3$$ 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,$$i_s={10}^{-5}amp$$, $$T={27}^{0}C$$= $(273+27)$$k=300K$, $$v=0.2V$$
Now using the values and formula we get that $\text{i = }{\text{i}}_{\text{s}}({\text{e}}^{\text{ev/kT}}-1)$
$\Rightarrow i={10}^{-5}\left[{\text{e}}^{{\displaystyle \frac{1.6\times \text{1}{\text{0}}^{-19}\times \text{0}\text{.2}}{1.4\times \text{1}{\text{0}}^{-23}\times \text{300}}}-1}\right]$
$\Rightarrow i={10}^{-5}\left[{\text{e}}^{{\displaystyle \frac{0.32\times \text{1}{\text{0}}^{-19}}{420\times \text{1}{\text{0}}^{-23}}}-1}\right]$
$\Rightarrow i={10}^{-5}[2038.6-1]$
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.