Question

What is the non linear $V-I$ relation in a pn Junction in forward bias?

• A. $I=I_s{e}^{V/V_T}$
• B. $I=I_s(e^{V/V_T}-1)$
• C. $I=I_s(1-e^{V/V_T})$
• D. $I=I_s{\left(\frac{V}{V_0}\right)}^{\frac{3}{2}}$

Answer 1

The correct option is B $I=I_s(e^{V/V_T}-1)$

Since the P-N junction diode's resistance changes according to the direction of current flow just above the zero bias, hence it is called a non linear device. The current depends on the applied voltage. The relation between voltage and current is exponential, it is expressed as
$I=I_s[e^{\left(\frac{V}{\eta V_T}\right)}-1]$
where, $I_s$ is the reverse saturation current
$\eta$ is 1 for germanium and 2 for silicon.
V is the applied voltage.
$V_T$ is the voltage equivalent of the temperature.
Therefore for germanium diode.
$I=I_s[e^{\left(\frac{V}{V_T}\right)}-1]$