GATE 2024 EC – Question 65
The photocurrent of a PN junction diode solar cell is 1 mA. The voltage corresponding to its maximum power point is 0.3 V. If the thermal voltage is 30 mV, the reverse saturation current of the diode (in nA, rounded off to two decimal places) is ______.
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Correct answer: 4.11 to 4.15
Explanation
$I=I_L-I_0(e^{V/V_T}-1)$ and the maximum-power condition $d(VI)/dV=0$ gives $I_m=I_0\dfrac{V_m}{V_T}e^{V_m/V_T}$. With $V_m/V_T=10$: $I_L=I_m+I_0(e^{10}-1)=I_0(11e^{10}-1)$. So $I_0=\dfrac{1\text{ mA}}{11\times22026.47-1}=4.13\times10^{-9}$ A $=4.13$ nA.