Multiple choice

A Silicon PN junction diode under reverse bias has depletion region of width 10 m. The relative permittivity of Silicon, $\epsilon_r = 11.7$ and the permittivity of free space $\epsilon_0 = 8.85 \times 10^{-12} F/m$. The depletion capacitance of the diode per square metre is

  1. $100 \mu F$
  2. $10 \mu F$
  3. $1 \mu F$
  4. $20 \mu F$
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B Correct answer
Explanation

$C = \frac{\epsilon_0 \epsilon_r A}{d} \\ or \hspace{0.2cm} \frac{C}{A} = \frac{\epsilon_0 \epsilon_r}{d} = \frac{8.85 \times 10^{-12} \times 11.7}{10 \times 10^{-6}} = 10.35 \mu F$

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