Question

A silicon diode has a forward voltage drop of $1.2V$ for a forward DC current of $100mA$ . It has a reverse current of $10^{- 6}mA$ for a reverse voltage of $10V$ . The bulk and reverse resistances of diode are :-

• A. $5 \Omega, 10 \mathrm{M} \Omega$
• B. $6 \Omega, 6 M\Omega$
• C. $7 \Omega, 70 \mathrm{M} \Omega$
• D. $5 \Omega, 1 \mathrm{M} \Omega$

Answer 1

Answer: (A)

For a silicon diode, forbidden gap is of the order of $0.7 \mathrm{V}$
$\because$ Bulk resistance $=\frac{(1.2-0.7) \mathrm{V}}{100 \times 10^{-3} \mathrm{A}}$
$=0.5 \times 10 \Omega$
$=5 \Omega$
Reverse resistance $=\frac{10 \mathrm{V}}{1 \times 10^{-6} \mathrm{A}}=10 \mathrm{M} \Omega$