Question

The following table provides the set of values of $V$ and $I$ obtained for a given diode. Let the characteristics $\alpha$ be nearly linear, over this range, the forward and reverse bias resistance of the given diode respectively are

	$V$	$I$
Forward biasing	$2.0V$	$60mA$
	$2.4V$	$60mA$
Reverse biasing	$0.V$	$60mA$
	$-2V$	$60mA$

• A. $10\Omega ,8\times 10^6\Omega$
• B. $20\Omega ,\times 10^5\Omega$
• C. $20\Omega ,8\times 10^6\Omega$
• D. $10\Omega ,10\Omega$

Answer 1

Answer: (C)

For forward biasing,
$\Delta V=2.4-2.0=0.4V$
$\Delta I=80-60=20mA$
$\therefore r_{fb}=\frac{\Delta V}{\Delta I}$
$=\frac{0.4}{20\times 10^{-3}}=20\Omega$
For reverse biasing,
$\Delta V=-2-0=-2V$
$\Delta I=-0.25-0=-0.25\mu A$
$r_{rb}=\frac{-2}{-0.25\times 10^{-6}}$
$=8\times 10^6\Omega$