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	60 mA
	2.4V	80 m A
Reverse biasing	0V	0μA
	− 2V	− 0.25μA

• A. $10\Omega,8 \times 10^{6}\Omega$
• B. $20\Omega,4 \times 10^{5}\Omega$
• C. $20\Omega,8 \times 10^{6}\Omega$
• D. $10\Omega,10\Omega$

Answer 1

Answer: (C)

$20\Omega,8 \times 10^{6}\Omega$

Answer 2

: 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

$\Delta V = - 2 - 0 = - 2V$

}{r_{rb} = \frac{- 2}{- 0.25 \times 10^{- 6}} = 8 \times 10^{6}\Omega}$$