Question

The V − I characteristic of a silicon diode is as shown in the figure. Calculate the resistance of the diode at (i) I = 15 mA and (ii) V= −10 V.

Answer 1

(i) From the given curve, we have
voltage, V = 0.8 volt for current, I = 20 mA
voltage​,​V = 0.7 volt for current​, I = 10 mA

\[\Rightarrow \Delta I = (20 - 10) mA = 10 \times {10}^{- 3} A\]

\[ \Rightarrow \Delta V = (0 . 8 - 0 . 7) = 0 . 1 V\]

\[ \therefore \text { Resistance, } R = \frac{\Delta V}{\Delta I}\]

\[ \Rightarrow R = \frac{0 . 1}{10 \times {10}^{- 3}}\]

\[ \Rightarrow R = 10 \Omega\]

(ii) \[For V = - 10 V, we have\]

\[ I = - 1 \mu A = 1 \times {10}^{- 6} A\]

\[ \Rightarrow R = \frac{10}{1 \times {10}^{- 6}} = 1 . 0 \times {10}^7 \Omega\]