Question

I-V characteristic curve of a diode in a forward bias is given in figure. Find out dynamic resistance.

• A. $212·3\Omega$
• B. $205·3\Omega$
• C. $245·3\Omega$
• D. $233·3\Omega$

Answer 1

The correct option is D

$233·3\Omega$

Step 1: Given data

1. The change in voltage $\mathrm{dV}=0·7\mathrm{V}$
2. The change in current $\mathrm{dI}=3\mathrm{mA}=3\times {10}^{-3}\mathrm{A}$
3. 

Step 2: Formula used

1. Dynamic resistance is the measure of a small change in voltage to a small change in current that is-

${\mathrm{r}}_{\mathrm{d}}\left(\mathrm{dynamic}\mathrm{resistance}\right)=\frac{\mathrm{dV}}{\mathrm{dI}}=\frac{\mathrm{small}\mathrm{change}\mathrm{in}\mathrm{voltage}}{\mathrm{small}\mathrm{change}\mathrm{in}\mathrm{current}}$

Step 3: Calculate the dynamic resistance in the given case

The dynamic resistance can be calculated as,

$\begin{array}{rcl}{\mathrm{r}}_{\mathrm{d}}& =& \frac{0·7\mathrm{V}}{3\times {10}^{-3}\mathrm{A}}\\ & =& 0·2333\times {10}^3\mathrm{\Omega }\\ & =& 233·3\mathrm{\Omega }\end{array}$

Thus, the dynamic resistance is $233·3\mathrm{\Omega }$

Hence, option D is the correct answer.