Question

The above $I-V$ graph shows the characteristics of a $p-n$ junction diode which is connected to a signal generator of the peak voltage $22V$ . The dc current across the load $4.8\Omega$ is $iA$ , then $4i=?$

Answer 1

The current at $2V$ is $250mA$ and at $2.2V$ it is
$500mA.$ The dynamic resistance in this region is,
$r_{d}=\frac{\Delta V}{\Delta I}$
$=\frac{\left(\right. 2 . 2 - 2 \left.\right)}{\left(\right. 500 - 250 \left.\right) \times \left(10\right)^{- 3}}=\frac{4}{5}\Omega$
Now, when the diode is connected to ac supply it works as a half-wave rectifier giving a dc output. For half-wave rectifier, peak current is,
$I_{0}=\frac{V_{0}}{r_{d} + R_{L}}$
$=\frac{22}{\frac{4}{5} + 4 . 8}$
$=\frac{22}{5 . 6}A$
$\therefore I_{d c}=\frac{I_{0}}{\pi }=\frac{22}{5 . 6 \times \frac{22}{7}}$
$=\frac{5}{4}$
$=1.25A$