Question

The diode used in the circuit shown in the figure has a constant voltage drop at 0.5 V at all currents and a maximum power rating of 100 milli watts.
What should be the value of the resistor R, connected in series with diode, for obtaining maximum current?

• A. $6.76\Omega$
• B. $20\Omega$
• C. $5\Omega$
• D. $5.6\Omega$

Answer 1

The correct option is C $5\Omega$

$As{R}_D=\frac{V^{2}D}{P_D}=\frac{(0.5V{)}^2}{0.1W}=2.5\Omega$
$I_D=\frac{V_D}{R_D}=0.2A$
Total resistance required in the circuit,
$R_{eq}=\frac{V}{I_D}=\frac{1.5}{0.2}=7.5\Omega$
Resistance of the series resistor, $R=R_{eq}-R_D=7.5-2.5=5\Omega$