A p-n junction diode has a potential barrier of 0.5 V. If 1.5 V battery is used to forward bias the diode, the minimum value of resistance that must be used in series with the diode so that the maximum current does not exceed 5 mA, will be
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 200 Ω
In forward bias, a voltage equal to the barrier potential drops across the diode itself; the rest of the battery voltage drops across the series resistor.
\( \displaystyle V_R = 1.5\,\mathrm{V} - 0.5\,\mathrm{V} = 1.0\,\mathrm{V} \)
The current must not exceed \( 5\,\mathrm{mA} = 5\times10^{-3}\,\mathrm{A} \), so
\( \displaystyle R_{\mathrm{min}} = \frac{V_R}{I_{\mathrm{max}}} = \frac{1.0\,\mathrm{V}}{5\times10^{-3}\,\mathrm{A}} = 200\,\Omega \)