Question

If the barrier potential of the diode shown in the given circuit is \(0.7\,\mathrm{V}\), then the value of the resistance \(R\) is

• A. \(220\,\Omega\)
• B. \(150\,\Omega\)
• C. \(70\,\Omega\)
• D. \(100\,\Omega\)

Hint:

For a forward-biased silicon diode, \[ \boxed{ V_D\approx0.7\,\mathrm{V} } \] and \[ \boxed{ R=\frac{V_{\text{supply}}-V_D}{I}. } \]

Answer 1

The Correct Option is D

Step 1: Determine the voltage across the resistor. The supply voltage is \[ V=2.2\,\mathrm{V}. \] The forward-biased diode drops \[ 0.7\,\mathrm{V}. \] Hence, the voltage across the resistor is \[ V_R = 2.2-0.7 = 1.5\,\mathrm{V}. \]

Step 2: Apply Ohm's law. Given current, \[ I=15\,\mathrm{mA} =0.015\,\mathrm{A}. \] Therefore, \[ R = \frac{V_R}{I} = \frac{1.5}{0.015} = 100\,\Omega. \] Hence, \[ \boxed{100\,\Omega} \] Therefore, \[ \boxed{(D)} \] is the correct answer.