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Concepts Of Physics MCQ Edition [Volume 2]PhysicsSemiconductors and Semiconductor Devices

When a p - n junction is reverse-biased, the current is nearly constant at 25 A . Upon being forward-biased at 200 mV , a current of 75 A is observed. Find the magnitude of the diffusion current when the diode is unbiased.

Options

  1. A0
  2. B25 A
  3. C75 A
  4. D50 A

Correct answer

B. 25 A

Step-by-step solution

In a p - n junction diode, the net current is the difference between the diffusion current and the drift current. The drift current is due to the flow of minority charge carriers and is relatively independent of the applied bias voltage. It is equal to the reverse saturation current. Given that the reverse-biased current is 25 A , the drift current is I_ drift = 25 A . When the diode is unbiased, the net current through the junction is zero. I_ net = I_ diffusion - I_ drift = 0 I_ diffusion = I_ drift = 25 A

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