Semi conductor devices practice · Mixed difficulty

Option A ($8.01 \times 10^{15} \mathrm{~cm}^{-3}$) is correct because the number density of donor atoms is calculated using the conductivity, electron charge, and electron mobility.

Option A (20) is correct because the current gain is the ratio of change in collector current to the change in base current.

Option D (50) is correct because the current gain is the ratio of change in collector current to the change in base current.

Option B (A =1, B = 1) is correct because an AND gate produces an output of 1 only when all its inputs are 1.

Option D is correct because at absolute zero temperature, a semiconductor behaves like an insulator, not a conductor.

Option D (Infrared rays) is correct because GaAs with a band gap of 1.5 eV emits photons in the infrared region.

Option B is correct because as temperature increases in a semiconductor, more charge carriers are generated (n increases), but their average drift speed (v) decreases due to increased collisions.

Option D (None of these) is incorrect and the correct answer is that the current is approximately zero due to the depletion region, but there is a very small current due to thermally generated carriers. Since none of the options perfectly describe this, the closest is that the current is approximately zero because the charge carriers do not move freely due to the depletion region.

Option D (60 Hz) is correct because in half-wave rectification, the output frequency is the same as the input frequency.

Option A (If both statements are correct) is correct because metals have a positive temperature coefficient and semiconductors have a negative temperature coefficient of resistance.