Semi conductor devices practice · Medium

Option A is correct because a NOT gate, also known as an inverter, performs the logical operation of inverting the input signal.

Option D ($81.2\mathrm{ }\%$) is correct because the maximum efficiency of a full-wave rectifier is 81.2%.

Option B (Gallium to pure silicon) is correct because adding a trivalent impurity like Gallium to silicon creates a P-type semiconductor with holes as the majority charge carriers.

Option A (It has no charge carriers) is correct because the depletion layer is formed by the diffusion of charge carriers, leaving behind a region devoid of mobile charges.

Option D (Emitter-base depletion layer is small but base-collector depletion layer is large) is correct because in a properly biased transistor, the emitter-base junction is forward biased (small depletion layer) and the base-collector junction is reverse biased (large depletion layer).

Option D is correct because the conductivity of a semiconductor increases with temperature due to a significant increase in the number density of current carriers, despite a decrease in relaxation time.

Option B ($2 \times {10^6}$) is correct because the reverse bias resistance is calculated by dividing the change in voltage by the change in current.

Option B (If both assertion and reason are true but reason is not the correct explanation of assertion) is correct because both the photodiode working in reverse bias and the increase in diode current with light intensity are true, but the latter doesn't explain the former.

Option A ($5.3 \times 10^{28}, 2.65 \times 10^{28}$) is correct because it calculates the total number of states and the number of unoccupied states in the 3s band of sodium, based on its density and atomic mass.

Option A is correct. The sudden increase in current in a Zener diode occurs due to the rupture of covalent bonds in the depletion region under high reverse voltage.

Option D ($A + B$) is correct because, according to De Morgan's theorem, the complement of the product of complements is the sum of the variables.

Option B ($3\,k\Omega$) is correct because the collector resistance is calculated using the voltage gain, beta, and input resistance of the common emitter amplifier.

Option D (OR gate) is correct because the Boolean expression ${P}+\overline{{P}} {Q}$ simplifies to ${P} + {Q}$, which is the OR operation.

Option C (An ideal diode is an open switch) is correct because an ideal diode acts as a closed switch in forward bias and an open switch in reverse bias.

Option B ($48.2\%$) is correct because the ripple factor for a full-wave rectifier is approximately 0.482, which is equivalent to 48.2%.

Option D (0.48, 81.2 %) is correct because these are the standard ripple factor and efficiency values for a full-wave rectifier.

Option D (Zero) is correct because the cross product of two vectors results in a vector perpendicular to both, and the dot product of perpendicular vectors is zero.

Option A (Statement I is true, Statement II is true; Statement II is the correct explanation for Statement I) is correct because Zener diodes are used as voltage regulators due to their ability to maintain constant voltage under reverse bias.

The correct answer is D (Emitter is heavily doped, collector is moderately doped and base is lightly doped) because this configuration optimizes transistor performance.

Option A is correct because both statements are true: n-type semiconductors have higher conduction current due to higher electron mobility compared to holes in p-type semiconductors.

Option B (120 Hz) is correct. In half-wave rectification, the output frequency is the same as the input frequency.

Option D ($\mathrm{\beta }$ is positive and magnitude of $\mathrm{\beta } = 1/A$) is correct because the Barkhausen criterion for oscillation requires positive feedback and a loop gain of unity (Aβ = 1).

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.