Semiconductor Electronics

Pure Si at 500 K has equal number of electron (ne) and hole (nh) concentrations of 1.5 1016 m-3. Doping by indium increases nh to 4.5 1022 m-3. The doped semiconductor is of

1. p-type having electron concentration ne = 5 109 m-3
2. n-type with electron concentration ne = 5 1022 m-3
3. p-type with electron concentration ne = 2.5 1010 m-3
4. n-type with electron concentration ne = 2.5 1023 m-3

In forward biasing of the p-n junction

1. the positive terminal of the battery is connected to p-side and the depletion region becomes thick.
2. the positive terminal of the battery is connected to n-side and the depletion region becomes thin.
3. the positive terminal of the battery is connected to n-side and the depletion region becomes thick.
4. the positive terminal of the battery is connected to p-side and the depletion region becomes thin.

Symbolic representations of four logic gates are shown as [figure] Pick out which ones are for AND, NAND and NOT gates, respectively

1. (ii), (iii) and (iv)
2. (iii), (ii) and (i)
3. (iii), (ii) and (iv)
4. (iii), (iv) and (ii)

If a small amount of antimony is added to germanium crystal

1. it becomes a p-type semiconductor
2. the antimony becomes an acceptor atom
3. there will be more free electrons than holes in the semiconductor
4. its resistance is increased

A transistor is operated in common emitter configuration at VC = 2 V such that a change in the base current from 100 A to 300 A produces a change in the collector current from 10 mA to 20 mA. The current gain is

1. 50
2. 75
3. 100
4. 25

The following figure shows a logic gate circuit with two inputs A and B and the output Y. The voltage waveforms of A, B and Y are as given. [figure] The logic gate is

1. NOR gate
2. OR gate
3. AND gate
4. NAND gate

For transistor action Which one of the following pairs of statements is correct?

1. D and A
2. A and B
3. B and C
4. C and D

To get an output Y = 1 in given circuit which of the following input will be correct? [figure]

1. A 1, B 0, C 0
2. A 1, B 0, C 1
3. A 1, B 1, C 0
4. A 0, B 1, C 0

Which one of the following statements is false?

1. Pure Si doped with trivalent impurities gives a p-type semiconductor.
2. Majority carriers in a n-type semiconductor are holes.
3. Minority carriers in a p-type semiconductor are electrons.
4. The resistance of intrinsic semiconductor decreases with increase of temperature.

Which one of the following bonds produces a solid that reflects light in the visible region and whose electrical conductivity decreases with temperature and has high melting point?

1. metallic bonding
2. van der Waals' bonding
3. ionic bonding
4. covalent bonding