Semiconductor Electronics

In a n-type semiconductor, which of the following statements is true?

1. Holes are minority carriers and pentavalent atoms are dopants.
2. Holes are majority carriers and trivalent atoms are dopants.
3. Electrons are majority carriers and trivalent atoms are dopants.
4. Electrons are minority carriers and pentavalent atoms are dopants.

The output (X) of the logic circuit shown in figure will be [figure]

1. X = A . B
2. X = A + B
3. X = A . B
4. X = A . B

In a common emitter (CE) amplifier having a voltage gain G, the transistor used has transconductance 0.03 mho and current gain 25. If the above transistor is replaced with another one with transconductance 0.02 mho and current gain 20, the voltage gain will be

1. 13G
2. 54G
3. 23G
4. 1.5G

The output from a NAND gate is divided into two in parallel and fed to another NAND gate. The resulting gate is a [figure]

1. AND gate
2. NOR gate
3. OR gate
4. NOT gate

In an unbiased p-n junction, holes diffuse from the p-region to n-region because of

1. The attraction of free electrons of n-region.
2. The higher hole concentration in p-region than that in n-region.
3. The higher concentration of electrons in the n-region than that in the p-region.
4. The potential difference across the p-n junction.

One way in which the operation of an n-p-n transistor differs from that of a p-n-p is

1. The emitter junction injects minority carriers into the base region of the p-n-p
2. The emitter injects holes into the base of the p-n-p and electrons into the base region of n-p-n
3. The emitter injects holes into the base of n-p-n
4. The emitter junction is reverse biased in n-p-n

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

The input resistance of a silicon transistor is 100 . Base current is changed by 40 which results in a change in collector current by 2 mA. This transistor is used as a common emitter amplifier with a load resistance of 4 k . The voltage gain of the amplifier is

1. 2000
2. 3000
3. 4000
4. 1000

Two ideal diodes are connected to a battery as shown in the circuit. The current supplied by the battery is [figure]

1. 0.75 A
2. zero
3. 0.25 A
4. 0.5 A

C and Si both have same lattice structure; having 4 bonding electrons in each. However, C is insulator whereas Si is intrinsic semiconductor. This is because

1. In case of C the valence band is not completely filled at absolute zero temperature.
2. In case of C the conduction band is partly filled even at absolute zero temperature.
3. The four bonding electrons in the case of C lie in the second orbit, whereas in the case of Si they lie in the third.
4. The four bonding electrons in the case of C lie in the third orbit, whereas for Si they lie in the fourth orbit.