Semiconductor Electronics

Transfer characteristics [output voltage (V0) vs input voltage (Vi)] for a base biased transistor in CE configuration is as shown in the figure. For using transistor as a switch, it is used [figure]

1. in region III
2. both in region (I) and (III)
3. in region II
4. in region I

A Zener diode, having breakdown voltage equal to 15 V, is used in a voltage regulator circuit shown in figure. The current through the diode is [figure]

1. 5 mA
2. 10 mA
3. 15 mA
4. 20 mA

In the following figure, the diodes which are forward biased, are [figure]

1. (A), (B) and (D)
2. (C) only
3. (C) and (A)
4. (B) and (D)

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

The device that can act as a complete electronic circuit is

1. junction diode
2. integrated circuit
3. junction transistor
4. zener diode

A common emitter amplifier has a voltage gain of 50, an input impedance of 100 and an output impedance of 200 . The power gain of the amplifier is

1. 500
2. 1000
3. 1250
4. 50

A p-n photodiode is fabricated from a semiconductor with a band gap of 2.5 eV. It can detect a signal of wavelength

1. 4000 nm
2. 6000 nm
3. 4000 A
4. 6000 A

The symbolic representation of four logic gates are given below [figure] The logic symbols for OR, NOT and NAND gates are respectively

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

A transistor is operated in common-emitter configuration at VC = 2 V such that a change in the base current from 100 to 200 produces a change in the collector current from 5 mA to 10 mA. The current gain is

1. 100
2. 150
3. 50
4. 75

A p-n photodiode is made of a material with a band gap of 2.0 eV. The minimum frequency of the radiation that can be absorbed by the material is nearly

1. 1 1014 Hz
2. 20 1014 Hz
3. 10 1014 Hz
4. 5 1014 Hz

The voltage gain of an amplifier with 9% negative feedback is 10. The voltage gain without feedback will be

1. 1.25
2. 100
3. 90
4. 10

Which one of the following represents forward bias diode?

1. [figure]
2. [figure]
3. [figure]
4. [figure]

In the following circuit, the output Y for all possible inputs A and B is expressed by the truth table. [figure]

1. [figure]
2. [figure]
3. [figure]
4. [figure]

In the energy band diagram of a material shown below, the open circles and filled circles denote holes and electrons respectively. The material is [figure]

1. an insulator
2. a metal
3. an n-type semiconductor
4. a p-type semiconductor

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

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

Which one of the following represents forward bias diode ?

1. [figure]
2. [figure]
3. [figure]
4. [figure]

A transistor is operated in common emitter configuration at constant collector voltage VC = 1.5 V such that a change in the base current from 100 to 150 produces a change in the collector current from 5 mA to 10 mA. The current gain is

1. 50
2. 67
3. 75
4. 100

Choose the only false statement from the following.

1. In conductors the valence and conduction bands overlap.
2. Substances with energy gap of the order of 10 eV are insulators.
3. The resistivity of a semiconductor increases with increase in temperature.
4. The conductivity of a semiconductor increases with increase in temperature.

Zener diode is used for

1. amplification
2. rectification
3. stabilisation
4. producing oscillations in an oscillator.

Application of a forward bias to a p-n junction

1. widens the depletion zone
2. increases the potential difference across the depletion zone
3. increases the number of donors on the n side
4. decreases the electric field in the depletion zone.

Carbon, silicon and germanium atoms have four valence electrons each. Their valence and conduction bands are separated by energy band gaps represented by (Eg)C, (Eg)Si and (Eg)Ge respectively. Which one of the following relationships is true in their case?

1. (Eg)C > (Eg)Si
2. (Eg)C < (Eg)Si
3. (Eg)C = (Eg)Si
4. (Eg)C < (Eg)Ge.