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