Semiconductor Electronics

In the combination of the following gates the output Y can be written in terms of inputs A and B as [figure]

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

In a p-n junction diode, change in temperature due to heating

1. affects only reverse resistance
2. affects only forward resistance
3. does not affect resistance of p-n junction
4. affects the overall V - I characteristics of p-n junction

In the circuit shown in the figure, the input voltage Vi is 20 V, VBE = 0 and VCE = 0. The values of IB, IC and β are given by [figure]

1. IB = 40 , IC = 10 mA, β = 250
2. IB = 25 , IC = 5 mA, β = 200
3. IB = 20 , IC = 5 mA, β = 250
4. IB = 40 , IC = 5 mA, β = 125

The given electrical network is equivalent to [figure]

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

Which one of the following represents forward bias diode ?

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

In a common emitter transistor amplifier the audio signal voltage across the collector is 3 V. The resistance of collector is 3 k . If current gain is 100 and the base resistance is 2 k , the voltage and power gain of the amplifier is

1. 15 and 200
2. 150 and 15000
3. 20 and 2000
4. 200 and 1000

To get output 1 for the following circuit, the correct choice for the input is [figure]

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

Consider the junction diode as ideal. The value of current flowing through AB is [figure]

1. 10-1 A
2. 10-3 A
3. 0 A
4. 10-2 A

A npn transistor is connected in common emitter configuration in a given amplifier. A load resistance of 800 is connected in the collector circuit and the voltage drop across it is 0.8 V. If the current amplification factor is 0.96 and the input resistance of the circuit is 192 , the voltage gain and the power gain of the amplifier will respectively be

1. 4, 4
2. 4, 3.69
3. 4, 3.84
4. 3.69, 3.84

The given circuit has two ideal diodes connected as shown in the figure. The current flowing through the resistance R1 will be [figure]

1. 2.5 A
2. 10.0 A
3. 1.43 A
4. 3.13 A

What is the output Y in the following circuit, when all the three inputs A, B, C are first 0 and then 1? [figure]

1. 0, 1
2. 0, 0
3. 1, 0
4. 1, 1

For CE transistor amplifier, the audio signal voltage across the collector resistance of 2 k is 4 V. If the current amplification factor of the transistor is 100 and the base resistance is 1 k , then the input signal voltage is

1. 10 mV
2. 20 mV
3. 30 mV
4. 15 mV

In the given figure, a diode D is connected to an external resistance R = 100 Ω and an e.m.f. of 3.5 V. If the barrier potential developed across the diode is 0.5 V, the current in the circuit will be [figure]

1. 20 mA
2. 35 mA
3. 30 mA
4. 40 mA

The input signal given to a CE amplifier having a voltage gain of 150 is Vi = 2 (15t + 3 ). The corresponding output signal will be

1. 2 (15t + 5 6 )
2. 300 (15t + 4 3 )
3. 300 (15t + 3 )
4. 75 (15t + 2 3 )

Which logic gate is represented by the following combination of logic gates? [figure]

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

If in a p-n junction, a square input signal of 10 V is applied, as shown, [figure] then the output across RL will be

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

The given graph represents V-I characteristic for a semiconductor device. [figure] Which of the following statement is correct ?

1. It is V-I characteristic for solar cell where, point A represents open circuit voltage and point B short circuit current.
2. It is for a solar cell and points A and B represent open circuit voltage and current, respectively.
3. It is for a photodiode and points A and B represent open circuit voltage and current, respectively.
4. It is for a LED and points A and B represent open circuit voltage and short circuit current, respectively.

The barrier potential of a p-n junction depends on Which one of the following is correct ?

1. A and B only
2. B only
3. B and C only
4. A, B and C

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.

The figure shows a logic circuit with two inputs A and B and the output C. The voltage wave forms across A, B and C are as given. The logic circuit gate is [figure]

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

In a CE transistor amplifier, the audio signal voltage across the collector resistance of 2 k is 2 V. If the base resistance is 1 k and the current amplification of the transistor is 100, the input signal voltage is

1. 0.1 V
2. 1.0 V
3. 1 mV
4. 10 mV