Semiconductor Electronics: Materials, Devices and Simple Circuits Test 37

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Semiconductor Electronics: Materials, Devices and Simple Circuits Test 37

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Question 1
1 / -0

To get an OR gate from a NAND gate, we need

A
Only two NAND gates

B
Two NOT gates obtained from NAND gates and one NAND gate

C
Four NAND gates and two AND gates obtained from NAND gates

D
None of the above

Solution

To obtain OR gate from NAND gates we need to NOT gates obtained from NAND gates and one NAND gate as figure.
Boolean expression $$Y=\overline{A.B.}=\overline{A}+\overline{B}$$
$$=A+B,$$ $$OR$$ gate
Question 2
1 / -0

For what value of A, B and C. The output of Y=1

A
0 0 1

B
1 0 1

C
1 0 0

D
0 1 0

Solution

Clearly,
$$Y=( A+B ). C=( A.C ) + ( B.C )$$
For
$$A=0, B=0\, \& \,C=1$$, $$Y=( 0.1 ) + ( 0.1 ) = 0$$
$$A=1, B=0\, \& \,C=1$$, $$Y=( 1.1 ) + ( 0.1 ) = 1$$
$$A=1, B=0\, \& \,C=0$$, $$Y=( 0.1 ) + ( 0.0 ) = 0$$
$$A=0, B=1\, \& \,C=0$$, $$Y=( 0.0 ) + ( 1.0 ) = 0$$
So, option ( b ) is correct.
Question 3
1 / -0

The energy gap between the valence band and the conduction band for the material is $$>9eV$$. Identify the material.

A
An insulator

B
A metal

C
An intrinsic semiconductor

D
A superconductor

Solution

The energy gap is the difference between energies corresponding to the electrons valance band and conduction band.
Free electrons present in conduction band, conducts the energy in the materials.
In metals, valance band and conduction bands overlaps with each other.
In semiconductors, energy gap is small, i.e. when temperature rises, the excited electrons can achieve conduction band.
In insulators, the energy gap is more than 5eV, i.e. if temperature rises higher the valance electrons are not able to achieve conduction band.
Therefore, the given material is an insulator.
Hence, correct answer is option A.
Question 4
1 / -0

Which of the following logic gates considered as universal?

A

B

C

D

Solution

NAND gate is considered as the universal gate because all other logic gates can be formed using NAND gate.
The symbol of NAND gate is given in option B.
Question 5
1 / -0

In an unbiased $$p-n$$ junction

A
Potential at $$p$$ is more than that at $$n$$

B
Potential at $$p$$ is less than that at $$n$$

C
Potential at $$p$$ is equal to that at $$n$$

D
Potential at $$p$$ is +ve and that at $$n$$ is -ve

Solution

Holes from the p-type region near the p–n interface begin to diffuse into the n-type region, leaving behind negatively charged ions in the p region and positive ions in the n region. These ion-charges build up until they suppress further movement of diffusing charges and raise a potential barrier. This potential is such that the positive charges reside in n region and negative charges reside in p region. Thus, the potential at p (side) is less than that at n(side).
Option B
Question 6
1 / -0

To get an output $$y = 1$$ from the circuit shown, the inputs $$A$$, $$B$$ and $$C$$ must be respectively

A
$$0, 1, 0$$

B
$$1, 0, 0$$

C
$$1, 0, 1$$

D
$$1, 1, 0$$

Solution

AND gate produces output as $$1$$ only when both of its inputs are $$1$$, and OR gate produces output as $$1$$ when either of its input is $$1$$.
Thus to get an output $$Y=1$$, input $$A$$ must be $$1$$, $$B$$ must be $$0$$ and $$C$$ must be $$1$$.
Question 7
1 / -0

When the inputs of a two input logic gate are $$0$$ and $$0$$, the output is $$1$$. When the inputs are $$1$$ and $$0$$ the output is $$0$$. The logic gate is the type

A
AND

B
NAND

C
NOR

D
OR

Solution

The output of AND gate is $$Y=A.B$$
Question 8
1 / -0

Which logic gate produces 'LOW' output when any of the inputs is 'HIGH'?

A
AND

B
OR

C
NAND

D
NOR

Solution
Question 9
1 / -0

Which of the following semi-conducting devices is used as voltage regulator?

A
Zener diode

B
LASER diode

C
Photo diode

D
Solar cell

Solution

Zener diode is used as a voltage regulator device because the voltage across the zener diode in reverse bias is constant after reaching certain value i.e. breakdown voltage.
Question 10
1 / -0

A logic gate whose output will be in logic $$0$$ state only when all inputs are in logic $$1$$ state is called.

A
AND

B
OR

C
NOR

D
NAND

Solution

NAND gate behaves the same as an AND gate with a NOT (inverter) gate connected to the output terminal