Semiconductor Electronics: Materials, Devices and Simple Circuits Test 20

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Semiconductor Electronics: Materials, Devices and Simple Circuits Test 20

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Question 1
1 / -0

The logic symbols shown here are logically equivalent to :-

A
$$AND$$ and $$OR$$ gate

B
$$NOR$$ and $$NAND$$ gate

C
$$OR$$ and $$AND$$ gate

D
$$NAND$$ and $$NOR$$ gate

Solution
Question 2
1 / -0

Conventional flow of current will always be from -

A
p type$$\rightarrow$$n type

B
n type $$\rightarrow$$p type

C
n Type $$\rightarrow$$ n type

D
None of these

Solution

The holes in the covalent bonds of p-type semiconductor. They appear to move towards n-type semiconductor. Because the electrons in the covalent bonds of n-type semiconductor (not free electrons) jump towards p-type semiconductor due to plenty of holes available in the covalent bonds at p-side.

Hence, conventional current flow from p-type to n-type.
Question 3
1 / -0

The process by which ac is converted into dc is known as

A
Purification

B
Amplification

C
Rectification

D
Current Amplification

Solution

The process by which ac is converted into dc is known as " Rectification".
Question 4
1 / -0

Semi-conductor are formed if the bonds are

A
van der Walls

B
ionic

C
metallic

D
covalent

Solution
Question 5
1 / -0

The nature of binding for a crystal with alternate and evenly spaced positive and negative ions is:

A
metallic

B
covalent

C
dipolar

D
ionic

Solution
Question 6
1 / -0

A diode made of silicon has a barrier potential of $$0.7\ V$$ and a current of $$20\ mA$$ passes through the diode when a battery of emf $$3\ V$$ and a resistor is connected to it. The power dissipated across the resistor and diode are

A
$$0.046\ W, \ 0.014\ W$$

B
$$4.6\ W,\ 0.14\ W$$

C
$$0.46\ W,\ 0.14\ W$$

D
$$46\ W, \ 14\ W$$

Solution

Given that:
$$V_D = 0.7\ V$$
$$I = 20\ mA = 0.02\ A$$
$$V_B = 3\ V$$

Now, $$P = (V_B - V_D){I}$$
or $$P=(3-0.7)0.02=0.046\ W$$

And power across $$R_D$$ is
$$P_{R_D} = (V_D)I$$
$$P_{R_D} = 0.7\times 0.02 = 0.014\ W$$
Question 7
1 / -0

AND gate

A
it has no equivalence to switching circuit.

B
it is equivalent to series switching circuit.

C
it is equivalent to parallel switching circuit.

D
it is a mixture of series and parallel switching circuit.

Solution

AND gate is only active when both the inputs are high same as series switching circuit which is active only when both switches are closed.
Question 8
1 / -0

In an insulator, the energy gap between conduction band and valence band is about

A
$$0\ eV$$

B
$$6\ eV$$

C
$$1\ eV$$

D
$$0.6\ eV$$

Solution

Atoms are neutral in the insulator, thus there are no valence electrons in the outer orbit. The electrons are tightly bound with the nucleus hence, at room temperature thermal energy is not enough to push the electrons into conduction band and hence, no electrons are available for conduction. The energy required for electron to escape out from orbit and to over come the energy gap is thus of the order of $$6\ eV$$.
Question 9
1 / -0

Consider the following statements A and B and identify the correct answer:
A) germanium is preferred over silicon in the construction of Zener diode.
B) germanium has high thermal stability than silicon in the construction of Zener diode.

A
Both (A) and (B) are true.

B
Both (A) and (B) are false.

C
(A) is true but (B) is false.

D
(A) is false but (B) is true.

Solution

Germanium diode does not have a sharp breakdown in reverse bias and hence, the voltage does not remain constant at $$5\ V$$ after breakdown while silicon diode is better in this respect. Hence, silicon is preferred in Zener diode. Also, thermal stability of silicon is better than germanium.
Question 10
1 / -0

Digital circuit can be made by repetitive use of :

A
OR gates

B
AND gates

C
NOT gates

D
NAND gates

Solution

NAND gate is called universal gate because all other logic gates such as AND, OR and NOT can be constructed from various combinations of NAND gates. Thus, any digital circuit can be made by appropriate repetitive use of NAND gate.