Digital Circuits Questions and Answers Part-18

1.What does ALVT mean?
a) All lower supply voltage while retaining TTL logic levels
b) ABT lower supply voltage while retaining TTL logic levels
c) Advanced version of LVT logic
d) All version of LVT logic

Answer: c
Explanation: ALVT stands for Advanced Low Voltage BiCMOS Technology (ALVT). It is a faster version of LVT family. It is an integration of less power dissipation and less noise of CMOS along with the high switching speed and output drive of BJT.

2. The full form of PTL is _____________
a) Pull transistor logic
b) Push transistor logic
c) Pass transistor logic
d) Post Transistor Logic

Answer: c
Explanation: The full form of PTL is “pass transistor logic”. It combines different logic families to design an integrated circuit. Thus, it reduces the number of transistors used by scraping off the unnecessary transistors.

3. CVSL means _____________
a) Complementary Voltage Switch Logic
b) Cascode Voltage Switch Logic
c) Complemented Voltage Switch Logic
d) Cascade Voltage Switch Logic

Answer: b
Explanation: Cascode Voltage Switch Logic (CVSL) refers to a CMOS-type logic family which is designed for certain advantages. It requires mainly N-channel MOSFET transistors to implement the logic using true and complementary input signals and also needs two P-channel transistors at the top to pull one of the outputs high

4. The basic building blocks of the arithmetic unit in digital computers are __________
a) Subtractors
b) Adders
c) Multiplexer
d) Comparator

Answer: b
Explanation: The basic building blocks of the arithmetic unit in digital computers are adders. Since a parallel adder is constructed with a number of full-adder circuits connected in cascade. By controlling the data inputs to the parallel adder, it is possible to obtain different types of arithmetic operations.

5. A digital system consists of _____ types of circuits.
a) 2
b) 3
c) 4
d) 5

Answer: a
Explanation: A digital system consists of two types of circuits and these are a combinational and sequential logic circuit. Combinational circuits are the ones which do not depend on previous inputs while Sequential circuits depend on past inputs.

6. In a combinational circuit, the output at any time depends only on the _______ at that time.
a) Voltage
b) Intermediate values
c) Input values
d) Clock pulses

Answer: c
Explanation: In a combinational circuit, the output at any time depends only on the input values at that time and not on past or intermediate values.

7. In a sequential circuit, the output at any time depends only on the input values at that time.
a) Past output values
b) Intermediate values
c) Both past output and present input
d) Present input values

Answer: c
Explanation: In a sequential circuit, the output at any time depends on the present input values as well as past output values. It also depends on clock pulses depending on whether it’s synchronous or asynchronous sequential circuits.

8. All logic operations can be obtained by means of __________
a) AND and NAND operations
b) OR and NOR operations
c) OR and NOT operations
d) NAND and NOR operations

Answer: d
Explanation: Since the logic gates NOR and NAND are known as universal logic gates, therefore it can be used to design all the three basic gates AND, OR and NOT. Thus, it means that any operations can be obtained by implementation of these gates.

9. The design of an ALU is based on __________
a) Sequential logic
b) Combinational logic
c) Multiplexing
d) De-Multiplexing

Answer: b
Explanation: The design of an ALU is based on combinational logic. Because the unit has a regular pattern, it can be broken into identical stages connected in cascade through carries.

10. If the two numbers are unsigned, the bit conditions of interest are the ______ carry and a possible _____ result.
a) Input, zero
b) Output, one
c) Input, one
d) Output, zero

Answer: d
Explanation: If the two numbers are unsigned, the bit conditions of interest are the output carry and a possible zero result.