VLSI Design UPDATED Exam Questions
and CORRECT Answers
How would you define VLSI or very large scale integration? - CORRECT ANSWER -
VLSI is essentially just a process that you use to create integrated circuits by incorporating
millions of MOS transistors onto a single chip. These ICs are necessary for engineering
integrated circuit microchips. You can then use the microchips for a wide variety of tools, like
telecommunication technologies and semiconductors
What is boolean logic and how do you use it? - CORRECT ANSWER - Boolean logic is
the foundation of Boolean algebra, which states that all values are either true or false. You can
use boolean logic in programs that make basic comparisons. It can help you make more informed
decisions based on whether a value is true or false.
How does a Boolean logic control the logical gates? - CORRECT ANSWER - The true
state in Boolean algebra is denoted by the number one, also known as logic one or logic high. On
the other hand, the false state is represented by the number zero, also known as logic zero or
logic low. In digital electronics, the presence of a voltage potential denotes a logic high.
Why do the present VLSI circuits use MOSFETs instead of BJTs? - CORRECT
ANSWER - The advantage of using MOSFETs over BJTs is that power dissipation and
leakage currents are minimized in the circuits, so they have been used instead. MOSFETS are
smaller (occupy tiny silicon area on IC chips), simpler in to manufacture, unipolar, don't need
current on their control pin (require more voltage)
What are the various regions of operation of MOSFET? How can we use these regions? -
CORRECT ANSWER - MOSFETs operate in three regions: the cut-off region, the triode
region, and the saturation region. The cut-off region and the triode region serve as switches. The
saturation region serves as an amplifier.
What do you understand by the threshold voltage? - CORRECT ANSWER - The minimum
voltage between the gate and source terminal that results in the formation of an inversion layer
connecting the source and drain is known as the threshold voltage of MOSFET. This voltage
defines the working of MOSFET. If the minimum voltage exceeds the threshold voltage, then
MOSFET will remain in the cut-off region.
, How can binary numbers give a signal or be converted into a digital signal? - CORRECT
ANSWER - The process of converting binary data, a sequence of bits, to a digital signal is
known as line coding. Line encoding can be polar, unipolar, or bipolar.
- CORRECT ANSWER - The key differences between TTL (Transistor-Transistor Logic)
and CMOS (Complementary Metal-Oxide-Semiconductor) chips lie in their power consumption
and switching speed. TTL chips consume more power but switch faster, making them suitable for
applications requiring high-speed operation. CMOS chips, on the other hand, have significantly
lower power consumption, making them ideal for battery-powered devices, but they may have
slightly slower switching speeds compared to TTL. CMOS is also more susceptible to static
discharge than TTL.
What does "the channel is pinched off" mean? - CORRECT ANSWER - Pinch-off occurs
when a voltage is applied to the drain (VD) until it reaches the drain voltage saturation (VDS).
This causes the depletion region at the drain to increase due to a decrease in the electrical field at
the drain edge, resulting in only a small electron, if any, being induced at the drain edge.
What is the most significant advantage of the CMOS chips over the TTL chips? - CORRECT
ANSWER - The main advantage of the CMOS chip over the TTL chip is that it has a
higher density of logic gates within the same material, which improves its efficiency. Another
significant advantage is that CMOS chips consume less power than TTL chips even when they
are idle.
What is Verilog and how does it differ from other standard programming languages? -
CORRECT ANSWER - Verilog is a type of hardware description language that describes
the electronic systems and circuits. You essentially prepare the circuit components inside of a
module that contains structural and behavioral statements. There are several reasons why it
differs from other normal programming languages. For starters, it has multiple threads and uses
simulation time concept, which the others don't. It also has basic circuit concepts, like primitive
gates. Whereas other programming languages, represent successive operations
In VLSI, what is the depletion region? - CORRECT ANSWER - When a positive voltage
is applied across the gate, the free holes (positive charge) repel from the area of the substrate
underneath the gate. These free holes leave a carrier-depletion region behind when they are
pushed down the channel region of the gate's surface.
and CORRECT Answers
How would you define VLSI or very large scale integration? - CORRECT ANSWER -
VLSI is essentially just a process that you use to create integrated circuits by incorporating
millions of MOS transistors onto a single chip. These ICs are necessary for engineering
integrated circuit microchips. You can then use the microchips for a wide variety of tools, like
telecommunication technologies and semiconductors
What is boolean logic and how do you use it? - CORRECT ANSWER - Boolean logic is
the foundation of Boolean algebra, which states that all values are either true or false. You can
use boolean logic in programs that make basic comparisons. It can help you make more informed
decisions based on whether a value is true or false.
How does a Boolean logic control the logical gates? - CORRECT ANSWER - The true
state in Boolean algebra is denoted by the number one, also known as logic one or logic high. On
the other hand, the false state is represented by the number zero, also known as logic zero or
logic low. In digital electronics, the presence of a voltage potential denotes a logic high.
Why do the present VLSI circuits use MOSFETs instead of BJTs? - CORRECT
ANSWER - The advantage of using MOSFETs over BJTs is that power dissipation and
leakage currents are minimized in the circuits, so they have been used instead. MOSFETS are
smaller (occupy tiny silicon area on IC chips), simpler in to manufacture, unipolar, don't need
current on their control pin (require more voltage)
What are the various regions of operation of MOSFET? How can we use these regions? -
CORRECT ANSWER - MOSFETs operate in three regions: the cut-off region, the triode
region, and the saturation region. The cut-off region and the triode region serve as switches. The
saturation region serves as an amplifier.
What do you understand by the threshold voltage? - CORRECT ANSWER - The minimum
voltage between the gate and source terminal that results in the formation of an inversion layer
connecting the source and drain is known as the threshold voltage of MOSFET. This voltage
defines the working of MOSFET. If the minimum voltage exceeds the threshold voltage, then
MOSFET will remain in the cut-off region.
, How can binary numbers give a signal or be converted into a digital signal? - CORRECT
ANSWER - The process of converting binary data, a sequence of bits, to a digital signal is
known as line coding. Line encoding can be polar, unipolar, or bipolar.
- CORRECT ANSWER - The key differences between TTL (Transistor-Transistor Logic)
and CMOS (Complementary Metal-Oxide-Semiconductor) chips lie in their power consumption
and switching speed. TTL chips consume more power but switch faster, making them suitable for
applications requiring high-speed operation. CMOS chips, on the other hand, have significantly
lower power consumption, making them ideal for battery-powered devices, but they may have
slightly slower switching speeds compared to TTL. CMOS is also more susceptible to static
discharge than TTL.
What does "the channel is pinched off" mean? - CORRECT ANSWER - Pinch-off occurs
when a voltage is applied to the drain (VD) until it reaches the drain voltage saturation (VDS).
This causes the depletion region at the drain to increase due to a decrease in the electrical field at
the drain edge, resulting in only a small electron, if any, being induced at the drain edge.
What is the most significant advantage of the CMOS chips over the TTL chips? - CORRECT
ANSWER - The main advantage of the CMOS chip over the TTL chip is that it has a
higher density of logic gates within the same material, which improves its efficiency. Another
significant advantage is that CMOS chips consume less power than TTL chips even when they
are idle.
What is Verilog and how does it differ from other standard programming languages? -
CORRECT ANSWER - Verilog is a type of hardware description language that describes
the electronic systems and circuits. You essentially prepare the circuit components inside of a
module that contains structural and behavioral statements. There are several reasons why it
differs from other normal programming languages. For starters, it has multiple threads and uses
simulation time concept, which the others don't. It also has basic circuit concepts, like primitive
gates. Whereas other programming languages, represent successive operations
In VLSI, what is the depletion region? - CORRECT ANSWER - When a positive voltage
is applied across the gate, the free holes (positive charge) repel from the area of the substrate
underneath the gate. These free holes leave a carrier-depletion region behind when they are
pushed down the channel region of the gate's surface.
