VLSI DESIGN TEST QUESTIONS AND
ANSWERS
How would you describe the VLSI or very large-scale integration? - ANSWER
VLSI, in simple words, is merely a process that you are using to build integrated
circuits by integrating millions of MOS transistors onto a single chip. These ICs
form a vital part of the engineering of integrated circuit microchips. After
constructing microchips, you will be able to use them in different types of tools,
such as in telecommunication technologies and semiconductors.
What is boolean logic, and how do you use it? - ANSWER Boolean logic is
the basis of Boolean algebra, stating 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 Boolean logic control logical gates? - ANSWER The true state in
Boolean algebra is represented by the number one and it is called as logic one or
logic high. On the other hand, false state in Boolean algebra is represented by
the number zero and is referred to as a logic zero or logic low. In digital
electronics, the existence of a voltage potential marks a logic high.
Why do the present VLSI circuits use MOSFETs instead of BJTs? - 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 different regions of operation of MOSFET? How can we use these
regions? - ANSWER The different regions of operation of MOSFET are cut-
, off region, triode region and saturation region. The cut-off region and the triode
region act like switches. The saturation region acts like an amplifier.
What do you understand by the threshold voltage? - ANSWER The threshold
voltage of MOSFET is the minimum voltage between the gate and source
terminal, which gives rise to the formation of an inversion layer that connects
the source and drain. 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 are these binary numbers going to signal, or be converted, to a digital
signal? -
ANSWER
Line coding is the process of converting binary data, a collection of bits, to a
digital signal. Line encoding can be polar, unipolar, or bipolar.
-
ANSWER
TTL (Transistor-Transistor Logic) and CMOS (Complementary Metal-Oxide-
Semiconductor) chips differ based on power consumption and their relative
switching speed. TTL chips use more power but switch faster; thus, they are
appropriate for applications requiring very high operating speed. The CMOS
chips have much lower power consumption and, therefore, are suitable for
battery operation, but the switching speed is somewhat lower compared to that
of TTL chips. It is also more susceptible to static discharge compared to TTL.
What is meant by "the channel is pinched off"? - ANSWER Pinch-off is when
a voltage is applied to the drain, VD, until it reaches the drain voltage
saturation, VDS. The depletion region at the drain increases due to a reduction
in the electrical field at the drain edge, which in turn induces only a small
electron, if any, at the drain edge.
ANSWERS
How would you describe the VLSI or very large-scale integration? - ANSWER
VLSI, in simple words, is merely a process that you are using to build integrated
circuits by integrating millions of MOS transistors onto a single chip. These ICs
form a vital part of the engineering of integrated circuit microchips. After
constructing microchips, you will be able to use them in different types of tools,
such as in telecommunication technologies and semiconductors.
What is boolean logic, and how do you use it? - ANSWER Boolean logic is
the basis of Boolean algebra, stating 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 Boolean logic control logical gates? - ANSWER The true state in
Boolean algebra is represented by the number one and it is called as logic one or
logic high. On the other hand, false state in Boolean algebra is represented by
the number zero and is referred to as a logic zero or logic low. In digital
electronics, the existence of a voltage potential marks a logic high.
Why do the present VLSI circuits use MOSFETs instead of BJTs? - 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 different regions of operation of MOSFET? How can we use these
regions? - ANSWER The different regions of operation of MOSFET are cut-
, off region, triode region and saturation region. The cut-off region and the triode
region act like switches. The saturation region acts like an amplifier.
What do you understand by the threshold voltage? - ANSWER The threshold
voltage of MOSFET is the minimum voltage between the gate and source
terminal, which gives rise to the formation of an inversion layer that connects
the source and drain. 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 are these binary numbers going to signal, or be converted, to a digital
signal? -
ANSWER
Line coding is the process of converting binary data, a collection of bits, to a
digital signal. Line encoding can be polar, unipolar, or bipolar.
-
ANSWER
TTL (Transistor-Transistor Logic) and CMOS (Complementary Metal-Oxide-
Semiconductor) chips differ based on power consumption and their relative
switching speed. TTL chips use more power but switch faster; thus, they are
appropriate for applications requiring very high operating speed. The CMOS
chips have much lower power consumption and, therefore, are suitable for
battery operation, but the switching speed is somewhat lower compared to that
of TTL chips. It is also more susceptible to static discharge compared to TTL.
What is meant by "the channel is pinched off"? - ANSWER Pinch-off is when
a voltage is applied to the drain, VD, until it reaches the drain voltage
saturation, VDS. The depletion region at the drain increases due to a reduction
in the electrical field at the drain edge, which in turn induces only a small
electron, if any, at the drain edge.
