1. Explain the slope of the clock?
Ans. It is the difference in time between the arrival of Clock edge active to different flipflops of the same chip
2. Why do you prefer the NAND gate over NOR gate for its manufacture?
Ans. NAND is a better gate for design than NOR because in the
Level of the transistor electron mobility is usually three
Times the holes compared to NOR and therefore the NAND is a
Faster door Additionally, the door-leak in NAND structures
It is much smaller.
3. What is body effect?
Ans. In general, multiple MOS devices are made on a common substrate. As a result, the substrate
The voltage of all devices is normal. However, when connecting the devices in series,
It can result in an increase in the source-to-substrate voltage while proceeding vertically along the
Chain series (Vsb1 = 0, Vsb2 0). Which results Vth2> Vth1.
4. Why is the substrate in NMOS connected to ground and in PMOS to VDD?
Ans. We try to reverse bias not the channel and the substrate, but we try to maintain the
Drainage, the source joints are inversely polarized with respect to the substrate so that we do not lose our
Current in the substrate.
5. What is the fundamental difference between a MOSFET and BJT?
Ans. In MOSFET, the current flow is due to electrons (n-channel MOS) or holes (p-
MOS channel) - In BJT, we see current due to the two carriers .. electrons and holes. BJT is a
Current control device and MOSFET is a voltage controlled device
In CMOS technology, in digital design, why do we design the size of PMOS to be higher
Let nmos.What determines the size of pmos wrt nmos. Although this is a simple
6. Question try to list all possible reasons?
Ans. a)In PMOS the carriers are holes whose mobility is smaller than that of the electrons,
b)Bearers in NMOS. That means that PMOS is slower than an NMOS. In CMOS technology, nmos
c)Helps to lower the output to the ground ann PMOS helps pull the output to Vdd.
d)If the sizes of PMOS and NMOS are the same, PMOS takes a long time to load
e)Output node. If we have a larger PMOS there will be more carriers to load the node
f)Quickly and overcome the slow nature of PMOS. Basically, we do all this to get an equal increase
g) And the drop times for the output node.
7. Why do PMOS and NMOS have the same size in transmission doors?
Ans. At the Transmission Gate, PMOS and NMOS are helping each other instead of competing with each other.
That is the reason why we do not need to size them as in CMOS. In the CMOS design we have
Competing NMOS and PMOS, which is why we try to scale them proportionally to their
mobility.