1.
DO NOT state true of false without explations. If you do, I will report you as SPAM. Please
answer with details.
For each of the following statements. state "T" for true or "F"' for false.
(1) A CMOS inverter is driving a load capacitor, if the W/L of CMOS (including both NMOS
and PMOS) doubles, the propagation delay will be reduced to half of its original value.
(2) In standard CMOS logic circuits, NAND circuits are preferred than NOR circuits because
NAND circuits have a smaller area than NOR circuits under the constraint of the same
propagation delay.
(3) in the pseudo-NMOS logic circuits, NAND circuits are preferred than NOR circuits because
NAND circuits have a smaller area than NOR circuits under the constraint of the same
propagation delay.
(4) For a NMOS pass gate transistor, the highest output voltage is less than VDD, the lowest
output voltage is equal to 0.
Solution
(1)TRUE
delay in cmos circuit with cpacitive load is inveresly propotional to drain current of mosfet and
drain current of mosfet is directly propotional to W/L ratio so delay in cmos circuit is inversely
propotional to W/L ratio.
Hence as W/l ratio is doubles the delay in CMOS circuit is halved
(2)TRUE
we prefer sop implementation only because it requires nand gate. in the nand gate two pmos are
in parallel while in the nor gate the two pmos are in series. so the latter case leads to delays
because of the low mobility of the holes. and to match the speed of operation of pmos with the
nmos the size of the pmos has to be increased. this requires more silicon area which again leads
to more cost.
(3)False

2.
When designing pseudo-NMOS logic gates we can consider that the NOR pseudo-NMOS logic
gate compared to NAND pseudo-NMOS logic gate.These advantages occur beacuse the only
NMOS gates we use are connected in parallel for NOR gate whereas the only NMOS gate are
connected in series for NAND gate due to which NAND has more propogation delay than NOR
gate for psuedo nmos logic circuit
(4)TRUE
Output of high of nmos pass transistor will be VDD-Vt.Where Vt is the threshold voltage.here
Vt is the voltage used up is settting channel in NMOS transistor.But for logic low out[ut no
current is needed to flow in nmos hence no extra voltage drops.So logic low output of NMOS is
0.