Question

What are the advantages and disadvantages of the NMOS?

Answer 1

NMOS is a N-type metal-oxide-semiconductor logic uses n-type field-effect transistors to implement logic gates. It is a type of semiconductor that charges negatively.

Advantages of NMOS

• The Major Advantage of NMOS circuits are its high speed (especially, in large-fan-in NOR gates) and low transistor count.

• NMOS has uniform structure and easy to manufacture compared to CMOS.

• N-channel ICs can be smaller for the same complexity .They can be more complex with no increase in silicon area.

• On the negative side of NMOS is the static power consumption of the pull-up transistor as well as the reduced output voltage swing and gain, which makes the gate more susceptible to noise.

• By using NMOS, the overall speed improvement can be substantial at the cost.

• pseudo-NMOS supports a power-down mode at no extra cost.

Disadvantages of NMOS

• The Major Disadvantage of NMOS is that a DC current must flow through a logic gate even when the output is in a steady state.

• High static power dissipation, (power drain even when the circuit is not switching.)

• Velocity saturations

• Latch up problems

• When using NMOS only, logic '1' (i.e Vdd) suffers a thresold drop. Output will be Vdd – threshold Voltage.

• Difficult to make an NMOS n-channel device that is off at zero gate voltage compared to PMOS