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NAND or NOR is faster

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is pmos slower compared to nmos, bcos nand has 2 nmos and nor has two pmos and all say that nand is faster than nmos?
 

incisive said:
is pmos slower compared to nmos, bcos nand has 2 nmos and nor has two pmos and all say that nand is faster than nmos?
Click to expand...

excuse me but...i can't understand anything from what you have said:)
 

He said, that it doesn't depend what kind of logic function is it. It depends on the technology used to construct it.
 

aha...now i got it
there were some terms he messed up though
that's why i just needed more clarification
that's all:)
and ... already the whole conversation was talking about the mos implementation of the gates :)
 

to decide fastness, we hav to consider the logic family that is involved int he manufacturing those gates and technology like nmos or pmos.
however ecl family basic gate is nanad. so we can say nand is faster.
 

Hi,
PMOS are slower than NMOS.
In NAND the PMOS are in parallel in pull up circuit.
In NOR the PMOS are in series in pull up circuit.

Hence rise time of NAND is higher than NOR.
However the fall time of NOR gate is higher than NAND

thanks
sarfraz
 

another question: nand and nor , which one has less area?
 

Hi,
Which will take more area depends on the design.
Whether you want rise time equal to fall time or some other similar requirement, then the area required will change.

thanks
sarfraz
 

The PMOS are slower than NMOS.
In NAND the PMOS are in parallel in pull up circuit.
In NOR the PMOS are in series in pull up circuit.

So, NAND is faster.
 

Hi
THis book helps u for Logical Effort in VLSI design
 

yes it right NAND is faster

Added after 53 minutes:

AND THANX FOR LOGICAL EFFORT: BOOK
 

depends on usage
NOR is faster for random access
NAND is faster for sequence access
 

Depends on logic you are using :
For example in static CMOS logic a nand will be faster
whereas in pseudo logic a nor will be faster

tronix
 

p_shinde said:
Pmos is slower than NMOS becos of high electron velocity, in Nand for I/P to O/P we need to pass only one of the PMOS xsistor while in case of NMOS xsistor we have to go through both PMOS xsistor,


thats why Nand is faster than NOR...


Bye,
Prasad
Click to expand...


this is one good logical answer and very easy to understand.

Added after 1 minutes:

tronix said:
Depends on logic you are using :
For example in static CMOS logic a nand will be faster
whereas in pseudo logic a nor will be faster

tronix
Click to expand...

can u explain further why is it so?
 

Hi,
Pseudo logic NOR gates are faster because PSUEDO LOgic NOR gates have high Fan in Capabitlity.

Thanks
Shaikh Sarfraz
 

hustyw said:
another question: nand and nor , which one has less area?
Click to expand...

Nand has less area in the flash memory design.
 

when we analyze transistor level diagram for nand and nor, pmos trnasistor are in pararllel in the case nand, series in the case of nor for charging and discharging will be fast in the case for nand when u compare with nor.
 

Area wise nand will be less as u don't require big pmoses there .
 

With the same area, NAND is faster than NOR.
 

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