AND gate transistor sizing

Thread Starter

vead

Joined Nov 24, 2011
629
AND gate with cmos transistor
we can create cmos AND gate with 3 nmos and 3 pmos transistor

Equation X=AB

AND gate cmos circuit= <-NAND--Inverter->

I want to size the transistor so that the output resistance is same as that of inverter with nmos W/L=3/2 and pmos W/L=6/2

inverter with nmos W/L=3/2 and pmos W/L=6/2

parallel pmos (L will double with same W)

pmos 1 W/L=6/4 and pmos 2 W/L = 6/4

nmos series ( W will double with same L)

nmos 1 W/L= 3/4 and nmos 2 W/L=3/4
transistor size for AND gate cmos

nmos 1 W/L=6/4
nmos 2 W/L=6/4
nmos 3 W/L=3/2


pmos 1 W/L=3/4
pmos 2 W/L=3/4
pmos 3 W/L=3/2

IS this correct sizing for AND gate
 
Last edited:

Thread Starter

vead

Joined Nov 24, 2011
629
look at this Image

given, Q5 nmos W/L=3/2
Q6 pmos 3 W/L=3/1

I want to determine size Q1,Q2,Q3 ,Q4a

I made following
Q1 nmos W/L=6/4
Q2 nmos W/L=6/4
Q3 pmos 1 W/L=3/4
Q4 pmos 2 W/L=3/4
 

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Thread Starter

vead

Joined Nov 24, 2011
629
how to size transistors for AND gate

look at Image that I have uploaded

AND gate create with NAND gate INVERTER
there are six transistor used to create AND gate
two nmos connected in series before the Inverter
two pmos connected in parallel in NAND gate (before inverter)

sizing ratio for nmos W/L=3/2 and pmos W/L =6/2 in inverter circuit

how to size for all transistor ?
 

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Thread Starter

vead

Joined Nov 24, 2011
629
look at this sizing
Nmos W/L=3/2 and Pmos W/L=6/4( transistor in inverter circuit)

caseI - when to mosfet in series this is similar to one transistor with double length and same width
Example two series nmos with W=1 and L=1
resultant W/L=1/2

case II when to mosfet in parallel W will be double with same L
Example- two pmos in parallel with w=1 and L=1
resultant W/L=2/1

So I made following sizing for AND gate circuit
nmos W/L=3/2 and pmos W/L=6/4 (inverter circuit)
nmos W/L=3/1 and pmos W/L=3/4 (for nand gate circuit)
 

WBahn

Joined Mar 31, 2012
26,398
You stated in the original post: "I want to size the transistor so that the output resistance is same as that of inverter with nmos W/L=3/2 and pmos W/L=6/2"

Will: "nmos W/L=3/2 and pmos W/L=6/4 (inverter circuit)" accomplish that?
 
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