nor gate cmos circuit

[vead]

hello
I made Nor gate with coms transistor
please check the connection

If my diagram is correct then I want to decide length and width of transistor ?
still I have not decide width and length I just want to confirm that my diagram is correct ?

 

[Harald Kapp]

The source of the PMOS transistors is incorrectly tied to the output. It should go to Vdd.

If you want a more or less symmectrival output you have to take into account that a PMOS has 1/2 the conductivity of an NMOS for the same W/L ratio. Since for a high output you have 2 PMOS in series, you have 1/4 the conductivity of a single NMOS in the pull-down leg of the output (for equal W/L). For a symmetrical output you therefore have to design W/L(PMOS)=4*W/L(NMOS).
The absolute value of W and L depends mainly upon the available technology and max. output current.

 

[vead]

The source of the PMOS transistors is incorrectly tied to the output. It should go to Vdd.

If you want a more or less symmectrival output you have to take into account that a PMOS has 1/2 the conductivity of an NMOS for the same W/L ratio. Since for a high output you have 2 PMOS in series, you have 1/4 the conductivity of a single NMOS in the pull-down leg of the output (for equal W/L). For a symmetrical output you therefore have to design W/L(PMOS)=4*W/L(NMOS).
The absolute value of W and L depends mainly upon the available technology and max. output current.

If pmos =6/1 then nmos will be 3/1
according to your formula W/L(PMOS)=4*W/L(NMOS).

pmos = 6/1 and nmos = 6/2 *4=12/1

circuit is here

 

[Harald Kapp]

pmos = 6/1 and nmos = 6/2 *4=12/1

No.
W/L(PMOS)=4*W/L(NMOS)
Therefore if W/L(PMOS)=6/1, then W/L(NMOS)=6/1 *1/4= 6/4=/3/2

The PMOS needs to be wider than the NMOS for the same conductivity and channel length.

 

[vead]

No.
W/L(PMOS)=4*W/L(NMOS)
Therefore if W/L(PMOS)=6/1, then W/L(NMOS)=6/1 *1/4= 6/4/3/2

The PMOS needs to be wider than the NMOS for the same conductivity and channel length.

ok thank you very much

some specification for cmos nor gate
.*dc supply voltage
* dc input voltage
*dc output voltage
*dc input current
*dc output current
* power dissipation

ok If we have two known value then we can determine another value
example If we know voltage and resistance then we can determine current by ohms law

can you give me some homework ?
can you give me some numeric value to determine unknown value like I mention in above spcification actually I want to learn by doing some real work, that circuit is mine i want to play with this circuit I will do some home work so please guide me

 

[Harald Kapp]

Sorry, I've been out of the IC design business for years. Luckily so far your questions were rather basic and I was able to answer them off the cuff. I do not have any material at hand that might be suitable for homework or for more detailed design of your circuit (besides, you'd neeed the parameters of the underlying manufacturing technology).
I'm pretty sure that if you search the internet, you will find suitable assignments. It seems that especially US American universities often make their material public.

 

[vead]

ok thanks lot I have question
I made that circuit on proteus software
can I use proteus to simulate that circuit ?

 

[Harald Kapp]

I don't know, because I don't know proteus. If you have suitable models for the transistors it may work. Just try it.