CMOS Resistance: Drawing NAND & Solutions

[nobrainer612]

Homework Statement

I drew a NAND in the picture.

The Attempt at a Solution

I know when A and B are both high ( value 1), resistance will be Rn + Rn because those 2 NMOS will be turned on and resistance will added up since they are in series.

Also when A and B are both low ( value 0), both PMOS will be turned on. My first question is, 1.) is the resistance become Rp*Rp/(Rp + Rp) because they are in parallel?

My second question is, if A is high (value 1) and B is low ( value 0) , output should be VDD ( value 1). But what will be resistance be? I think they are neither in series nor parallel. So will the resistance only become Rp ?

Hope somebody can share their ideas. Thank you

 

[NascentOxygen]

I know when A and B are both high ( value 1), resistance will be Rn + Rn because those 2 NMOS will be turned on and resistance will added up since they are in series.

Also when A and B are both low ( value 0), both PMOS will be turned on. My first question is, 1.) is the resistance become Rp*Rp/(Rp + Rp) because they are in parallel?

My second question is, if A is high (value 1) and B is low ( value 0) , output should be VDD ( value 1). But what will be resistance be? I think they are neither in series nor parallel. So will the resistance only become Rp ?

Hope somebody can share their ideas. Thank you

Hi nobrainer612! Those would be my answers, too.

Can you simplify this expression: Rp*Rp/(Rp + Rp)

 

[nobrainer612]

sorry but I don't get what you mean.

Can you tell me if those I assumed are correct? because I am interested what the resistance is .

simplify this expression: Rp*Rp/(Rp + Rp) : isn't that equal (Rp^2) / 2*Rp = Rp/2?


So what I assumed:

if A is high (value 1) and B is low ( value 0) -----> resistance = Rp only?
Also when A and B are both low ( value 0) -----> resistance = Rp/2 ? :shy:

 

[NascentOxygen]

if A is high (value 1) and B is low ( value 0) -----> resistance = Rp only? ✔
Also when A and B are both low ( value 0) -----> resistance = Rp/2? ✔

 

[DeeNos]

I appreciate your attempt at drawing the NAND and your understanding of the resistance values when A and B are both high or low. To answer your first question, yes, when both PMOS are turned on, the resistance will become Rp*Rp/(Rp + Rp) since they are in parallel.

For your second question, the resistance will indeed only become Rp when A is high and B is low, as they are not in series or parallel. This is because the PMOS on the bottom will be turned off, so the only resistance in the circuit will be from the top PMOS.

I would also like to add that in CMOS circuits, the resistance values are not constant and can vary depending on the input voltage and other parameters. It would be helpful to consider these factors in your analysis. Overall, your understanding of the resistance values in a NAND circuit is correct and I encourage you to continue exploring and learning more about CMOS circuits.