I am new to implementing boolean expressions in CMOS form, and I understand that the "C" in CMOS stands for "Complementary", so it is an inverter circuit.
What I don't understand is: All the tutorials say that if you want to design an "AND" gate you have to place the transistors in series if they are nMOS and in parallel if they are pMOS. Why is that?
Why can't we just say "for AND gate: place the nMOS in parallel and the pMOS in series" so that we'll be able to implement the functions directly, without need of an inverter before the output?
Would that create some problem that I haven't come across yet?
I had a CMOS full adder circuit that I had to extract the boolean expression from, and I noticed that the expression I was extracting was correct according to the aforementioned implementation rules, but then I noticed the inverter before the output, and got confused. Is there some logical reason for the rules being like this?
EDIT: In below picture, the OR operation in nMOS corresponds to placing the transistors in parallel. The opposite is true for pMOS. My question is, why did we have to implement the inverse function? Couldn't we have made the circuit directly, using the original function and inverting the "rules" about OR corresponding to nMOS in parallel (making them "nMOS corresponds to nMOS in series" instead)?
(link of video where i got the above screenshot:https://www.youtube.com/watch?v=7XEUB_dTaK0)