Hello everyone.
I'm Typhoon and welcome to this lecture.
In this lecture, we will dive deep into one of the most fundamental and powerful innovations in digital
electronics, which is C.
Or you may ask what this means is CMOs stands for complementary metal oxide semiconductor.
This elegant design principle lies at the heart of almost every modern logic circuit, from your computer's
CPU to the microcontroller inside a smartwatch.
This is a more smarter way to switch, and in earlier digital logic designs, we relied on resistors
for pull up and pull down operations.
While this worked, it has significant limitations.
As learned and then explained in our previous lectures, it consumed continuous power even when the
signal wasn't switching, and it was relatively slow due to the passive nature of resistors.
And this is where the cosmos comes in as a game changer.
The CMOs technology.
Complementary metal oxide semiconductor circuits use two complementary types of transistors a p-channel
mOSFET, also called PMOs, which conducts when the input is low, and an n-channel mOSFET or an M or
S, which conducts when the input is high.
You have learned P-channel and n-channel mOSFET in previous lectures, so I.
If you didn't watch the previous lecture, I highly, highly recommend you watch this course's lectures
one by one.
And do not skip any lectures between lectures here.
And yeah, you need to learn about mOSFET and p-channel MOSFETs and n-channel mOSFET in order to understand
this CMOs concept at all.
So by pairing this together and connecting their drains like that, you can see we have connected their
drains.
We form basically a CMOs inverter.
This simple yet powerful arrangement is the building block for countless digital circuits.
So here in this, uh, here I have created a CMOs inverter.
Um, now at the top of the circuit we see a p-channel mOSFET.
It is it's actually use a different color.
So yeah, at the bottom of the circuit, uh, we are seeing the p-channel mOSFET.
Its source terminal is connected to five volts, which we treat this logic one or binary one, logic
II or binary one.
91.
And at the bottom here we see an n channel mOSFET.
And now its source is connected to zero volts representing the logic low or binary zero.
And we also have the gate terminals of both transistors are tied together like this and used as the
input to the inverter and the drain terminals of the.
Both MOSFETs are also connected together, forming the output of the inverter.
Now this symmetrical design allows one transistor to be on while the other is off depending the input
voltage.
Now, this mutual exclusivity is what makes CMOs so power efficient and responsive.
So let's now examine how the circuit behaves under different input conditions Which shows two cases
here.
In the case, one input voltage of the input voltage is five volts.
The input gate is at five volts.
Now this turns off the P-channel mOSFET because p MOSFETs require low voltage low voltage to conduct
here, and the N-channel mOSFET turns on here.
Now the output is connected to zero volts through the n mOSFET, so n channel turns on because it is
activated by a high voltage.
So the output is pulled.
Now is low so it is zero volts.
And in the case two, if the input gate here is zero volts, what we will get basically is the p-channel
mOSFET turns on, and now a low gate voltage allows it to conduct, and the n-channel mOSFET turns off
as it needs high voltage to conduct.
This makes sense, right?
So with the p-channel conducting, the output is connected.
To what.
Where to five volts.
So basically the output is pulled high.
Let me fix my microphone here.
Yeah.
So the output is pulled high which is basically five volts in our this diagram.
And yeah now if we summarize this logic with the table what we will get basically is we have the gates.
As you know the gates is basically the input of our transistors.
And we also have the output or drains.
That's actually first drains which is output.
So here in the input, if we give the zero volts which is low in the output we will get five volts.
If we give five volts we will get zero volts.
So the output is basically always opposite of the input like a logic node.
And we can also use the CMOs and gate using inverters.
Now let's move beyond inverter and analyze the CMOs and and gate.
Um so here in this diagram I'm basically uh demonstrating how we can construct an and gate using three
CMOs logic stages.