When designing hardware, especially for portable gadgets or embedded systems.
One of the biggest concerns is power efficiency.
But why?
Because if a device is powered by a battery, it needs to use as little energy as possible to last longer,
stay cooler, and work reliably without failure.
So basically, in circuits, heat equals inefficiency, and power consumption in a circuit isn't random.
It follows the behavior of three key electromagnetic properties.
The one is resistance.
Capacitance and inductance.
And among this, resistance plays the major role in consuming the electrical energy and turning it Into
heat, which is essentially wasted energy.
Now let's first understand how.
Two important terms that form the foundation of this topic.
The first is energy.
Energy is basically the ability to do work.
Now in electrical systems it is measured in joules.
And the power is the rate at which energy is consumed or transformed.
It is measured in watts or uppercase W, where basically the one watt equals to one joule per second.
So one joule second.
Now think of it this way if energy is how much work you can do.
The power is how fast you do it.
Now let's understand the stored energy in batteries.
So imagine you have a backup battery and labeled as 240 watt hour.
So what does this mean practically?
So it basically means it can deliver 240W of power steadily for one hours.
So if we want to convert watt hours into joules, which we need to do that to understand the total energy
stored, we multiply by the number of seconds in an hour.
So basically 240 watt hours multiplied by 3600 seconds Hours and it will be basically equal to
864,000
joules.
Now this means the battery stores 864,000 joules of energy.
And to put it another way, that's basically enough to power a 60 watt device continuously for 4 hours
or 120 watt device for two hours, or 240 watt device for one hours, or 480 watt device for 30 minutes.
That's basically how the battery labeling works in electronics.
We calculate power using a simple but powerful formula.
P equals v and I.
This is power.
Remember power is watts, V is voltage.
Basically is V and I is current through the component in amperes.
Now this tells us exactly how much electrical energy is being used at any moment.
Now, because of the official definitions of voltage and current.
This is also defines what a what actually is.
So one watt equals one volt.
Multiply by one amperes.
In other words, one that is one volt times one ampere.
So in a circuit, if we have ten amps or let's actually use our phone charger, right.
If your phone charger is ten watts delivers ten watts of power, it will be basically probably five
volts multiplied by two amperes.
Now go and read your chargers.
Rates.
So here I have 33W of charger.
It also charge 15W.
So it is written here that 15W is basically five volts multiplied by three ampere so it delivers five
volts at three amperes current.
So if I, if I and I have 33W some shame phone charger I have here, it says 33W which is fast charging
and it delivers 33W.
Fast output is 11V and three amperes.
Yeah.
It delivers 33W using 11V, volts and three amperes.
Now go and read the power efficiency of other electronic components.
It is interesting.
Believe me.
Now we have learned about this.
Yeah.
And you also learned about the passive components in our previous lectures, including capacitors,
inductors.
You will also learn about the resistors here as well, which is an important component.
Also important topic to understand how CPUs central processing units work.
Yeah.
Now let's break down each type of passive component behaves with respect to energy use.
So basically the capacitors.
When charging, a capacitor lets the current flow temporarily and once fully charged, it blocks DC
current completely.
And at that point it consumes almost almost no power.
But not zero power because not component.
No, there's no component that is 100% power efficient.
And it also stores energy in an electric field between its place and for the inductors or inductance,
we have what an In inductance.
At first, they resist changes in current.
After the current stabilizes, the voltage across them drops to near zero, and in a steady state DC
conditions, they also consume very, very little power, but again, not zero.
Now this their energy in magnetic field.
And also we have the resistors.
Resistors basically always always allow current to flow.
Resistors do not store energy.
And resistors continuously convert electrical energy into heat which is basically heat is basic means
inefficiency in electrical circuits.
Now these in simple DC circuits only resistors are responsible for continuous power consumption.
These are not 100% percent efficient and not compare.
But compared to this, capacitors, resistors, capacitors and inductors consume little power.
But resistors basically turns your energy into heat.
Now let's dig deeper into how resistors dissipate power.
Now we will start from the basic power formula we have learned so far.
You will use this formula a lot.
Multiply by I.
Now this is let's substitute the Ohm's law which remember Ohm's law was v equals I multiplied by r.
So basically what we will do is p equals I multiplied by I r p.
And this is equals to power Our two and R, or alternatively, what we can get is we can substitute
I and V and we will get I, v, I and p v power R.
And the important takeaway from this formula is.
Power increases with the square of the current, and power also increases with the square of the voltage
here.
Now this explains why modern electronics often aim to reduce current levels, because even a small increase
can cause a large increase in heat and energy loss.
And the real world considerations is in real circuits, non component is perfectly ideal.
As I said capacitors have a small internal resistance known as e S.
R.
This basically means equivalent series resistance.
Resistors have a bit of inductance due to their physical structure, and inductors have some unintended
capacitance.
And at high frequencies, like those used in a wireless communication or modern processors, these secondary
effects becomes very important here because the CPUs are so fast, right?
So when you design circuits, you need to account for these effects.
So make sure everything works correctly efficiently and stays cool.
Now that we have discussed passive components, it's time to meet the real hero of modern electronics
the transistors.
Now, transistors are not a passive components.
They are active components, meaning they can control the flow of electrical current electronically.
So you may ask here why are they important.
Now they can act as switches that turn on and off rapidly.
They can act as amplifiers that boost signals, and they are the building blocks of all modern logic
circuits today.
Now, without transistors, we will not have computers, smartphones, or any modern digital technology.
And before transistors, early computers used a mechanical switches to build logic circuits.
Now let's walk you through a simple mechanical not gate using a push button switches.
Now we have.
The two switches are wired in series between 5V and 0V.
Now the top switch is normally closed and the bottom switch is normally open.
And when x equals zero, which basically means no buttons pressed, the top switch stays closed and
the bottom switch stays open and the output is going to be five volts.
This is logic one.
And when the x is one the top switch opens which x equals one basically pressed.
And yeah the bottom switch stays.
Bottom switch closes and the output is zero volts.
So a not gate made from two push button switches.
The circuit inverts the input.
It acts exactly like a not gate in a digital logic.
However, mechanical systems had a major drawbacks.
They were slow, they wore out over time, and they were large and bulky.
Now, clearly a better solution was needed and the solution was electronic transistors.
Transistors completely changed the game here.
So modern transistors, which had a switch on or off in a billionth of a seconds or nanoseconds, and
modern transistors are so small that millions of them fit on a single CPU or chip, and they use extremely
like extremely low amounts of power.
They allow digital logic to be implemented faster, smaller, and more efficiently than ever before,
and voltage levels are typically five volts or sometimes 3.3V or 1.8V.
Now, if you go to your computer's Bios, uh, in the CPU setting, you can see these voltages.
Exactly.
These voltages, uh, what these are.
So this in modern transistors, these voltages basically mean one and zero volt basically means zero
And by switching between these two states electronically in a very fast, very, very, very fast transistors
performs all the calculation and data processing that make digital devices work.
So what you will learn in next lectures is in the next lecture, we will explore the two critical types
of transistors used in digital circuits.
Uh mosfet mos fet basically means uh metal oxide semiconductor field effect transistors and CMOs, which
is complementary metal oxide semiconductor.
Now, these technologies enabled today's computers and smartphones to be fast, small, and energy efficient.
Now, uh, thank you for watching this, uh, lecture.
And get ready to dive into the world of modern transistors, which is a very interesting topic here.