If I were to ask you
what the most important advancement humankind has ever made,
What would you say?
Many would make the case for fire,
our species was in an evolutionary rut
until we harnessed it’s power.
It gave us the warmth to survive harsh winters,
its light extended our day,
it’s destructive powers gave us a weapon against predators
and it allowed us to cook our food which allowed our brains to grow.
Our discovery of fire
transformed not only our technologies, but our culture and way of life.
But I would argue that we are currently living
in a time of equal or even greater change.
We are living in an time of incredible growth,
one that has already started to transform
the way we live our lives.
The age of information.
With 40% of our world’s population currently connected to the internet,
the human race is more intertwined than ever before.
But what led to this amazing tool?
What single invention gave rise to our smartphone equipped generation?
The transistor is information itself,
even this video is just a series of ones and zeros
beaming across the planet to be interpreted by the processors in your computers.
Without the transistor,
I wouldn’t have access to the wealth of information online to do my research,
I wouldn’t be able to use my animation software to make these videos,
and I most certainly wouldn’t have been able to share it here for the world to see.
The transistor is so simple,
but it is the foundation for all our modern computers.
To understand its impact we need to
understand the history and science behind it.
Before the transistor existed, we used vacuum tubes,
which were these bulky evacuated glass bulbs.
The triode vacuum tube consisted of three parts,
the cathode, grid and anode.
A current is passed through the cathode and it begins to heat up,
causing it to release electrons,
As the gases have been removed from the tube,
the electrons have very little resistance to their movement,
and they are attracted to the positively charged anode.
This completes the circuit and a current flows.
But we can manipulate this flow of electrons
in many useful ways with the grid.
For example we can use it as a switch,
if we place a light bulb here it will only light
up when there is a positive voltage acrossthe grid.
If we apply a negative voltage the
negative charge will repel electrons tryingto pass through.
This is the foundation for binary coding
which is the 1s and 0s that gave birth to the age of information.
在这里 1是正电压 0是负电压
Here, 1 is a positive voltage and 0 is a negative.
1 turns the light on, 0 turns it off.
The world’s first general purpose electronic computer,
The ENIAC, used 18 thousand vacuum
tubes to perform calculations.
Designed by John Mauchly & J. Presper Ekert,
it was completed in 1945.
It was purpose-built to calculate trajectories for artillery during world war 2.
A calculation that would take a human a day to calculate,
took ENIAC 30 minutes.
But this thing weighed 30 tonnes and took up an entire room.
It was incredibly power hungry,
as the vacuum tubes cathodes needed to be heated to work,
which also meant that the
vacuum tubes burnt out regularly and needed to be replaced.
All this to perform a function that
your phone basically does within Angry Birds.
Today, its computing power could be contained on a silicon chip
no larger than a grain of sand, and that
is thanks to the transistor.
A modern phone has around 2 billion transistors, which perform
the exact same job as the vacuum tube, but on a nanoscale.
Let’s look at how it works.
Many of you will recognise the transistor as one of these,
but this is a through hole transistor
that you can buy from hobby electronics stores for your DIY projects.
The transistors in your CPU are microscopic and are manufactured
with incredible precision with machines on
thin wafers of silicon crystal that are sliced off silicon ingots, like this.
So what makes silicon so special
that an entire section of the San Francisco Bay area
has been nicknamed after the material?
Silicon is a semiconductor,
which means that its conducting properties can be tailored
by introducing impurities to the crystal structure.
Silicon has 4 electrons in it’s valence shell,
this is the outermost orbit for electrons,
and it determines many of the chemical properties of the atom.
Atoms want 8 electrons in that shell,
as this makes them very stable.
So silicon readily forms covalent bonds to 4 neighbouring silicon atoms
to gain those extra electrons.
Now if we introduce those impurities to this pure silicon crystal,
we can change how it conducts a current.
If we add phosphorus,
which has 5 electrons in it’s valence shell,
the extra electron is left free to roam the crystal structure.
This extra electron makes the N-type negatively charged,
which is where the name comes from.
The P-type is positively charged
because it is doped with boron, which has three electrons in its valence shell.
This structure wants to gain its final electron,
and will steal electrons from its neighbouring atoms.
this creates a mobile positive charge, called a hole.
The conductivity of the material has thus been increased
as we have increased the number of mobile charges.
When we arrange n-type and p-type semiconductors
like this and attach terminals to each, we
create the world’s most prevalent transistor.
The NPN transistor.
The transistor works due to the interaction of those free electrons and holes
at the n-type and p-type junction.
Free electrons in the n-type will migrate
over to fill those holes in the p-type.
This creates a boundary layer called the
depletion layer which prevents more electrons passing through,
due to the negative charges repellingeach other. But,
when a positive voltage is applied to the base
it negate that depletion layer and allows current to flow through,
completing the circuit.
As you can see,
this is very similar to the function of the vacuum tube.
So how exactly does this allow computers to
perform all these complex functions that wesee today.
Let’s look at a very basic example.
Let’s add two numbers together.
First weneed to learn how numbers are represented
in binary, that’s the 1’s and 0’s that are used to store data.
This is the number 15,
which is the largest number you can represent with 4 bits..
The first bit represents 1,
第二个代表2 然后是4 最后是8 加起来就是15
the next represents 2, then 4 and finally 8, added up that equals 15.
This pattern continues with each successive bit representing double the previous,
so if we add an additional bit
we can count up to 31.
Let’s add 5 and 6 together.
To do this we want a circuit
that will hold a 1 in this position when either are 1
and carry the 1 forward when both are 1,
as you can see this will give us the number 11.
the simplest circuit that can do this is a half adder
Which contains two types of logic gates,
these are devices that can modify the binary code, they are
built using transistors.
The first is the XOR logic gate,
which gives a 1 only when one of the inputs is one,
if both are 0 or 1 it gives a 0.
The second Logic gate is an AND gate, which gives a 0 for everything
except when both inputs are 1.
If we wire these logic gates like this we create a half adder,
which gives two outputs our Sum and our Carry.
Which allows us to add our binary number one bit at a time.
A more complicated circuit is needed to perform the calculation in one step.
Modern computers can perform millions of these calculations per second and they are still
getting faster. The Co-founder
of Intel Gordon E. Moore noticed a trend in 1965 that the
density of transistors on integrated circuits doubles every two years,
that trend has held until very recently
but it is starting to slow down.
One of the reasons for this is the less well known of Moore’s predictions, Moore’s second law or Rocks law,
which states that the cost of manufacturing these devices will double every 4 years.
Intel made an announced last year
that the rate of advancement was slowing for these reasons
it’s getting more and more difficult for chip manufacturers
to shrink their product while maintainingprofit.
Another problem that transistors are facingis quantum tunneling.
As these transistors get smaller, so do the barriers between different sections.
The barriers between each section of the transistor are getting so thin,
that electrons can pass right through them.
With no definitive successor to the silicon transistor lined up
this incredible period of growth over the last 50 years could plateau in the near future.
Some want to harness quantum mechanics
to perform calculations faster than any transistor ever could,
others want to decentralise computing power with the so calledinternet of things.
Intel have said themselves
that they plan to shift their focus from increases
in speed to decreases in power consumption.
One thing is for sure,
the computer industry will have to redefine itself in the near future.
Thanks for watching!
Thanks to your incredibleresponse to their last sponsorship
TheGreatCoursesPlus have sponsored me once again.
So thank youto all my subscribers, patreon supporters
and TheGreatCoursesPlus for helping Real Engineeringexist.
If you enjoy my videos,
you will definitely like TheGreatCoursePlus.
They have over 7000 different lectures from world renowned educators.
They have a huge range of topics,
if you would like to learn more about electronics they
even have a course for that or you can learn
你还能在那里学习摄影 象棋 烹饪等
about photography, chess and cooking.
These courses give you indepth knowledge of a variety of subjects,
while allowing you to learn at
your own pace without tests or exams.
You can get a free one month trial
by going to the TheGreatCoursesPlus.com/RealEngineering
If you would like to see more content or support
real engineering the links for my Patreon, Instagram,
Facebook and twitter accounts are below.