In our previous lectures, you learned about Boolean algebra expressions and how to implement them using
logic gates.
And in this lecture, you will learn how to implement logic gates directly in a hardware.
Now transistor we will start with transistors here.
These are solid state electronic devices that act as tiny electronic switches controlling the flow of
electrical signals.
Now, we have already discussed the idea of on off switches here in our previous lectures conceptually.
And now we will explore how these switches are physically built.
Now, to help you fully understand how transistors operate, we will start with a simple and clear introduction
to basic electronics.
And after that you will see how transistors can be connected together in pairs or groups to make faster,
more efficient switches that use less electrical power.
And finally, we will discuss some practical tips and considerations when using transistors to build
actual logic gates.
Now you don't need to be an electrical engineer to understand how logic gates are built at the hardware
level.
However, having a basic understanding of how few simple electronic concepts will make learning much
easier.
Now, in this lecture, we will provide you with a quick and friendly overview of the key concepts you
need to know.
And let's begin with the two fundamental definitions.
What is current now?
Current refers to the movement of electrical charge.
Electrical charge is measured in units called coulombs, written as Si.
Now, if a flow of one coulomb of charge passes a point in one second, which is one coulombs second,
that flow is defined as one amp, ampere or uppercase A, often simply called as amp.
Now current can flow through an Electrical circuit.
If there is a completely connected path from one side of the battery or some power source to the other,
if the circuit is broken at any point, no current can flow.
Voltage.
Also called potential difference, which refers to the difference in electrical energy per unit charge
between two points in an electrical circuit.
Now, one volt is defined as the potential difference between two points.
When a current of one ampere flowing through a conductor results in the dissipation of one watt of power.
In simple words, voltage is like the pressure pushing the electrical current through the circuit.
A computer at its lowest level, it's made from a combination of different electronic components.
Here are the main types the power sources.
These provide the electrical power needed to run the circuits.
Passive components.
These affect current flow and voltage levels, but cannot be controlled or changed by other electronic
components.
Examples include resistors and capacitors.
Active components.
These are components that can switch between different states like on, off, or other configurations
under the control of other electronic signals.
Transistors are the most important active components.
Conductors.
These are materials, usually wires, that connect all the components together and allow electrical
signals to flow.
Next, we will dive deeper into how each of these components behaves and how they are used to create
real working logic gates inside your computer.
In almost all countries, electrical power comes in the form of alternating current a c.
Now for AC, a plot of the magnitude of the voltage versus time shows a sinusoidal wave shape.
Now, computer circuits use direct current DC power, which, unlike AC, does not vary over time.
As you can see here, the AC has sinusoidal, but the DC has just a long line.
Now, if a power supply is used to convert AC to DC as shown in this diagram here.
Now batteries also provide DC electrical power when drawing circuits.
We use the symbol for a battery to designate a DC power supply.
The power supply in the example provides five volt DC five v DC.
And here you can see here it's a circuit symbol for five volt DC.
Now in our previous lectures you have seen that everything that happens inside the computer is based
on a system of ones and zeros.
But you may ask here how are these ones and zeros physically represented?
Now computer circuits distinguish between two different voltage levels to represent logical zeros and
logical ones.
Now logical zero for example may be represented as zero volt DC as this means logical 0 or 5 v DC as
a logical 1 or 0 v The sea as logical 0 or 3.3 V, which is common in computers.
One logical one here.
Now the reverse could also be implemented like the five v DC as logical 0 or 0 v, this as logical one.
Now the only requirement is that the hardware design remains consistent throughout.
Now luckily programmers don't need to worry about the actual voltages used.
This is handled by the computer hardware engineers, which in future I hope it will be you.
Also, keep in mind that electronic devices are designed to operate reliably within a certain range
of voltages.
Now, for example, a device, for example, meant to a device meant to operate at a nominal five volts
typically has a tolerance of plus or 5%, which meaning it can safely operate between 4.75V.
True, maximum volt is going to be 5.25V.
Now, the components inside the computer circuit are constantly switching between these two voltage
levels.
Now each switch takes a tiny amount of time, and this time limits how fast a circuit can complete operations.
As you will see later in the transistors lectures now, trying to switch faster requires more electrical
power, which creates heat.
Now, excessive heat can damage the components and limits the overall speed and calculations, and the
time dependent behavior of electronic components is critical.
Design concentration for hardware engineers.
Now next, we will dive deeper into how each of these components behaves and how they are used to create
real working logic gates inside your computer.