That I would have assumed that conductor phenomena there would be a performance with AC and DC commands
will be discussed.
Dire times basic led and Xena.
This is the basic symbol of the road.
Uh.
That line indicates that this is the cathode.
And this is the unbound that is a device that allows current to flow in only one direction.
There are specialized diodes the light emitting diode under the order that will be discussed later.
However the basic principle is the same here.
The current will flow in one direction.
If current flows flow attempt in the opposite direction the flow will be blocked diode finds.
Find use and money electronic circuits nowadays.
Um.
Now let's see the diode the semiconductor phenomena electrons in a metal frame form a sea of electrons
that are pitifully free to move about semiconductor materials like silicon and germanium have fuel free
electrons impurities added to semiconductor material can either add the free electrons or create an
absence of electrons which has holes.
So if we looked at this uh small schematic This is the UN type and this is the B type which which has
holes and type are electrons as you can see here they are equivalent columns excellence and holes.
This is the castle this.
This is the anode and this fundamental is that the depletion vision of the junction of the dialogue.
Consider the part of silicon at the right one side of the bar is daubed with negative material excess
electrons the cathode while the other side is daubed with a positive material existence all the anode
in between is a no man's land called the B and junction.
This is the depletion and the depletion is in this is that the injunction that forms are diode.
Now if we're locked here consider now applying negative voltage to that anode and I was the voltage
to the castle.
If we did that that is reversed reverse bias.
Meaning no current will flow and this region will be our much wider which means that the four electrons
will pass or more electrons at all.
This is the reverse bias of the diode y in this manner.
If we conducted a negative portion of four electron concerning our buying a positive for the note and
negative vote to take I thought that it is followed by us meaning current will flow.
Since this area is minimized and the electrons applied here allow these electrons to go to that junction
and the positive law applied here allows Hall to go to this side.
This will make that area that depletion area as small as possible which will allow current to flow.
Now if we look at this circuit setup the circuit illustrated on the Pluto brick ball as a store diode
and a battery and sure to note the cathode banded end of the diode the cathode is connected that it
is to use a 330 armed to the store that is the store and the circuit is our current limiting resistor.
So we are using it to limit current so that it won't blow the diode now set up the circuit illustrated
and the prototype.
And sure to know the cathode the Comfort is now connected the battery negative terminal and unless connected
there is a store and examined the difference between these two circuits um billed as there is a circuit
much of the voltage drop across the day that is forewarned by us it will equal Boyne 7 which is the
amount of all that is required to build uh a fourth wall by US situation for the diode.
This is the simplest model to say this.
Now if AC is applied to a diode during one half of the cycle that is followed by us and current flows
during the other half of the cycle that diode is reversed by us and stops come.
This is the process of rectification allowing current to flow and only one direction.
It's commonly used in changing AC into DC.
As you can see here this is the AC signal and this is the output that I wrote.
It only allows um AC to flow as you can see the positive portion of the signal on the floor.
The negative is zero since it's reversed biased for the diode.
Uh this is commonly used in the rectification circuit for turning AC signals to DC signals.
Now let's look at the light emitting diode in normal diodes when electrons combines with holes heat
is produced while some material when electrons combine with holes photons of light are emitted LEDs
are generally used and as indicators throw they have the same realities as a regular diode but instead
state of dissipating here they are submitting light.
This is a simple circuit that can light lightly build at a certain circuit on the brutal board the longer
let lead is the anode and the diode you will see two leads a long one and a short one long is the positive
and the short is the negative the reverse the lid and observe what other now you need to reverse that
led and observe what will happen.
You'll note that 20 alone the current limiting it is a storm not only limits the current but also controls
lid brightness.
So if we place the 7000 on uh resistor the light will be damned if we placed 100 under this too.
The light will be uh that it would be brighter.
Next we will look at Xena of the old okay.
This is the symbol of the Xena of the eurozone diode is designed through appropriate the dubbing so
that it can conduct an ability to mind the reverse voltage so the difference between it and normal doubt
is that it does operate in the reverse direction that it begins to conduct and then maintains that the
to mind voltage that over voltage and associated current must be dissipated by the diode as heat.
As you know that is constructed so that it will conduct one reversed by us above certain voltage.
The Axis voltage and current dean is conducted to ground and the energy is dissipated as heat as you
know acts as a symbol voltage regulator.
In the case involved source as you can see here is bus throw count limiting resistance to drop the voltage
somewhat.
To take the brush out of the scene.
If the xenon was not in place the amount of voltage drop across that of the store would depend on the
amount of carbon being down from the circuit.
With this as it was you know in place the four point seven Volt would be maintained by the xenon acting
as a bath for the excess.
Come on that is not being drawn off of this excess current has to be dissipated as here.
Therefore there are current limits on the and others that the designer need to consider.
That's it for uh diodes.
Next we will uh discuss transistors and more details.
Thanks for watching.
This is education engineering team.