VI Characteristics of PN Junction Diode | PN Junction Forward Bias | PN Junction Reverse Bias
Summary
TLDRThis educational video delves into the voltage-current (V-I) characteristics of PN junction diodes. It explains the formation of ions at the junction of P-type and N-type semiconductors, creating an electric field that impedes current flow. The tutorial covers forward bias, where applying a voltage greater than the potential barrier allows current flow, and reverse bias, where an increased voltage widens the depletion region, preventing current flow except for a minimal leakage from minority carriers. The video concludes with a caution about the potential damage to the diode due to high reverse bias voltages.
Takeaways
- 🔬 When P-type and N-type semiconductor materials are diffused together, a space charge region or depletion region is formed at the junction with positive and negative ions.
- 🔋 The formation of ions at the junction is due to the combination of holes from P-type material and electrons from N-type material, resulting in an electric field that prevents current flow.
- 🔌 In forward bias, the anode should be connected to the positive terminal and the cathode to the negative terminal of the battery, which narrows the depletion region width and allows current to flow.
- 📈 The forward bias characteristic of a PN junction diode shows that current starts to flow when the forward voltage exceeds the threshold voltage, which is approximately 0.7V for silicon and 0.3V for germanium diodes.
- 🔌 In reverse bias, the anode is connected to the negative terminal and the cathode to the positive terminal of the battery, increasing the depletion region width and preventing current flow.
- 📉 The reverse bias characteristic of a PN junction diode shows that current does not flow until a breakdown voltage is reached, after which a large current can flow, potentially damaging the diode.
- 💡 The small current that flows in reverse bias is due to minority charge carriers, which is referred to as reverse saturation current.
- 🚫 If the reverse bias voltage is increased beyond a certain value, the diode may experience a breakdown, leading to a significant increase in current and potential diode damage.
- 📚 Understanding the VI characteristics of a PN junction diode is crucial for comprehending its operation in electronic circuits, including how it behaves under different bias conditions.
Q & A
What happens when P-type and N-type materials are diffused together?
-When P-type and N-type materials are diffused together, a space charge region or depletion region is formed at the junction. This region contains ions, with negative ions on the P-type side and positive ions on the N-type side.
How are ions generated at the junction of P-type and N-type materials?
-Ions are generated at the junction because when P-type material, which has holes, and N-type material, which has electrons, are diffused, the electrons and holes combine. This combination results in the formation of negative ions on the P-type side and positive ions on the N-type side.
What is the role of the electric field formed by the ions in a PN junction?
-The electric field formed by the ions in a PN junction prevents the flow of current until the depletion region is nullified by increasing the forward bias voltage beyond the threshold voltage or potential barrier voltage.
What is the effect of forward bias on the depletion region in a PN junction?
-In forward bias, the depletion region width decreases as the forward voltage increases, allowing current to flow through the PN junction once the voltage exceeds the threshold voltage.
What is the threshold voltage for a silicon diode in forward bias?
-The threshold voltage for a silicon diode in forward bias is 0.7 volts.
What is the threshold voltage for a germanium diode in forward bias?
-The threshold voltage for a germanium diode in forward bias is 0.3 volts.
What happens to the depletion region when a PN junction is reverse biased?
-When a PN junction is reverse biased, the depletion region width increases, preventing the flow of current through the junction.
What is the characteristic of current flow in reverse bias for a PN junction?
-In reverse bias, the current does not flow through the PN junction unless the reverse bias voltage exceeds a certain value leading to breakdown, at which point a large current flows.
What is reverse saturation current and what causes it?
-Reverse saturation current is the small current that flows in reverse bias due to minority charge carriers. It is very minimal and occurs even when the depletion region width increases in reverse bias.
What is the potential risk of applying a reverse bias voltage beyond the breakdown voltage in a PN junction?
-Applying a reverse bias voltage beyond the breakdown voltage can lead to a large current flow, which may damage the PN junction due to the high current.
How can one determine the forward and reverse bias characteristics from the IV curve of a PN junction?
-The forward bias characteristic is in the first quadrant of the IV curve, where current flows after the potential barrier is overcome by the forward voltage. The reverse bias characteristic is in the third quadrant, where current does not flow until breakdown occurs.
Outlines
🔬 Understanding PN Junction and Its Formation
This paragraph delves into the fundamentals of PN junction diodes, explaining how they are formed by diffusing P-type and N-type semiconductor materials together. The speaker clarifies that ions are generated at the junction due to the combination of holes from the P-type material and electrons from the N-type material. These ions create an electric field that prevents current flow unless a certain voltage is applied. The explanation sets the stage for understanding the voltage-current (V-I) characteristics of diodes, which is the main focus of the video.
📈 Exploring the V-I Characteristics of PN Junction Diodes
The second paragraph focuses on the V-I characteristics of PN junction diodes, particularly under forward and reverse bias conditions. In forward bias, the anode is connected to the positive terminal and the cathode to the negative terminal of a battery, narrowing the depletion region and allowing current to flow once the voltage exceeds the threshold or potential barrier voltage. For silicon diodes, this threshold is 0.7 volts, and for germanium, it's 0.3 volts. In reverse bias, the anode is connected to the negative terminal and the cathode to the positive, widening the depletion region and preventing current flow except for a small leakage current due to minority carriers. The speaker warns that exceeding a certain reverse voltage can lead to diode breakdown and significant current flow, which can damage the diode. The paragraph concludes with a brief overview of the forward and reverse bias characteristics, emphasizing the importance of understanding these behaviors for practical applications.
Mindmap
Keywords
💡PN Junction
💡Depletion Region
💡Forward Bias
💡Reverse Bias
💡Ions
💡Space Charge Region
💡Potential Barrier
💡Threshold Voltage
💡Breakdown Voltage
💡Minority Carriers
Highlights
Explanation of PN Junction diode and its VI characteristics.
Formation of ions at the junction of P and N type materials.
Generation of negative ions in P type material and positive ions in N type material.
The role of holes and electrons in the formation of ions at the junction.
Creation of an electric field due to the presence of ions, which prevents current flow.
Description of forward biasing a PN Junction diode.
Narrowing of depletion region width under forward bias.
Requirement of forward voltage to be greater than potential barrier voltage for current flow.
Threshold voltage for silicon diodes is 0.7 volts, and for germanium diodes, it is 0.3 volts.
Current starts to flow in forward bias once the voltage exceeds the threshold.
Explanation of reverse biasing a PN Junction diode.
Increase in depletion region width under reverse bias, preventing current flow.
Minority carrier-induced current flow in reverse bias.
Potential for diode damage due to high current flow post breakdown in reverse bias.
Characteristics of PN Junction diode in forward and reverse bias.
Reverse saturation current due to minority carriers in reverse bias.
Summary of the basic characteristics of PN Junction diodes.
Transcripts
Hello friends welcome to engineering
Funda family in this video I'll be going
to explain you p and Junction diode VI
characteristics in my last video I have
explained PN Junction diode there are a
few basic things that you need to
understand before you go for Vi
characteristic see when you diffuse P
type and end type material together then
at
Junction there is space charge region or
region in this region there are ions see
at the side of P type material we have
negative ions and at the side of n type
material we are having positive ions now
question is how these ions are
generated see with P type material we
don't have ions with n type material we
don't have ions but when you diffuse P
type and N type material at that time at
Junction there is a formation of ions at
the side of P type negative ions are
generated at the side of n type positive
ions are generated but why see when you
diffuse materials at that time P type
material is having holes n type material
is having
electrons so electrons and holes are
getting combined together so P type
material is having holes and that is
taking that is consuming electrons and
as it consumes electron it is forming
negative ions over here and N type
material is having electrons it is
consuming holes so it is forming
positive ions over here right so you'll
be observing when you diffuse two
materials together at that time there is
a formation of ions at the side of P
type it consumes electrons means
negative charge that's why it forms
negative ions and N type material is
having electrons it is consuming holes
that's why it is forming positive ions
holes is is having positive charge
that's why it is forming positive ions
over here and this ions are resulting
into electric field and this electric
field will not allow flow of current
this electric field will not allow flow
of current see this electric field is
happening because of depletion region in
depletion region we are having positive
and negative ions so because of ions
there is electric field and that
electric field will not allow flow of
current right now let me explain how PN
Junction VA characteristic is there so
in PN Junction see if you want forward
bias characteristic then anod should be
connected with positive terminal of
battery and cathode that should be
connected with negative terminal of
battery so when you connect anode with
positive and cathode with negative you
will be connecting this PN Junction in
forward bias now in forward bias what
happens so in forward bias you'll be
observing depletion region width that is
getting
narrowed so width of depletion region
that will decrease as you increase
voltage right you see here we are having
depletion region without any bias means
here we have not connected any Supply
now we are connecting that in forward
wise for forward wise what we need to do
anod with positive and cathode with
negative Minal so in this situation
depletion region width you see that is
decreasing over here so previously
depletion region WID that was bit wide
but as you increase forward V voltage
the depletion region width is decreasing
right and this depletion region that
doesn't allow flow of current so but
obviously for a flow of current for a
flow of current this battery is
connected so here this battery will be
resulting into current in this direction
but this current through this PN
Junction will not flow until depletion
region width so we need to nullify
depletion region how by increasing
forward W voltage
Beyond threshold voltage or you can say
forward W voltage should be greater than
potential barrier voltage so as you
increase as you increase this forward W
voltage as you increase this forward wi
voltage depletion region width will
decrease and if you increase this
forward wi voltage Beyond potential
barrier then you'll be observing this
depletion region that will get nullified
after that flow of current will happen
in this diode in this Loop right so now
let us try to understand characteristic
of p and Junction in forward Bas so see
initially we are increasing voltage but
as depletion region is there flow of
current will not
happen right but if you increase voltage
Beyond threshold volt voltage then
current will start to flow so you can
observe vertically we have current
horizontally we have voltage so if you
increase if you
increase this voltage Beyond threshold
voltage then current will flow right so
here see this voltage after which
current is Flowing that is theold
voltage so that is 0.7 volt in case of
silicon diode and that is 0.3
in case of germanium diode so that is
how simple characteristic is there with
PN Junction in forward Bas
right up to threshold voltage or up to
potential
barrier in forward B also current will
not flow if you apply voltage greater
than potential barrier then current will
flow right now let us try to understand
reverse bias characteristic so in
Reverse bias what we need to do is we
need to
connect anode with negative terminal of
battery and cathode with positive
terminal of battery so what will happen
as if you connect this PN Junction in
Reverse bias the depletion region width
will
increase it will increase
further so what will happen you see as
depletion region width is increasing
current cannot flow right current in
this diode cannot flow see because of
battery current should flow like this
right current should flow like this but
as depletion region with that is getting
widen it will not allow flow of current
it will not allow flow of current so
current cannot flow over here right let
me show you in characteristic you see
this is voltage and this is what reverse
bass so characteristic will come in
third quadrant right so in Reverse bias
if you increase voltage then you see
current will not flow right here current
will not flow now you going be thinking
like I'm showing you some current right
constant current you
see so here this
current this current that is happening
this current that is happening because
of minority carrier right so here
minority charge carrier allows flow of
current but that is very less right and
see if you increase this Reverse by
voltage
Beyond some value then there can be
breakdown right so after breakdown after
breakdown huge current will flow right
after breakdown huge current will flow
so if I say this is breakdown
voltage right then after breakdown you
see huge current will flow and in this
situation it is highly possible that P
and Junction may get damaged right so
here see in Reverse bias current cannnot
flow and whatever current current that
flows that is due to minority charge
carriers only right and here in Reverse
B depletion region width that will
increase and it will increase based on
reverse bias voltage right and after
some value there will be breakdown and
huge current will flow so here see
complete characteristic that I have
shown see in forward bias this is
forward characteristic in forward West
all you need to have is you need to have
anod you need to have
anode positive with respect to cathode
right so characteristic will be in first
Quant in which see after potential
barrier forward as voltage current will
flow and in Reverse bias in Reverse bias
anod will be negative right
anod will be negative with respect to
cathode right so in that case current
will not flow right and whatever current
that is happening here that is due to
minority carrier that one can say that
is reverse saturation current right
reverse saturation
current that is happening because of
minority carrier that is how basic
characteristic is there with P Junction
that I hope you have understood this
still if anything that you would like to
share please note it down in comment
section I'll be happy to help you thank
you so much for watching this video
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