Introduction to Bipolar Junction Transistor (BJT)

Summary

This video from the 'All About Electronics' YouTube channel offers an insightful introduction to Bipolar Junction Transistors (BJTs), exploring their fundamental role in modern electronics and their operation as switches or amplifiers. The script delves into the construction of BJTs, detailing the emitter, base, and collector regions, and explains the NPN and PNP configurations. It outlines the three primary operating regions of BJTs: Active, Cut-off, and Saturation, and touches on the Reverse Active Region. The explanation of current relationships and the transistor's function as a current control device highlights its importance in signal amplification, setting the stage for further exploration in upcoming videos.

Takeaways

• 🌟 The Bipolar Junction Transistor (BJT) is a foundational semiconductor device that has enabled the development of modern electronics, including computers and integrated circuits.
• 🔌 BJTs have three terminals: the Emitter, Base, and Collector, and can function as a conductor or insulator based on the input signal, making them useful as switches or amplifiers.
• 📶 BJTs are categorized as either NPN or PNP types, depending on the doping of the Emitter, Base, and Collector regions with N-type or P-type impurities.
• 🔄 The term 'bipolar' refers to the involvement of both electrons and holes in the current flow within the BJT.
• 🔩 Internally, the BJT consists of two PN junctions, with the Emitter being heavily doped to supply electrons, the Base lightly doped, and the Collector moderately doped.
• 📉 The Base region is the narrowest of the three regions, facilitating the majority of electrons to pass into the Collector rather than recombining in the Base.
• 🛠 BJTs can operate in different regions: Active, Cut-off, Saturation, and Reverse Active, each with specific biasing conditions for the Base-Emitter and Base-Collector junctions.
• 🔄 In the Active Region, the Base-Emitter junction is forward-biased, and the Base-Collector junction is reverse-biased, allowing current to flow from the Emitter to the Collector.
• 🔗 The current relationship in a BJT is defined by the equation 'IC = β × IB', where 'β' is the current gain and typically ranges from 50 to 400, indicating the BJT's ability to amplify current.
• 🔧 BJTs can be configured in common Emitter, common Collector, or common Base arrangements, each with distinct advantages and applications in electronic circuits.
• ⚡ The BJT's operation in the Active Region involves the movement of electrons from the Emitter, through the thin Base, into the Collector, where they are attracted by the positive terminal of the Collector supply voltage.

Q & A

What is a Bipolar Junction Transistor (BJT)?

A Bipolar Junction Transistor (BJT) is a three-terminal semiconductor device that can act as a conductor or insulator based on the applied input signal. It plays a crucial role in various electronic devices, including digital electronics as a switch and analog electronics as an amplifier.

What are the three regions of a BJT?

The three regions of a BJT are the Emitter, the Base, and the Collector. These regions are doped differently, which determines the transistor's type as either NPN or PNP.

What is the significance of the term 'bipolar' in BJT?

The term 'bipolar' in BJT indicates that both electrons and holes contribute to the flow of current, making it different from other types of transistors that rely on a single type of charge carrier.

How many PN junctions are present in a BJT?

There are two PN junctions in a BJT: one between the Emitter and the Base, and the second between the Base and the Collector.

What are the three regions of operation for a BJT?

The three regions of operation for a BJT are the Active Region, the Cut-off Region, and the Saturation Region. Each region has specific biasing conditions that determine the transistor's behavior.

What is the difference between the Active Region and the Cut-off Region in a BJT?

In the Active Region, the Emitter-Base Junction is forward-biased, and the Base-Collector Junction is reverse-biased, allowing current to flow. In contrast, in the Cut-off Region, both junctions are reverse-biased, and ideally, no current flows.

What is the function of the Emitter in a BJT?

The Emitter in a BJT is heavily doped and its function is to supply electrons. It is the source of the majority charge carriers that contribute to the current flow in the transistor.

How does the width of the Base region affect the operation of a BJT?

The Base region is much narrower compared to the other two regions. This allows most of the electrons from the Emitter to pass through the Base and into the Collector, which is essential for the transistor's amplifying action.

What is the current gain (beta) of a BJT and why is it important?

The current gain (beta) of a BJT is the ratio of the Collector current to the Base current (IC/IB). It is important because it indicates the transistor's ability to amplify current; a higher beta means greater amplification.

What are the three configurations of a BJT and what determines their use?

The three configurations of a BJT are the Common Emitter, Common Collector, and Common Base. The choice of configuration depends on the specific requirements and application of the circuit, as each configuration has its own advantages and disadvantages.

How does a BJT amplify a signal in the Active Region?

In the Active Region, by controlling the small Base current (input), a BJT can control a much larger Collector current (output). This ability to control a larger output current with a smaller input current allows the BJT to amplify signals.

What is the relationship between the Base current, Emitter current, and Collector current in a BJT?

The relationship between the Base current (IB), Emitter current (IE), and Collector current (IC) in a BJT is given by IE = IB + IC, and since IC ≈ IE, it simplifies to IE ≈ IB + alpha * IE, where alpha is the fraction of Emitter current that flows through the Collector.

Outlines

00:00

🔌 Introduction to Bipolar Junction Transistors (BJTs)

The video begins with an introduction to the Bipolar Junction Transistor, a foundational semiconductor device that has paved the way for modern electronics, including computers and other gadgets. The BJT is a three-terminal device capable of functioning as a conductor or insulator based on the input signal, making it suitable for use as a switch in digital electronics or an amplifier in analog electronics. The video explains the structure of the BJT, highlighting its three doped regions: the Emitter, Base, and Collector, which determine whether the transistor is NPN or PNP type. The term 'bipolar' refers to the involvement of both electrons and holes in current flow. The internal construction details of the BJT are also discussed, emphasizing the different doping levels and widths of the regions, and their respective roles.

05:04

📶 BJT Operation Regions and Biasing

This paragraph delves into the different operational regions of the BJT: the Active Region, Cut-off Region, Saturation Region, and Reverse Active Region. The conditions for each region are explained, detailing the voltage relationships necessary for the BJT to operate in these modes. The Active Region is where the Emitter-Base junction is forward-biased, and the Base-Collector junction is reverse-biased, with specific voltage conditions provided. The Cut-off and Saturation Regions are also described, with the latter being where both junctions are forward-biased. The Reverse Active Region is mentioned as having a low gain and is generally avoided. The explanation includes the biasing conditions for both NPN and PNP transistors, emphasizing how the voltages should be arranged for each type to operate in the Active Region.

10:07

🔍 Internal Working of BJT in Active Region

The script explains the internal workings of an NPN BJT when it is operating in the Active Region. It describes how the Emitter, being heavily doped, supplies electrons, which are then pushed towards the lightly doped Base region when a biasing voltage is applied. Due to the thinness of the Base and its light doping, most electrons either recombine with the few holes present or pass through to the Collector region. The Base-Collector junction being reverse-biased aids in attracting these electrons towards the Collector. The movement of electrons and holes, along with the conventional current direction, is detailed, leading to the establishment of the relationship between Base current (IB), Collector current (IC), and Emitter current (IE). The current gain, denoted by beta (β), is introduced as a factor that relates the input Base current to the output Collector current.

15:11

🔗 Current Relationships and BJT as a Current Control Device

The final paragraph discusses the relationship between the Base current, Emitter current, and Collector current in a BJT, highlighting it as a current control device. The script establishes the formulae that relate these currents, showing that by controlling the Base current, one can control the Collector current, which is the amplified output. The role of alpha (α) and beta (β) in these relationships is explained, with beta being the current gain that typically ranges from 50 to 400 for different transistors. The BJT's ability to amplify the input signal when configured with a resistor between the Collector and Emitter terminals is also mentioned, setting the stage for further discussions on amplification and biasing techniques in upcoming videos.

Keywords

💡Bipolar Junction Transistor (BJT)

A Bipolar Junction Transistor (BJT) is a three-terminal semiconductor device used as a switch or amplifier. It operates based on the input signal applied, allowing it to act as a conductor or insulator. In the video, BJTs are explained as crucial components in digital and analog electronics, with two main types: NPN and PNP.

💡NPN Transistor

An NPN transistor is a type of BJT where the Emitter and Collector are doped with N-type impurities, and the Base with P-type impurity. This structure allows the transistor to conduct current when a positive voltage is applied to the Base relative to the Emitter. The video explains how NPN transistors operate, including their use in amplification and switching.

💡PNP Transistor

A PNP transistor is a BJT type where the Emitter and Collector are doped with P-type impurities, and the Base with N-type impurity. It conducts current when the Base is at a lower voltage than the Emitter. The video details the biasing conditions required for PNP transistors and their similar functionalities to NPN transistors in different circuit configurations.

💡Active Region

The active region of a BJT is where the Emitter-Base junction is forward biased, and the Base-Collector junction is reverse biased. In this state, the transistor can amplify signals. The video describes the voltage conditions needed to achieve this state and how it enables signal amplification in electronic circuits.

💡Cut-off Region

In the cut-off region, both the Base-Emitter and Base-Collector junctions are reverse biased, causing the BJT to act as an insulator with no significant current flow. The video explains this region as one of the operating states of BJTs, particularly when used as switches.

💡Saturation Region

The saturation region occurs when both the Base-Emitter and Base-Collector junctions are forward biased, allowing maximum current flow through the transistor. The video discusses this state as another operational mode of BJTs, essential for switching applications.

💡Doping

Doping refers to the introduction of impurities into semiconductor material to change its electrical properties. In BJTs, different doping levels in the Emitter, Base, and Collector regions create the NPN or PNP structures. The video explains the significance of doping in defining the transistor's characteristics and functionality.

💡Current Gain (Beta)

Current gain, or beta (β), is the ratio of the Collector current (IC) to the Base current (IB) in a BJT. It indicates how much the input current is amplified at the output. The video explains how beta affects the amplification process and typical values for various BJTs.

💡Forward Bias

Forward bias occurs when a positive voltage is applied to the P-type region relative to the N-type region, allowing current flow across a PN junction. In BJTs, forward biasing the Base-Emitter junction is essential for operation in the active and saturation regions, as explained in the video.

💡Reverse Bias

Reverse bias is when a negative voltage is applied to the P-type region relative to the N-type region, preventing current flow across a PN junction. The video discusses reverse biasing in the context of the Base-Collector junction, necessary for the transistor to operate in the active region.

💡Minority Charge Carriers

Minority charge carriers are the less abundant type of charge carriers in a semiconductor material. In an NPN transistor, these are holes in the N-type regions. The video mentions their role in the flow of current through the Base-Collector junction when it is reverse biased.

Highlights

The invention of the bipolar junction transistor (BJT) led to the development of many other semiconductor devices, including integrated circuits, which are essential for modern computers and electronic gadgets.

BJTs can function as a switch in digital electronics or as an amplifier in analog electronics due to their ability to act as a conductor or insulator based on the input signal.

BJTs are three-terminal semiconductor devices with three doped regions: the Emitter, the Base, and the Collector, which determine whether the transistor is NPN or PNP type.

The term 'bipolar' in BJT refers to the contribution of both electrons and holes in the flow of current.

BJTs contain two PN junctions with an interaction between the regions, unlike independent back-to-back diodes.

The Emitter in a BJT is heavily doped to supply electrons, the Base is lightly doped, and the Collector is moderately doped.

The Base region of a BJT is narrower than the other regions, facilitating the collection of electrons by the Collector.

BJTs can operate in three regions: Active, Cut-off, and Saturation, each defined by the biasing of the Emitter-Base and Base-Collector junctions.

In the Active Region, the Emitter-Base junction is forward biased, and the Base-Collector junction is reverse biased, with specific voltage conditions.

The Cut-off Region involves both junctions being reverse biased, while the Saturation Region has both junctions forward biased.

A Reverse Active Region exists but is generally avoided due to low gain provided by the BJT in this region.

PNP transistors operate differently in the Active Region compared to NPN transistors, with the Emitter voltage being greater than the Base voltage.

BJTs can be configured in different ways, such as Common Emitter, Common Collector, and Common Base, each with its advantages and disadvantages.

In the Active Region, the relationship between the Base current, Emitter current, and Collector current is defined by the current gain (beta) of the BJT.

BJTs are current-controlled devices, where controlling the Base current can regulate the Collector current, unlike field-effect transistors which are voltage-controlled.

The BJT's ability to amplify the input signal is demonstrated by the relationship between the input Base current and the output Collector current.

In addition to the Collector current due to the Emitter, there is a small reverse saturation current (ICO) in the Collector due to minority charge carriers.

The video promises to cover different configurations, input and output characteristics, and biasing techniques of BJTs in upcoming videos.

Transcripts

Hey, friends welcome to the YouTube channel  ALL ABOUT ELECTRONICS. So in this video, we  

will learn about the Bipolar Junction Transistor.  The invention of the transistor, led the invention  

of the many other semiconductor devices including  the integrated circuits. And in fact, due to these  

integrated circuits, the modern day computers,  and other electronic gadgets, which we are using  

is possible. So the bipolar Junction transistor or  the BJT is a three terminal semiconductor device,  

which can act as a conductor or insulator based  on the applied input signal. And due to this  

property, the transistor can be used as a switch  in the digital electronics. Or it can be used  

as an amplifier, in the analog electronics.  So nowadays, the field effect transistors,  

are widely used in the electronic industry. But  still the BJTs are extensively used. And anyone  

who is interested in the electronics, should  have some basic knowledge of this BJT. So in this  

bipolar Junction transistor, there are three doped  regions. The Emitter, the Base and the Collector.  

And based on the doping of these three regions,  it is known as either NPN or PNP transistor. So  

in case of the NPN transistor, both Emitter and  the Collector are doped with the N-type impurity,  

and the Base is doped with the P-type impurity. On  the other end, in the PNP transistor, the Base is  

doped with the N-type impurity, and the Emitter  and the Collectors are dope with the P-type  

impurity. And here, the term bipolar indicates  that, both electrons and holes contributes in the  

flow of current. Now if you look inside this BJT,  then there are two PN junctions. One is between  

the Emitter and the Base, and second is between  the Base and the Collector. And it appears as if,  

the two back-to-back diodes are connected in the  series. But actually, it won't behave like that.  

Because when we connect to back-to-back diodes,  then we are assuming that, there is no interaction  

between the two diodes. That means these two  diodes are operating independently. But in  

case of the BJT, actually there is an interaction  between the two regions. So if we connect the two  

back to back diodes like this, then it won't  behave like a BJT. Now if we talk about the  

internal construction of the BJT, then the Emitter  is heavily doped, and the function of the Emitter  

is to supply the electron. And in fact, that is  why it is known as the Emitter. Then if you talk  

about the Base, then it is lightly doped, and  the doping concentration of the Collector is  

between the Emitter and the Base. That means the  Collector is the moderately doped. And if we talk  

about the width of these three regions, then  the Base region is much narrower, compared to  

the two regions. So in terms of the width, the  Collector region is wider, than the other two  

regions. Because the job of the Collector region  is to collect the electrons, which is supplied by  

the Emitter. And in fact, that is why, it is known  as the Collector. Now depending on the biasing,  

the BJT can be operated in three regions.  The Active Region, the Cut-off Region and  

the Saturation Region. So in case of the Active  Region of operation, the Emitter Base Junction, is  

forward biased. and the Base Collector Junction is  reversed biased. So let's say, the voltage at the  

Emitter is VE, the voltage at the Base is VB, and  the voltage at the Collector is VC. And to forward  

bias this Base Emitter Junction, the voltage  of Base should be greater than the Emitter. And  

similarly, to reverse bias this Collector Base  Junction, the voltage at the Collector should  

be greater than Base. That means, to operate  the BJT, in the active region, we can say that,  

the Collector voltage should be greater than Base  voltage, and the Base voltage should be greater  

than Emitter voltage. So once this condition  is satisfied, then the BJT will operate in the  

active region. Similarly, in the Cut-Off region  both Base-Emitter junction and the Base Collector  

junctions are reversed biased. So to operate the  BJT in this region, the Emitter voltage, should be  

greater than Base voltage, and at the same time,  the Collector voltage should also be greater than  

Base voltage. Similarly, in case of the Saturation  Region of operation, both Base Emitter, and the  

Base Collector junction of the BJTs, are forward  biased. That means in this region of operation,  

the Base voltage VB is greater than Emitter  voltage, and at the same time, this Base voltage,  

is also greater than Collector voltage. So these  are the three regions of operation, in case of  

the BJT. Apart from that, there is a one more  region of operation, which is known as the Reverse  

Active Region of Operation. So in this region of  operation, instead of Base Emitter Junction, here  

the Base Collector Junction is forward biased, and  the Base Emitter Junction is reverse biased. But  

in this region of operation, the gain provided by  the BJTs very less, and due to that, this region  

of operation is usually avoided. Similarly, if we  talk about the PNP transistor, then in case of the  

Active Region of Operation, this Base Emitter  Junction is forward biased, and the Collector  

Base Junction is reverse biased. But in this case,  now the Emitter voltage is greater than the Base  

voltage, and similarly the Base voltage is greater  than Collector voltage. So we can say that,  

in case of the PNP transistor, to operate it in  the active region, the Emitter voltage should be  

greater than Base voltage, and the Base voltage  should be greater than the Collector voltage.  

And similarly, this PNP transistor can also  be used in the different regions. So whenever,  

the BJT is used for the amplification, then it  is used in this Active Region. And whenever it is  

used as a switch, and it is used in the Saturation  in the Cut-off Region. And in the upcoming videos,  

we will see in detail about these different  regions of operation. Now if we talk about  

the symbol, then this is the symbol of the  NPN transistor. So these three terminals,  

are the Base Collector and the Emitter. And here,  this arrow indicates the direction of the current  

during the Active Region of Operation. So in case  of the NPN transistor, the current will flow from  

the Base towards the Emitter. On the other end,  if you see the symbol of the PNP transistor, then 

it is similar to the NPN transistor, but here the  direction of the arrow will get reversed. So now,  

the current will flow from the Emitter  towards the Base region. Now as I said,  

when the BJT is used for the amplification of the  signal, then it is operated in the active region.  

And there are different ways to configure it.  So in case of the common Emitter configuration,  

the Emitter terminal is common between the input  and the output. That means, in this configuration,  

the input signal is applied between the Base and  the Emitter, and the output is measured, between  

the Collector and the Emitter terminal. Similarly  in case of the common Collector configuration,  

the Collector terminal is common between the  input and the output side. And likewise in the  

common Base configuration, the Base terminal is  common between the input and the output side.  

So each configuration has its own advantage  and disadvantage, and we will see all these  

configurations in detail in the upcoming videos.  But in short, depending on the requirement,  

and the application, the BJT can be configured in  any of these three configurations. All right,  

so now let's understand the working of the BJT,  whenever it is operated in the active region.  

And here, we will take the example of the NPN  transistor. Now before we understand the working,  

let me just clear the notations, which is used for  the supply voltages. So as you can see were here,  

for the Base and the Collector supplies,  double subscription is used. That means here,  

this VBB is a source voltage for the Base. And  the VCC is the source voltage which is connected  

to the Collector terminal. And this voltage VBE  defines the difference between the voltage at the  

Base and the Emitter terminal. So this voltage VBE  can be defined as voltage VB minus VE. So if the  

voltage at the Base terminal is let say VB and  the voltage at the Emitter terminal is VE, then  

the voltage VBE can be defined as voltage VB minus  VE. And here, this voltage VB and VE are measured  

with respect to the ground terminal. Similarly,  this voltage VCE can be defined as the Collector  

voltage VC minus VE. So instead of VBE if we write  voltage VEB, then it can be written as voltage VE  

minus VB. And this voltage, will be negative of  the VBE. So throughout our discussion on the BJT,  

we will use these notations. So here these Base  voltage, and the Collector voltage, is applied  

in such a way that, the base Emitter Junction  will get forward biased. And the Base Collector  

Junction will get reversed bias. That means  over here, the BJT is biased in such a way that,  

this voltage VBE is positive, and this voltage  VCB is also positive. Now if you notice over here,  

this is the PN Junction. So whenever this PN  Junction is forward bias, and the typical photo  

voltage drop across this diode is in the range of  0.6 to 0.7 volt. That means, whenever we forward  

bias these Base Emitter Junction, then the typical  voltage drop between these Base and the Emitter  

Junction, will be roughly around 0.7 volt. Now  once we apply this biasing voltages, and the  

electrons from the Emitter, will be pushed towards  the Base terminal. Because as I said earlier,  

the Emitter is the heavily doped. That means  the Emitter has the large number of electrons,  

as the majority carriers. And once we apply the  biasing voltage, then this negative voltage will  

push the electrons towards the Base region. So due  to that, the electrons will starts moving towards  

the Base region. Now once the electrons enters  this Base region, and there are two paths for  

them. One is they can flow towards the positive  terminal on the left, and the second is they can  

flow into the Collector region. But most of the  electrons will enter into the Collector region.  

Because if you see over here, the Base is lightly  doped. That means a number of holes in this Base  

region, is very small compared to the electrons,  which are coming from the Emitter region. That  

means the free electrons, which has come into this  Base region will see the longer lifetime. And the  

second reason is, the width of this Base region is  very thin. That means most of the electrons, will  

be able to escape this Base region, and they can  go into the Collector region. That means in this  

Base region, only few electrons will recombine  with these holes, and they will be get attracted  

towards the positive terminal of this VBB. And the  remaining electrons will enter into the Collector  

region. Now, if you notice over here, once the  electrons from the Emitter enter into the Base  

region, then they will become the minority  charge carriers. And if you see over here,  

the Base Collector Junction is reversed biased. So  due to the applied electric field at the Collector  

terminals these minority charge carriers, or  the electrons will get attracted towards the  

Collector terminal. So once the electrons enters  into this Collector region, then they will get  

attracted by the positive terminal of this VCC. So  if you see the direction of the flow of electron,  

and from the emitter the electrons will flow in  this direction, and most of the electrons which  

is emitted by the Emitter will get collected by  the Collector region. And very small amount of  

electrons only will flow in this direction.  And if we see the direction of the holes,  

then it will be exactly opposite to the flow of  electrons. And in fact, the conventional current,  

will also flow in the same direction. That means,  the Base current IB will flow in this direction,  

while the Collector and the Emitter current will  flow in this direction. So now let us establish  

the relationship between all these currents. So  if you apply the KCL, then we can say that this  

current IB plus IC, that is equal to Emitter  current. That means the Emitter current is the  

summation of this Base current and the Collector  current. As I said, only fraction of electrons,  

are able to go in this direction. That means the  Base current will be very small. Or we can say  

that, this Collector current IC, is approximately  equal to IE. And exactly it can be defined as  

Collector current IC is equal to alpha times  IE. And this alpha defines, what fraction of the  

Emitter current is flowing through the Collector  terminal. Now if we put this value of IC in this  

expression, then we can say that, this Base current  IB plus alpha times IE is equal to IE. That means  

the Base current IB is equal to 1 minus alpha  times Emitter current. And once again if we put  

the value of IE in terms of the Collector current,  then we can say that, the base current IB is equal  

to 1 minus alpha times IC divided by alpha. That  means the Base current IB is equal to 1 minus  

alpha divided by alpha times Collector current.  Or we can say that, the collector current IC is  

equal to alpha divided by 1 minus alpha times Base  current. And let's say this is equal to beta. That  

means the Collector current IC is equal to beta  times IB. So this beta is known as the current  

gain of the BJT. And typically, the value of  beta varies from 50 to 400 for the different  

transistors. So from this we can say that, IB  plus IC that is equal to Emitter current. That  

means Base current IB plus beta times IB is  equal to IE. That means the Emitter current  

IE can be given as beta plus 1 times IB. So this  is the relationship between the Base current, Emitter current  

and the Collector current. Now if you notice over  here, in this common Emitter configuration, this  

Base current is the current on the input side,  while the Collector current is the current on the  

output side. And these two currents, are related  by this expression. That means by controlling this  

Base current on the input side, it is possible to  control the collector current. And that is why,  

these Bipolar Junction Transistors are known as  the current control device. That means just by  

controlling the input current on the Base side,  it is possible to control the output current.  

On the other end, if you see the other type of  transistor, that is the field effect transistor  

it is the voltage control device. That means  in that case, by controlling the input voltage,  

it is possible to control the output current. Also  if you notice over here, in this configuration of  

the BJT, the output collector current gets  amplified by the factor of beta. And if we  

connect the resistor between the Collector and the  Emitter terminal, then it is possible to amplify  

the input signal. That means after biasing by BJT,  in this configuration, if we apply the AC signal  

at the input, then it is possible to amplify  that signal. And we will discuss about it in  

the detail in the upcoming videos. Now during our  discussion, we haven't considered the current due  

to the minority charge carriers in this collector  region. Because if you notice over here, this Base  

collector Junction is reversed bias. So for a  moment, if we remove this Emitter connection,  

then the current which is flowing through the  Collector is only due to the minority charge  

carriers. And let's say, this current is equal to  IC O. So this current is similar to the reverse  

saturation current, which we have seen in the PN  junction diode. So the total Collector current  

ICT will be equal to the IC plus ICO. Where  this ICO is the current due to the minority  

charge carriers. And typically this current is in  the range of microamperes. While this Collector  

current IC is in the range of milliampere.  So this is all about the different types of  

currents in the BJT. So in the upcoming videos, we  will see the different configurations of the BJT,  

as well as the input and output characteristics of  the BJT. And we will also see, how the BJT can be  

biased using the different techniques. But I hope  in this video, you got a brief overview about the  

BJT. So if you have any question or suggestion, do  let me know here in the comment section below. If  

you like this video hit the like button, and  subscribe the channel for more such videos.