Applications of NPN transistor

NPN transistor with their function in amplifying currents they have many applications and between PNP and NPN, the only difference is the direction of voltage flow.

Let we check the applications of NPN transistor :

• Mostly used in switching applications.
• Used in applications where there is a need to sink current.
• Used in amplifying circuit applications, such as push-pull amplifier circuits. 
• It is used to amplify weak signals in the Darlington pair circuits. 
• Used in temperature sensors. 
• Used in very high-frequency applications.
• Used in logarithmic converters.

Characteristic of BJT

Before we check the characteristics you should know the BJT full meaning. It is helpful to view the characteristic curves of the transistor in graphical form is very similar to the graphical approach used with diodes. 

Now we can check it out the characteristics of BJT. 

BJT Input characteristics :

• A graph of base current I_B Vs base-emitter voltage V_BE gives input characteristics. 
• Since a transistor's base-emitter junction is like a diode I_B versus V_BE graph resembles a diode curve. 
• When collector-emitter voltage V_CE2 is more than V_CE1, base current, for the same V_BE, decreases as shown in the figure. 

BJT Output characteristics :

• A graph of collector current IC Vs collector-emitter voltage V_CE gives output characteristics.
• For zero base current, for example, I_B = 0, as  V_CE is increased, a small leakage (collector) current exists as shown in the figure.
• As the base current is increased from I_B = 0 to I_B1, I_B2 etc, collector current also rises as shown in Figure.

What is NPN and PNP transistor

What is an NPN transistor?

NPN transistors are three-terminal, a three-layer device that can function as either amplifiers or electronic switches. 

In NPN transistor one p-type material is placed between two n-types materials is known as Negative-Positive-Negative type transistor. 

It amplifies the weak signals to enter into the base and produces strong amplify signals at the collector end. In NPN transistor, the direction of movement of an electron is from the emitter to collector region due to which current constitutes in the transistor. 

What is a PNP transistor? 

PNP transistors also are three-terminal, a three-layer device that opposite to NPN transistor where a positive DC voltage is applied to the emitter.  

In PNP transistor one n-type material is placed between two p-type materials is known as Positive-Negative-Positive type transistor.  

PNP transistor uses a small base current and a negative base voltage to control a much larger emitter-collector current. PNP transistor, the emitter is more positive with respect to the base and also a collector. 

The main difference between these two types of transistors is that the holes are more important carriers for PNP transistors, while electrons are more important carriers for NPN transistors. 

Both NPN and PNP transistor are the same in some way and related to each other but they may have differed from each other too. 

You can also check it out the difference between NPN and PNP transistor

Difference between NPN and PNP transistor

Nowadays, the NPN transistor is the most commonly used of the two types. It can be used for amplification and switching application, NPN has higher electron mobility than PNP. Therefore, NPN bipolar transistor is often more favored compared to PNP transistor. Yet they have significantly different characteristics.

Main Difference :

The main difference between them is in their internal structure and also electrical current flow direction. 

Another main difference between these two types of transistors is that the holes are more important carriers for PNP transistors, while electrons are more important carriers for NPN transistors. 

This is all about the main difference between transistor NPN and PNP which are used to design electrical and electronic circuits and various applications. So now let us check some other significant differences are described with the help of comparison between them.

Difference between NPN and PNP transistor

• NPN called for Negative-Positive-Negative type transistor and PNP called for Positive-Negative-Positive. 
• The one p-region is to sandwiched by two n-region, its called NPN transistor with two p-region sandwiched one n-region, called as PNP transistor.
• Both transistors are composed of different materials.
• NPN transistor is turned ON when the electron enters into the base, and the PNP transistor is turned ON when holes enter into the base.
• The current flows from the collector(C) to the emitter(E) in NPN transistor, while in a PNP transistor, the current flows from the emitter(E) to the collector(C).
• In an NPN transistor majority charge carrier electrons and minority charge carrier holes, while  In a PNP transistor majority charge carrier holes and minority charge carrier electrons.
• In an NPN transistor, the switching time is faster while PNP transistor switching time is to be lower.
• The ground signal of the NPN transistor is low, while high in PNP transistor.
• NPN transistor sources it, and PNP transistor sink current. 
• The emitter-base junction of both the transistor NPN and PNP is connected in a biased forward direction.
• Both the NPN and PNP transistor base junction is connected in reverse bias.
• For low current applications, BJT is preferred while MOSFET is suitable for high power functions. 

Difference between working principle :

• NPN transistor: When the current is increased to the base terminal, transistor switches ON and it performs from the collector terminal to the emitter terminal. When reducing the current to the base, the transistor switches ON and the flow of current is so slow. 
• PNP transistor: When the current exists at the base of the PNP transistor, and then the transistor turns OFF while there is no current flow at the base of the transistor then the transistor is switched ON.

What is analog signal processing

Analog signal processing process the signal which is not digitized. It is a defined signal having continuous value.

Common analog processing elements include capacitors, resistors, inductors, and transistors. Analog values are typically represented as a voltage, electric charge around the component in the electronic device. It includes classical radio, radar, TV, telephone, etc. 

Explore more information:

1. What is a digital signal processing
2. What is an analogue signal
3. What is Digital Signal
4. Application of DSP

Full form of technical terms related to power electronics

Full form of technical terms related to power electronics :

• Full form of UJT
• Full form of MCT
• Full form of BJT
• Full form of MOSFET
• Full form of IGBT
• Full form of GTO 
• Full form of SCR
• Full form of PUT 
• Full form of SUS
• Full form of SCS
• Full form of NSS
• Full form of OSS
• Full form of AUS
• Full form of VLR
• Full form of SITH
• Full form of SMPS
• Full form of HVDC
• Full form of UPS
• Full form of RMS
• Full form of TRIAC

What is BJT

BJT full form is a bipolar junction transistor that uses both electron and hole charge carriers. For their operation, BJT uses two junctions between two semiconductor-type such as n-type and p-type. 

BJTs are manufactured in two types, NPN and PNP, and are available as individual components, or fabricated in integrated circuits, in large numbers. The function of a BJT is to amplify current that can be used as amplifiers or switches. These functions offer a wide range of electronic equipment applications, including computers, TVs, mobile phones, audio amplifiers, industrial control, and radio transmitters. 

Meaning of BJT :

• A bipolar junction transistor is a three layer, two junction NPN or PNP semiconductor device with one p-region sandwiched by two n-region and two p-region sandwiched one n-region. It has three terminal named collector (C), Emitter(E), and base(B). 

Figure of  BJT

• The current flow in the device takes place due to movement both holes and electrons. 
• An emitter is indicated by an arrowhead indicating the direction of emitter current. No arrow is associated with base or collector. 

Schematic diagram symbol of BJT :

NPN                                                  PNP  

Types of  BJTs  :

There are two types of junction transistor :

1. NPN transistor 
2. PNP transistor 

This article gave brief details about NPN and PNP transistor like working principle, advantages and application to better understand this topic.

The working principle of NPN transistor : 

• This circuit is NPN types of BJT transistor shown in the figure there are two types of current flow I_C , I_E is receptively known as collector and emitter current and V_CB , V_EB is collector-base voltage and emitter-base voltage.
• Shown in figure current I_C , I_{E  ,} I_B current going into the transistor is and the sign is taken as positive and if current goes out sign is taken as negative.

 NPN transistor Application:

• Use as an amplifier
• Use as a Darling-tone pair
• Use as a switch

The working principle of PNP transistor :

• In P-N-P junction transistor, emitter current enter through the emitter terminal shown in the figure. 
• When using any BJT device, the junction of emitter-base is forward biased and the junction of the collector-base is in reverse biased.

So conclude that BJT can be operated in the different mode of BJT like cut off, saturated and active mode.

PNP transistor application :

• Used in darling-ton pair circuit
• Used in heavy motors to control current flow
• Used as switch
• Used as a robotic workshop
• Used in the amplifying circuit

Difference between BJT and MOSFET

BJT and MOSFET both transistors are useful for amplification and switching applications. Yet, they have many similarities and also different characteristics. As a result, one or the other may be better suited to specific electronics applications. 

Difference between BJT and MOSFET

• A BJT has a negative temperature coefficient device, so current sharing resistors are necessary during parallel operation of BJT's while in MOSFET has a positive temperature coefficient for resistance makes the parallel operation of MOSFET is easy.
• BJT, with a decrease in resistance at that time rise in temperature, the current increases. This increased current over the same area results in hot spot and breakdown of the BJT because of negative temperature coefficient occurs, the secondary breakdown does occur, Whereas in MOSFET device secondary breakdown does not occur, because it has a positive temperature coefficient. 
• BJT stands for bipolar junction transistor, and MOSFET stands for metal oxide semiconductor field-effect transistor.
• BJT is a bipolar device, MOSFET is a uni-polar power electronics device.
• A BJT has three terminals called an emitter, base, and collector, whereas a MOSFET  also has a three-terminal called the gate, source, and drain. 
• BJT current a controlled device while MOSFET is a voltage-controlled device.   
• BJT's are used for low current applications, while MOSFETs are used for high power applications.      
• BJT has a low input impedance (a few kilo-ohms), a MOSFET has a high input impedance  (megaohm).  
• In the analog and digital circuits, MOSFET is considered to be more commonly used compare to  BJT now these days. 
• MOSFET's in higher voltage ratings have much more conduction loss.
• BJTs are available with ratings up to 1200 V and  800 A, and MOSFETs are available with ratings upon 500 V and 140 A. 
• BJT depends on the current at the base terminal and the MOSFET depends on the voltage at the oxide-insulated gate electrode. 
• MOSFET structure is more complex than BJT. 

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1. IGBT vs Thyristor
2. SCR vs TRIAC
3. IGBT vs BJT
4. FET vs MOSFET
5. Thyristor vs MOSFET
6. Thyristor vs Transistor
7. NPN vs PNP Transistor

Full form of SMPS

What is the full form of SMPS?

Answer :

• Switched-Mode Power Supply / Switching Mode Power Supply 

What does SMPS mean?

SMPS is one type of power supply unit uses a switching regulator to convert electrical power efficiently, mainly used in computers to convert the voltage into an acceptable range of power. It also uses a great power conversation technique to reduce the overall power loss.

Explore more information:

1. Full form of SITH
2. Full form of HVDC
3. Full form of HVAC
4. Full form of RMS
5. Full form of UPS
6. Full form of CPT
7. Full form of ATS

IGBT construction

Before knowing about the construction of IGBT one question you should be clear about is  What is full form of IGBT?

IGBT Structure :

Illustrates the basic structure of an IGBT.  IGBT is constructed virtually in the same way as a power MOSFET construct. There a major difference in the substrate. The n⁺ layer subtract at the drain in a MOSFET is now substituted in the IGBT by a p⁺ layer substrate called collector C. Like a power  MOSFET, an IGBT has also thousands of structure cells connected appropriately on a single chip of silicon.
                      

In the IGBT p+ substratum injects holes into n-layer so-called as injection layer. The n-layer is called the region of drift. As in other semiconductor devices, the n-layer thickness determines IGBT's capacity to block voltage. Layer p is called the IGBT body region. the n^- layer between p+ and p regions accommodates the pn^- junction of the depletion layer, Example- junction J_2.

IGBT switching characteristics

How IGBT Switching characteristic works?

Switching characteristics of an IGBT during turn-on and turn-off are sketched in fig. Turn-on time is defined as the time between the instant of forward blocking to forward on the state. Turn-on time is composed of delay time t_dn and rise time ton =  t_dn +t_r.

• The delay time is defined as the time for the collector-emitter voltage to fall from V_CE to 0.9 V_CE. Here V_CE is the initial collector emitter voltage.
• Time t_dn may also be defined as the time for the collector current to rise from its initial leakage current I_CE to 0.1 I_c. Here I_c is the final value of collector. The rise time t_r is the time during which collector-emitter voltage falls from  V_CE.
• It is also defined as the time for the collector current to rise from 0.1 I_C to its final value I_C. After time t_on, the collector current  I_C is and the collector-emitter voltage fall to a small value called conduction drop is said to be V_CES where subscript S denotes saturated value.

• The turn-off time is somewhat complex.
• It consists of three intervals : (i) delay time , (ii) initial fall time and (iii) final fall time.
• t_off = t_df +t_f1+t_f2.
• The delay time is the time during which gate voltage fall forms V_GE to threshold V_GET.
• As V_GE falls to V_GET during t_df, the collector current falls from I_c to 0.9 I_c . At the end of t_df, the collector-emitter voltage begins to rise.
• The first fall time t_f1 is defined as the time during which collector current fall from 90 to 20 % of its initial value of current I_C, or the time during which collector-emitter voltage rise from V_CES to 0.1 V_CE.
• The final fall time t_f2 is the time during which collector current fall from 20 to 10% of  I_c or the time during which collector-emitter voltage rise from 0.1  V_CE to final value  V_CE has shown in  figure.

Applications of power electronics

The era of modern power electronics began with the invention of silicon controlled rectifier by cell bell laboratories in 1956. Its prototype was introduced by GEC in 1957 and subsequently, GEC introduced SCR based systems commercially in 1958.

Since then, There has been the development of many new power semiconductor devices. Today power electronics systems incorporate power semiconductor devices as well as microelectronic integrated circuits.

The terms converter system, in general, is used to denote a static device that converts DC to AC or AC to DC. Conventional power controller based on thyratrons and mercury arc controller using power semiconductor devices in almost all applications. 

The development of new power semiconductor device new circuit topology with their improved performance and their fall in price have opened up a wide field for the new application of power electronic converter. It is said to power semiconductor devices can be regarded as the muscle and the microelectronics as the intelligent brain in the modern power electronic systems.

Some of the typical applications are:

• Domestic and theater lighting.
• Generation and transmission control.
• Power supplies can be used laboratories and uninterruptible power for important loads.
• An industrial application like chemical device, paper, and steel industries.

Some other application of power electronics :

• Aerospace supplies: Space shuttle power supplies, satellite power supplies, aircraft power systems.
• Commercial: Advertising, heating, elevators, light dimmers, uninterruptible power supplies, flashers, and industrial lasers.
• Industrial area: Transformer tap changers, blowers and fans, pumps and compressor, industrial laser, cement mills, rolling mills, textiles mills, cement mills, welding, arc, and industrial furnaces. 
• Residential area: Cooking, vacuum cleaner, lighting, air-conditioning, space heating, refrigerators, electric-door openers, dryers, fans, food warmer trays, personal computers, light dimmer, food mixer, electric blanket.
• Telecommunication device: Power supplies (DC and UPS device), battery chargers.
• Transportation: Electric vehicles, electric locomotives, streetcars, trolley buses, Battery chargers, subways, automotive electronics.
• Utility Process: VAR compensation, HVDC, static circuit breakers, fans, and boiler feed pumps, supplementary energy system.