I - V characteristics of thyristor

The terms thyristor denotes a family of semiconductor devices used for power control in dc and ac system. One of the oldest methods of this thyristor family called silicon control rectifier. An elementary circuit diagram for obtaining static I-V characteristics of a thyristor is shown in the figure.

1. Reverse blocking mode :

• When cathode is made positive with respect to anode with switch S is open. Junction point J1, J3 are seen to bee a reverse biased whereas junction J2 is forward biased.

• A small leakage current of the order of a few mill amperes . This is reverse blocking mode, called the off- state, of the thyristor. In reverse blocking mode to shown in I-V characteristics of thyristor.

• If the reverse voltage is suddenly increased, at a critical breakdown level, called as reverse breakdown voltage VBR, an avalanche occurs at J1 and J3 and the reverse current increase rapidly

2. Forward blocking mode :

• When the anode is positive with respect to the cathode terminal, at that time the gate circuit is to be open and a thyristor is said to be forward-biased as shown in the figure.

• It is seen from this figure J1, J2, J3 are forward biased but J2 is reverse biased.

• As the forward leakage current is small, SCR offers a high impedance. Therefore, a thyristor can be treated as an open switch mode even in the forward blocking mode.

3. Forward conduction mode :

• When anode to cathode forward voltage and it is too much increased with gate circuit open, reverse-biased junction point J2 will have an avalanche breakdown at a voltage called forward break over voltage VB0.

• (This is on-state) after this breakdown occurs, thyristor gets turned on with point shifting to another point and this point anywhere called forward conduction mode.

Difference between GTO and thyristor

Before we learn about the difference between GTO and SCR first let we understand the full meaning of GTO and the full meaning of SCR called thyristor. Here this article gives some following merits and demerits compere between them, so it will very useful for in power electronics applications.

A GTO device has the following disadvantages as compared to a conventional thyristor.

• The magnitude of latching and holding currents is more in a GTO device.
• On state voltage drop and the associated loss is more in the GTO device.
• Due to the multitask cathode structure of GTO, triggering gate current is higher than that required for a conventional SCR device.
• Gate drive circuit losses are too much more.
• Its reverse voltage blocking capability is less than to its forward voltage blocking capability, but this is no disadvantage so far as inverter and chopper circuit is concerned.

In spite of all these demerits, the GTO device has the following advantages over an SCR. 

• GTO device has too much faster-switching speed.
• Its surge current capability is comparable with an SCR device.
• It has more di/dt rating at turn on.
• GTO circuit configuration or design configuration has a lower size and weight as compared to the thyristor circuit unit.
• The GTO unit has higher efficiency because an increase in gate drive power loss and on state loss is more than compensated by the elimination of forced commutation losses.
• GTO unit has reduced acoustical and electromagnetic noise due to the elimination of commutation chokes.

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Application of GTO

GTO is like a conventional thyristor ( CT ) but with added features in it. It can easily be turned off by a negative gate pulse of appropriate amplitude. Nowadays GTO device is now being used in

Application of GTO:

• The high-performance drive system, such as the field-oriented control scheme used in rolling mills, robotics, and machine tools.
• Traction purpose because of their lightweight.
• GTO used in Induction heater.
• Adjustable frequency inverter drive.
• At present, GTOs with rating up 5000 V and 3000 A is available.
• It is used in AC stabilizing power supplies.TO is used in static VAR compensators (SVCs).
• GTO voltage source inverter in a two-terminal HVDC link, which is fed at the sending end by a line-commutated rectifier.
• GTO is used in AC drives.
• GTO is used in DC drives or DC choppers.

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1. GTO vs Thyristor

Difference between Wi-Fi and WiMax

WiMax is similar to the wireless standard known as Wi-Fi, but on a much larger scale and at faster speeds.

A nomadic version would keep WiMax enabled devices connected over large areas much like today's cellphones. This article will explore the various difference between Wi-Fi and WiMax, So now we can compare it with Wi-Fi based on the following factor to details about Wi-Fi and WiMax.

Difference between WiFi and WiMAX :

• Wi-Fi was officially launched in the year of 1997, In WiMax Official release in the year of 2004.
• Wi-Fi stands for "Wireless fidelity" and WiMax stands for "worldwide interoperability for microwave access".
• Wi-Fi is based on format IEEE 802.11 standard, whereas WiMax is based on IEEE 802.16. Both are standards.
• WiMax coverage range up to 30 miles and Wi-Fi coverage range up to is very limited to a small area.
• Wi-Fi provides a few hundred feet with a speed of up to 54 Mbps on the other hand WiMax is provided range up to 40 miles with speeds of 70 Mbps or more.
• Wi-Fi work at 2.7 bps/ Hz and can peak up to 54 Mbps in 20 MHz channel, Whereas WiMax work at 5 bps/Hz and can peak up to 100 Mbps in a 20 MHz channel.
• In the Wi-Fi user scale from one to tens with one subscriber for each consumer premises equipment ( CPE ) device. Fixed channel size 20 MHz, wheres WiMax is designed to efficiently from one to hundreds of consumer premises equipment, with unlimited subscriber behind each CPE. Flexible channel size from 1.5 MHz to 20 MHz.
• In Wi-Fi communication range up to 100 meters, WiMax communication range up to 40 km.
• In WiMax include triple data encryption algorithm and advanced encryption standards, while Wi-Fi, used encryption techniques are advanced encryption standards (AES) and RC4.
• Wi-Fi does not guarantee any QoS but WiMax will provide your several levels of QoS.
• Wi-Fi uses a connection-based or connection-less protocol called CSMA/CA while WiMax uses a MAC protocol that is connection-oriented.
• Most important point is that why we have not used WiMax at home because Wi-Fi is much better speed and technology.
• WiMax offers high-speed internet as broadband access which is transfer voice, video, at very high-speed the same way Wi-Fi offers short-range of data transfer.
• Wi-Fi access point transport signal to the receiving mode the same way WiMax will beam a signal to the receiver.

Thyristor Application

The terms thyristor denotes a family of semiconductor devices used for power control in both DC  and AC system. One of the oldest methods of this thyristor family, called SCR full meaning is silicon control rectifier.

The thyristor is used in many areas of electronics where they find uses in a variety of different applications. 

Application of thyristor :

Transistors are mainly used in electronics applications as voltage and power amplifiers.

Some of the more common applications for them are outlined given below : 

• AC power control (including motors, lights, etc)
• AC power switching.
• AC dimmer. 
• Ideal for switching applications.
• Used in Over voltage protection crowbar for power supplies.
• Control elements in phase angle triggered controllers.
• They are used in photographic flashlights where they act as the switch to discharge a stored voltage through the flash lamp, and then cut it off at the required time.
• They are used in making various gates like AND, NOT etc in digital logic circuits.
• It used in audio and radio frequency amplifiers.
• Used in DC regulators and microprocessors.
• Variable speed motor drives.
• High power inverter and traction.
• Fast heater switching.
• High-temperature oven, glass, ceramics, high-temperature alloys.
• To control variables resistance heater.

What is Thyristor

Meaning of thyristor :

The terms thyristor denotes a family of semiconductor devices used for power control in DC as well as AC system. One of the oldest methods of this thyristor family called silicon control rectifier.

SCR is a four-layer, three junctions, P-N-P-N semiconductor switching device and also have three terminal named: anode (A), a cathode (C) and gate (G).

At present, the use of SCR called thyristor is so vast that over the years, the word thyristor has become synonymous with SCR device. It appears that the terms thyristor is now becoming more common than the actual term of SCR.

The definition of thyristor was decided as under :

Thyristor has constituted three or more p-n junctions. It has two stable states as known as ON state, and OFF state, and it can change its state from one to another.

As per this definition, thyristor now includes a large variety of different semiconductor devices having similar basic characteristics.

Thyristors are used in many applications like light dimmers, motor speed controls, AC power switching, pressure-control systems, and liquid-level regulators.

The silicon controlled rectifier is one of the most popular members of the thyristor family. There are several other members of thyristor family-like PUT, SUS, SCS, Triac, diac etc.

SCS full form

What is the full form of SCS? 

Answer :

• Silicon Control Switch

What does SCS mean?

SCS is a tetrode. It is also called Four Electrode Thyristor. 

It has two gates, one anode gate like a PUT terminal and another cathode gate (KG) like an SCR terminal. You also know the full meaning of SCR.

In other words, SCS is a four-layer, four terminal devices device with anode A, cathode K, anode gate AG and cathode gate KG the own in figure below :

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SUS full form

What is the full form of SUS?

Answer :

• Silicon Unilateral Switch 

What does SUS mean?

A SUS is similar to a PUT  but with an inbuilt low voltage avalanche diode between gate and cathode as shown in the figure. 

Because of the presence of diode, SUS turns on for a fixed anode to cathode voltage, unlike an SCR full form silicon control rectifier whose trigger voltage and/or current vary widely with changes in ambient temperature. 

SUS is used mainly in timing, logic, and trigger circuits. Its rating is about 20 V and 0.5 A. 

Types of thyristor

• The terms thyristor include all four-layer P-N-P-N devices used for control of power in AC and DC systems.
• The silicon controlled rectifier is the most popular member of the thyristor family. There are several other members of the thyristor family-like GTO, ETO, PUT, SUS, SCS, TRIAC, DIAC, etc.

Depending on the turn-off and turn-on capabilities and hence the physical structure, we categorize the thyristor into the following categories :

Major types of Thyristors :

• Silicon controlled thyristor or SCRs
• Bidirectional phase-controlled thyristor or BCTs
• Fast switching thyristor or SCRs
• Bidirectional triode thyristor or BCTs
• Light-activated silicon controlled rectifiers or LASERs
• Reverse conducting thyristor or RCTs
• FET controlled thyristor or FET-CDs
• Gate turn off thyristor or GTOs
• Emitter turn off thyristor or ETOs
• MOS turn off thyristor or MTOs
• Integrated gate commutated thyristors or IGCTs

In recent years, most development effort has gone into both continued integration of the gating and the control electronics into thyristor modules and the use of MOS technology to create gate structures integrated into the thyristor itself.

• Many variations of this theme are being developed and some technologies should rise above in the others in the years to come.

1. PUT :

• PUT full form is Programmable Uni Junction Transistor is a P-N-P-N device like SCR full meaning, but the major difference is that the gate is connected to n-types material near the anode as shown in the figure.
• PUT is used mainly in time delay, logic and also have SCR trigger circuits. Circuit symbol and I-V characteristics of a PUT are shown in the figure.
• In a PUT, Gate is always biased positive with respect to the cathode. When the anode voltage exceeds the gate voltage by about 0.7 V around, Junction j1 point gets forward biased and PUT turn on. When anode voltage becomes less than apply gate voltage, PUT is become turn off.

2. SUS :

• SUS full form Silicon Unilateral Switch is similar to a PUT  but with an inbuilt low voltage avalanche diode between gate and cathode as shown in the figure.
• Because of the presence of diode, SUS turns on for a fixed anode to cathode voltage unlike an SCR whose trigger voltage and/or current vary widely with changes in ambient temperature.
• SUS is used mainly in timing, logic, and trigger circuits. Its rating is about 20 V and 0.5 A. circuit symbol, equivalent circuit and I-V characteristic of a SUS are shown in the figure.

3. SCS :

• SCS full form silicon control switch. For example Four electrons thyristor. It has two gates, one anode gate (AG) like a PUT device and another cathode gate (KG) like an SCR.
• In other words, SCS is a four-layer, four terminal P-N-P-N devices; with anode A, cathode K, anode gate called AG, and cathode gate called KG to shown in the figure.
• SCS can be turned on by either gate. Circuit symbol and also I-V characteristics of an SCS are shown in the figure.
• When a negative pulse is applied to gate anode (AG), junction J1 is forward biased and at that time SCS is turned on.  A positive pulse at AG will reverse bias junction j1 and turn off the SCS.
• A positive pulse at gate kathode  (KG) turns on the device and a negative pulse at KG turns it off. 
• The application includes the timing, logic and triggering circuit, pulse generators, voltage sensors, oscillators.

4. Light-activated thyristors :

• The circuit symbol and I-V characteristics light activated thyristors, are also called LASCR, are shown in the figure. 
• LASCR is turned on by throwing a pulse of light on the silicon wafer of the thyristor. The pulse of the appropriate wavelength is guided by optical fibers to the special sensitive area of the wafer.
• If the intensity of light exceeds a certain value, the excess electron-hole pair is generated due to radiation and forward biased thyristor gets turned on.
• The primary use of light fired thyristor is in high voltage, high current application and also static reactive power compensation etc.
• A light fired thyristor has complete electrical isolation between the light triggering source and the high voltage anode-cathode circuit.
• Light-activated thyristors are available up to 6 kV and also 3.5 kA, with on state voltage drop of about around 2 V and with light triggering requirement of 5mW.

5. Diac ( Bidirectional thyristor diode) :

• Across-sectional view of a DIAC showing all its layers and junction is depicted shown in the figure.
• If voltage V12, with terminal 1 positive with respect to terminal 2, exceeds break over voltage  VB01, then structure P-N-P-N conducts. 
• The term Diac is obtained from capital letters called, DIode that can work on AC. To show in figure Diac has symmetrical breakdown characteristics.
• Its leads are interchangeable. Its turn on voltage is about 30 V.  When conducting, It acts like a low resistance with about 3 V drop across it to shown in figure.
• When not conducting, it acts as an open switch. A DIAC is sometimes called a gate less TRIAC.

6. SCR :

SCR stands for silicon controlled rectifier. It is basically four layered current controlling solid state device. SCRs can conduct current in only one direction, SCR can be triggered normally by the current which is applied to the gate terminal. To know more about SCR follow the link to know more about SCR (thyristor). I-V characteristics of a thyristor

7.Triac :

• SCR full form Silicon Control Rectifier is a unidirectional device that can conduct from anode to cathode only and not from cathode to anode while A Triac can conduct in both the directions. 
• A TRIAC is thus bidirectional thyristor with three terminals MT1, MT2, and Gate. It is used extensively for the control of power in the AC circuit. 
• The word Triac derived by combining the capital letters from the word TRIode and AC. When in operation, a Triac is equivalent to two SCRs connected in anti-parallel. The circuit symbol and its characteristics are shown in the figure.

PUT full form

What is the full form of PUT?

Answer : 

• Programmable Uni Junction Transistor

What does PUT mean?

In a PUT, G is always biased positive with respect to the cathode. When the anode voltage exceeds the gate voltage by near about 0.7 V, Junction gets forward biased and PUT turn on. When anode voltage becomes less than gate voltage, PUT is become turn off. 

It is a PNPN device like SCR, but the major difference is that the gate is connected to n-types material near the anode. 

PUT is used mainly in time delay, logic as well as SCR trigger circuits.

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What is power transistor

Basic information : 

The power transistor is a transistor that used in high power amplifier and power supplies. Power transistors are suited for application where a lot of power is being used current and voltage. It is a junction transistor, is designed to handle high current and power and also used in audio and switching circuits. 

The power transistor is three terminal semiconductor device used to amplify and switch electronic signals and electrical power. They come in NPN, PNP, and Darlington (NPN or PNP) forms.

The structure and construction of a power transistor are entirely different from that of a single transistor but their characteristics and operation are almost the same. 

Power transistors, however, possess controlled characteristics. These are turned on when a current sign is given to base, or control, terminal. The transistor remains in the on-state so long as a control signal is present. When this control signal is removed, a power transistor is totally turned off.

There are four types of power transistor :

• Bipolar junction transistors (BJTs)
• Metal-oxide-semiconductor field-effect transistors (MOSFETs)
• Insulated gate bipolar transistors (IGBTs) 
• Static induction transistors (SITs)

How does a power transistor work? 

A power transistor can mainly do two different jobs such as work as an amplifier or as a switch. When it works as an amplifier, it takes in a tiny electric current at the input and produces a much bigger electric current at the output. 

When it works as switches a tiny electric current flowing through the input of transistor can make a much bigger current flow through the output of transistor. 

Why transistor is used in daily life application?

• High voltage gain
• Require low power supply voltage for operation
• Smaller size 
• No heating problem during operation 
• Solid state device 
• Mechanically so strong
• Easily portable

For detailed information

Read more >>  Power transistor application

Types of FDMA

FDMA is a continuous transmission method. Channel can use one phone circuit at any instant of time. 

Basically, there are two types of  FDMA multiple access methods. 

Types of FDMA : 

• FAMA 
• DAMA

FAMA - FAMA denoted as Fixed assignment multiple access. In FAMA the channel is assigned in a predetermined manner and distributed so that random changes in the capacity are not allowed.

DAMA -  DAMA denoted as Demand assignment multiple access. If there are multiple stations there is a change of capacity and after that, the channel can be allocated to the demand.

FAMA - FDMA :

FDMA deal with link accessing using different frequency band and by multiple stations. It is concerned with the logical link between the stations that are preassigned.

FAMA-FDMA is preassigned. It is not flexible in accordance with the change in traffic.

DAMA - FDMA :

Demand access signifies the allocation of satellite channel to a user on demand, rather than continuously. Therefore demand assignment multiple access is used for earth stations where the traffic conditions are continuously changing.

One demand allocation of channel greatly increases the number of simulations uses who can be served by the system.

For example, telephone voice users communicate at random times, some for less than a minute to voice users communicate at random times, some for less than a minute to several minutes.

If each user were allocated a fixed channel, most of the time the channel will be idle, resulting efficiency utilization of the entire system is low. Therefore demand allocation remarkably increases the number of telephone user served by the system.

Demand access system requires two different types of channel :

• Common signaling channel
• Communication channel

Full form of SCR

What is the full form of SCR?

Answer :

• Silicon Controlled Rectifier OR Semiconductor Controlled Rectifier

What does SCR mean? 

SCR is a four-layer semiconductor current controlling device. It has three terminals called Anode (A), Cathode (C), and Gate (G) and has three junction P-N-P-N.  

The first SCR was developed by a team of power engineers led by Gordon Hall. It was commercialized by Frank W. "Bill" Gutzwiller in 1957. 

It is a unidirectional device, meaning of that it passes electron in only one direction, from the cathode to the anode.

SCR is a General Electric's (GE) trade name for a type of thyristor used for power control in a DC system. SCR is one of the oldest methods of this thyristor family.  

At present, the use of SCR is so vast in recent years that over the years, the word thyristor has become synonymous with SCR. 

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Full form related VLSI

VLSI - Very large scale integrated circuit  

ASIC - Application Specific Integrated Circuit

AVC - Advanced video coding Blu-Ray high-density disc used to store digital information

CABAC - Context-adaptive binary arithmetic coding

CB - Coding block
CLB - Configurable logic block

CIF - Common intermediate format

COE - Co-Efficient file format

CTB - Coding tree block

CTU - Coding tree unit

CU - Coding unit

DVD - Digital video disc

FPGA   Field Programmable gate array

GOP - Group of pictures
GA - Gate array

GPB - Generalized P and B- picture

HDL - Hardware description language

HDTV - High definition television

HEVC - High-efficiency video coding

ISO - International standardization organization
ICS - Integrated circuits   

ITU-T - International telecommunication union – telecommunication standardization sector

JCT-VC - Joint collaborative team on video coding

MPEG - Moving picture experts group

MPM - Most probable modes

MSE - Mean squared error
PLA - Programmable logic array

PB - Prediction block
PSM - Programmable multiplexer

PSNR - Peak signal to noise ratio

PU - Prediction unit

QCIF - Quarter CIF RGB   red green blue (Colour Space)

SAD - Sum of absolute differences
SOG - Sea of gate

TB - Transform block

TU - Transform unit

VHDL - VHSIC hardware description language

VHSIC - Very high speed integrated circuit

YCbCr - Luminance, blue chrominance, red chrominance colour space

YUV - Colour space that stores the luminance and chroma information of a pixel