Varactor diode applications

The applications of the varactor diode are mainly used in involve within RF design arena. It mostly used in frequency modulations or tunning circuit where the value of capacitance determines the output modulations frequency. Some of the applications of the varactor diode are listed below:
  • Automatic frequency controller wherein varactor diode is used to set LO signal
  • It is used in a variable resonant tank LC circuit
  • It is used in the electronic application
  • High-frequency radios
  • Frequency modulator
  • RF phase shifter
  • Frequency multiplier
  • It is used radio receiver for tunning the circuit
  • Parametric amplifier
  • Bandpass filters
  • Voltage controlled oscillators
  • Ultra-high-frequency television sets
  • Harmonic generators
  • Frequency control circuits
  • Voltage control oscillator is widely used in receiving and transmitting circuit in the field of communication
  • It can be used in high-frequency areas like Tv tunning and FM radio operations and frequency modulations

Tunnel diode application

Applications of tunnel diode:
  • Tunnel diode can be used as a switch, oscillator, and amplifier
  • It is used as an ultra-high-speed switch
  • It shows a fast response
  • It is used as an ultra 
  • It is used as a high-frequency component
  • Tunnel diode acts as a logic memory storage device
  • It can be used as FM receiver since it is a low current device it is not used more
  • It can be used in modern military equipment
  • It can be used as a microwave oscillator at a frequency of about 10 GHz
  • It is used in nuclear magnetic resource machine
  • It can be used in satellite communication equipment
Practical application of tunnel diode:
  • The tunnel diode is mostly used as a relaxation oscillator circuit
  • It can be used microwave oscillator, which has the frequency above than 10 GHz
  • It can be used as an amplifier
  • It is used as a whenever high switching is needed mostly in control system because it has a switching time of the nanoseconds or picoseconds
  • It is used in satellite communication types of equipment
  • It is used as a memory storage device
  • It is used in nuclear magnetic resource machine
  • It is also used in the military type of equipment like sonars and radars
  • It has a small inductance, capacitance, and also it has negative resistance for that reason it is used in microwave oscillator and relaxation oscillator

tunnel diode definition

The term tunnel diode also called as Esaki diode, this name comes after Leo saki, It was invented in August 1957 by Leo Esaki, Yuriko, and Takashi Suzuki when they were working at Tokyo Tsushin Kogyo. After in 1973 received the Nobel prize in physics for discovering the electron tunneling effect used in these diodes. A tunnel diode is one type of semiconductor diode that has negative resistance due to the quantum mechanical effect called tunneling. The tunnel diode is a highly conductive, heavily doped PN junction diode in which the electric current decreases as the voltage increases. The tunnel diode is a two terminal device with one n-type of semiconductor cathode and other p-type of semiconductor act as an anode. In tunnel diode electric current is caused by the tunneling effect. The tunneling is the phenomenon of conduction in the semiconductor material in which the charge carrier punches the barrier instead of climbing through i

 A tunnel diode is used in high-frequency oscillators, computer, and amplifier. The concentration of the impurity in the normal PN junction diode is about 1 part in 10^8 but in the tunnel diode, the concertation of impurity is about 1 part in 10^3. The diode conducts current both in forward as well as in the reverse direction.
Tunnel diode symbol

Zener diode characteristics

The VI characteristics of Zener diodes shown in the figure given below. This curve shows that when Zener diode if forward bias, it works like a normal diode but when the reverse biased voltage applies across to the Zener diode, the Zener diode breakdown occurs in a different manner.

At Zener breakdown voltage the current stary flowing in the reverse direction, it allows only a small amount of leakage current until the voltage is less than Zener diode
At the certain value of reverse voltage, the reverse current will increase suddenly and sharply. This is an indication that the breakdown has occurred. Breakdown occurs called a Zener breakdown. However, the Zener diode exhibits a controlled breakdown that does damage the device.

This graph shows that Zener breakdown is not exactly vertical shown above which shows that the Zener diode has a resistance. This breakdown voltage of the Zener diode depends on the amount of doped applied. If the diode has heavily doped Zener breakdown occurs at a low reverse voltage, on a different way when the diode is lightly doped breakdown occurs at high reverse voltage. The voltage across Zener is represented by the equation is given below.

V = Vz+IzRz


Zener diode characteristics

What is zener diode

Before we learn about Zener diode first let we understand what is a diode?

The semiconductor diode is a combination of two crystalline semiconductor materials, which designed the two materials know as p-type and n-type. So first let we understand what is n-type and what is p-type of materials

The n-type semiconductor has a larger electron concentration. This is done by introducing a donor as impurities. Here the n-type refers to the negative charge of the electron.

While in p-type of the semiconductor has larger hole concertation, here p-type refers as to the positive charge of the hole.
There are several types of diodes are available for use in electronics design namely a Gunn diode, Laser diode, LED, backward diode, BARITT diode, a PIN diode, PN junction diode, Tunnel diode, Schottky diode, Varactor diode, and Zener diode. Here this article gives the information about what is a diode, what is a Zener diode, different types of Zener diode, application, advantages etc.

What is a Zener diode?

The name of Zener diode was named after American physicist Melvin Zener who discovered the Zener effect. The Zener diode is widely used in all kind of electronic circuit equipment.

The Zener diode is a unique diode which allows the current to flow in one direction like a regular diode but is also permits it to flow in the opposite direction. It allows the flow in the opposite direction when the voltage is above a certain value as Zener voltage. Zener diode consists of a highly doped reversed biased, p-n junction diode while operating in the breakdown region.

In a normal diode, the breakdown voltage is very high and also the diode gets damaged totally if a voltage is above the breakdown diode is applied, but in Zener diodes, the breakdown voltage is not like too much high and does not lead to permanent damage of the Zener diode if the voltage is applied.

A Zener diode is a basically P-N junction type of semiconductor diode, which device designed to operate in the reverse breakdown region.  The Zener diode is always connected in reverse direction because it is specially designed to work in reverse direction. The breakdown voltage of the Zener diode is carefully set by controlling the doping level during manufacture.

The symbolic representation of the Zener diode is given below:
Zenor diode
Zener Diode

Zener diode characteristics of Zener diode:
The VI characteristics of Zener diodes shown in the figure given below. This curve shows that when Zener diode if forward bias, it works like a normal diode but when the reverse biased voltage applies across to the Zener diode, the Zener diode breakdown occurs in a different manner.

At Zener breakdown voltage the current stary flowing in the reverse direction, it allows only a small amount of leakage current until the voltage is less than Zener diode

At the certain value of reverse voltage, the reverse current will increase suddenly and sharply. This is an indication that the breakdown has occurred. Breakdown occurs called a Zener breakdown. However, the Zener diode exhibits a controlled breakdown that does damage the device.
Zener diode characteristics
Zener diode characteristics
For detailed information: >> Read more

 Different types of Zener diodes:
  • Normal diode 
  • Power dissipation
  • Forward voltage
  • Packing voltage
  • Forward drive current
  • Maximum reverse current
For detailed information: >>> Read more

Advantages of Zener diode:
  • High accuracy
  • Small size
  • Power dissipation capacity is very high
  • Low cost
Application of Zener diode:
  • Voltage regulation
  • Voltage reference
  • Switching operation
  • Clamping circuit
  • Various protection circuit
  • Waveform clipper
  • Voltage shifter
  • Voltage stabilizer
  • For meter protection
  • For wave shaping
  • As voltage stabilizer
For detailed information: >>> Read more

 Conclusion:
  • We all know that learn about the above topic we understand that this ordinary diode only that it has been doped to have a sharp breakdown voltage.
  • the diode maintains a stable output voltage irrespective of the input voltage provided the maximum Zener current is not exceeded.
  • The Zener diode default operational state is in the breakdown region that we seen above. It means it actually starts to work when the applied voltage is higher than the Zener voltage is in reversed biased.
  • When Zener diode is forward bias, the Zener diode behaves exactly like the normal silicone diode. It conducts with the same 0.7 V voltage drop that accompanies the use of the normal diode.
  • This diode is mostly used in applications involving, voltage regulations, clipping circuits, and voltage shifters.

Types of Zener diode

There are several types of diodes are available for use in electronics design namely a Gunn diode, Laser diode, LED, backward diode, BARITT diode, a PIN diode, PN junction diode, Tunnel diode, Schottky diode, Varactor diode, and Zener diode. Here this article gives the different types of Zener diode.

Different types of Zener diodes:
  • Normal diode 
  • Power dissipation
  • Forward voltage
  • Packing voltage
  • Forward drive current
  • Maximum reverse current
We have to also explain in details for this diode:
  • Normal diode: The nominal operating voltage of Zener diode is also known as the breakdown voltage of the Zener diode, depending on the application for which type of diode is being to be used, this is often the most important criteria for which Zener diode selection.
  • Maximum Zener current: This refers to the minimum current for the Zener diode start operating in the breakdown region.
  • Power dissipation: This diode represents the maximum amount of power the Zener current can dissipate. Exceeding this power rating leads to an excessive increase in the temperature of the Zener diode which could damage it and also lead to the failure of the things connected to it in a circuit. Thus this factor should be considered when selecting the diode with the user in mind.

Zener diode definition

Definition of Zener diode:

The name of Zener diode was named after the American physicist clearance melvin Zener who discovered the special type of Zener effect. The Zener diode is widely used in all kinds of electronics equipment and mainly used in protecting electronic circuit from overvoltage.

The Zener diode is normal semiconductor type P-N junction diodes operating in reversely biased conditions. The Zener diode is always connected in reverse direction because it is specially designed to work in reverse direction. In other words, the diode which is specially designed for optimizing the breakdown region is known as the Zener diode. The breakdown voltage of the Zener diode is carefully set by controlling the doping level during manufacture.
Zener Diode Symbol
Zener Diode Symbol

Zener diode application

The Zener diode is widely used as a shunt regulator or voltage regulator. When connected in parallel with a variable voltage source so the diodes reverse breakdown voltage. The main application of this type of diodes as a voltage regulator. Over a voltage protector as a voltage reference.
  • The Zener diode is used as voltage reference: In the power supply, a many circuit Zener diode finds as a constant voltage provider or a voltage reference. The only conditions are that the input voltage should be greater than apply Zener voltage and also the series resistor should have a minimum value such that the maximum current flow through the device. 
  • Zener diode as a voltage: In DC circuit Zener diode can be used as a voltage regulator or provide a voltage reference. The main use oZ Zener diode lies in the fact that the voltage Zener diode remains constant for a larger change in current. This makes it possible to use a Zener diode as a constant voltage device or a voltage regulator.
  • Zener diode as a voltage clamper : In a circuit involving AC input source, different from the normal PN diode clamping circuit, a Zener diode can be used The diode can be used to limit the peak of the output voltage to Zener diode at one side and to about 0V at another side of the sinusoidal waveform.

HVAC full form in electrical

What is the full form of HVAC?

  • High Voltage Alternating Current

What does HVAC mean?

An alternating current call as AC is an electrical current that periodically reverses direction in contrast to a direct current that flows in only one direction. These currents typically alternate at higher frequencies than those used in power transmission so HVAC is widely used in the transmission and distribution system to reduce electrical losses.

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What is converter

Definitions:

The use of the word converter in power electronics which is often used as describing several unrelated pieces of equipment or performing a different function has added to this confusing matter, A converter has a lot of meaning but often time you can really understand what it really meant. A converter converts the voltage of an electrical device, usually alternating current (AC) to direct current (DC). It changes the voltage of an electrical power source and it is usually combined with other components to create a power supply. A converter converts AC to DC, detect amplitude modulated radio signals, supply polarized voltage for welding. 

Types:

The basic difference between various types of converters is that they vary in their nature and the devices they support.
  • Analog to digital converter (ADC): This type of converter is a device that converts the input analog voltage to a digital number proportional to the magnitude of the voltage or current form. Some non-electronic or partially electronic device, like rotary encoder, can be considered as ADCs.
  • Digital to analog converter (DAC): It is a device that converts a digital code to an analog signal, DAC are found in CD players, digital music players and PC sound cards.
  • Digital to digital converter (DDC): It is a device which converts one type of digital data to another type of digital data.
Advantages of the converter:
  • Faster dynamic response.
  • Highly reliable.
  • Highly efficient.
  • Negligible maintenance.
  • Very small size.
Disadvantages of a converter:
  • Poor current overload capacity.
  • Low power factor.
  • The good quality automatic regulators are more expensive than other types of mechanical regulators.

Difference between inverter and converter

The converter has a lot of meaning but often times you can really understand what it really meant. For example in electronics, we have understood easily language that the voltage converter is a device that converts AC power to DC power. It changes the voltage of the electrical power source and is usually combined with other components to create a power supply the inverter is defined as an electrical device that converts direct current to alternating current, the converted AC can be at any required voltage and frequency with the use of appropriate transformers switching and control circuits.

The main difference between an inverter and a converter is given below:
  • The inverter is an electrical device that converts the voltage from direct current to alternating current while in Converter is an electrical device that converts the voltage from alternating current to direct current.
  • There are different types of inverters square wave inverters, Quasi-wave, or modified square wave inverters pure sine wave inverters whose converter has three forms analog to digital, digital to analog, and digital to digital form.
  • Inverter is used to convert DC electricity from solar panels, batteries, or fuel cells to AC; micro the inverter for converting DC power from solar panels to AC for the electric grid; UPS uses inverter to supply AC power when mains power is unavailable, induction heating while converter converts AC to DC detect amplitude modulated radio signals, supply polarized voltage for welding.
  • One of the disadvantages of the inverter is that it is not ideal for inductive AC and motor load, sensitive electronic devices can be damaged by poor waveforms by low batteries but in convert has poor current overload capacity, better quality automatic regulators are more expensive than mechanical regulators. 
A key difference between a Converter and an Inverter:
  • Inverters are typically a lot more complex compared to the converters.
  • A converter is used in pretty much all applications while the inverter is used in uninterruptible power supplies.
  • Inverter changes voltage as well as type, A converter changes the voltage but doesn't its type while an inverter changes voltage as well as type.
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Difference between TDMA FDMA CDMA

This page describes FDMA versus TDMA versus CDMA provides a difference between FDMA, TDMA and CDMA technologies. This post also describes multiple access techniques to make use of common resources by multiple users or subscribers.

FDMA:
  • FDMA stands for frequency division multiple access, Here all entire band of frequencies is divided into multiple RF channel. Each carrier is allocated to different users.
  • Segment the frequency band into disjoint subbands.
  • Every terminal has its own frequency uninterrupted.
  • Filtering in the frequency domain.
  • FDMA is simple. established, robust.
  • FDMA is inflexible, frequencies are a scarce resource
  • Cell capacity is limited.
  • FDMA is a hard handoff.
  • Power efficiency reduced.
TDMA:
  • TDMA stands for time division multiple access, here entire bandwidth is shared among different subscribers at fixed predetermined or dynamically assigned time slots.
  • Segments sending time into disjoint time slots demand driven or it would be fixed patterns.
  • All terminal are active for short periods of time of the same frequency.
  • Synchronization in the time domain.
  • TDMA is established fully digital, flexible.
  • TDMA is guard space needed, synchronization difficult.
  • Cell capacity is limited.
  • TDMA is a hard handoff.
  • When we are using TDMA full power efficiency is possible.
CDMA:
  • TDMA stands for time division multiple access, here entire bandwidth is shared among different subscribers at fixed predetermined or dynamically assigned time slots.
  • Spread the using orthogonal codes.
  • All terminals can be active at the same place and also at the same moment uninterrupted.
  • Signal speration for code puls special receivers.
  • CDMA is flexible, less frequency needed soft handover.
  • CDMA is a complex receiver, need more complicated power control for senders.
  • No absolute limit on channel capacity but, it is interference limited for a system.
  • CDMA IS soft handoff.
  • When we are using CDMA full power efficiency is possible.









Difference between half wave rectifier and full wave rectifier

The half wave and full wave rectifier have a significant difference. A rectifier converts AC voltage into pulsating DC  output voltage. A half wave rectifier is an electronic circuit which converts only one half of the AC cycle into pulsating DC output. On the other hand, full wave rectifier is an electronic circuit which converts the entire cycle of AC into pulsating DC output. This page gives the half wave vs full wave rectifier provides the difference between half wave rectifier and full wave rectifier

Half wave rectifier:

  • A rectifier which rectifies only one half of each AC supply. 
  • The frequency of the output signal is exactly the same as that of the input signal.
  • Half wave rectifier gives discontinuous and pulsating DC output, Half wave rectification involves a lot of wastage energy.
  • Half wave rectifier is unidirectional.
  • Half wave rectifier efficiency around 40.6 %.
  • Half wave rectifier is only one diode is required.

Full wave rectifier :

  • A rectifier which rectifies both halves of each AC input cycle is called as full wave rectifier
  • It gives continuous and pulsating output.
  • The frequency of the output signal is double that of the input signal.
  • A full wave rectifier is bi-directional.
  • Half wave rectifier efficiency around 81.2%.
  • Full wave rectifier varies from 2 to 4, in case of a bridge rectifier.

A main key difference between half wave rectifier and Full wave rectifier:

  • Half wave rectifier is a low-efficiency rectifier while the full wave rectifier is high efficiency.
  • The losses due to saturation of the DC core in half wave rectifier and full wave rectifier also create a significant difference. The half wave process DC saturation of core, but this problem can be overcome in the full wave circuit.
  • Full wave requires more electronic components as compared to half wave rectifier. Thus requires double the number of diodes.
  • The ripple factor in case of half wave rectifier is compared to the full wave rectifier, for half-wave rectifier it is about 1.21 but for the full wave rectifier, it is about 0.482.
  • The full wave circuitry does not possess DC saturation of the transformer core because of the current in the secondary winding of the transformer and in opposite directions.
  • A half wave rectifier hs good voltage regulation however full wave rectifier provides better voltage regulation as compared to half wave rectifier.
  • Half wave rectifier does not require centre tapping of the secondary winding of the transformer while full wave rectifier centre tapping of the secondary winding of the transformer.
  • The fundamental ripple frequency in case of half wave rectifier is f, supplied input frequency 50 Hz while in twice the supplied frequency 2f (100Hz) in case of full wave rectifier.
  • The peak inverse voltage in case of half wave rectifier is equivalent to the maximum value of applied input voltage while in peak inverse voltage of full wave rectifier is twice the maximum value of applied input voltage.
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Difference between TDMA and CDMA

TDMA technology was recent in more popular in Europe, Asian countries, Japan, whereas CDMA is widely used in North and South America but nowadays both technologies are very popular throughout the world. TDMA emerged and was utilized first but in CDMA is more recent technology gradually replacing TDMA. The main difference between these two techniques is in the way in which the user shares the same physical channel. This post gives more information about TDMA VS CDMA to better understand this topic.

TDMA:
  • In TDMA all slots are assigned cyclically.
  • Data rate overhead is between 20 to 30 %.
  • Transmission or receiving is allowed for only one user is given slot.
  • The transmission is noncontinuous.
  • All slots are assigned on demand.
  • Due to reduced inter-user interference, power control is less stringent.
  • It is essential to use digital data and also for modulation.
  • Overhead trade-off is the size of data payload and latency.
  • Multiple users are shared with a single carrier frequency.
  • Due to reduced inter-user interference, power control is less transmission.
  • Handoff is made simpler by using the non-continuous transmission.
CDMA:
  • Power limited device.
  • Conversion needs to be extracted from the background.
  • It is difficult to distinguishing individuals when GP is low.
  • Fading would be reduced with a wide frequency spectrum.
  • It needs to have separate multipath signals with different delays by chip unit
  • The system performance will be degraded for every user when the total number of users increases.
  • GP is high when people speak a different language, which is easier to distinguish between individual speakers.
  • CDMA uses a process called the spread spectrum method, which scattering of digital bits in a pseudo-random manner and collecting them for interpretation.
  • While people talking random noise band playing occurs.
  • CDMA allows numerous users to use the channel at the same time while TDMA does not.
A main key difference between TDMA and CDMA:
  • The abbreviation of TDMA is time division multiple access while in CDMA stands for code division multiple access.
  • CDMA is a continuous transmission while TDMA is the discontinuous transmission.
  • TDMA is segmented sending time into disjoint time slot demand-driven or it to be fixed patterns whereas when CDMA has spread the spectrum using orthogonal codes.
  • In TDMA system synchronization in the time domain while in FDMA  signal separation using code puls special receivers.
  • In TDMA all terminal are active for short periods of time on the same frequency while in CDMA can be active at the same place at the same moment uninterrupted.
  • CDMA allows numerous users to use the channel at the same time while TDMA does not allow.
  • CDMA still faces some problems, high complexity, lowered expectations, will be integrated with TDMA or FDMA while in TDMA fixed network together with FDMA or SDMA used in many mobile networks.
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Difference between LCD and LED

The main difference between the LCD and LED is that display LED consumes less power and is the best for picture quality when compared with the LCD  display, This post gives the main key difference between LCD and LED for a better understanding of this topic.

LCD :
  • LCD stands for liquid crystal display.
  • LCD consumes less power. 
  • LCD can be driven directly from IC chips. Driver circuits are not required.
  • LCD has a moderate brightness level.
  • Comparatively less temperature limit. The temperature range is limited to -20 to 60 degrees Celsius.
  • Due to chemical degradation, the lifetime is 50000 hours.
  • The viewing angle for LCD is 100 degrees.
  • The operating voltage range is 3 to 20 VDC.
  • LCD is less expensive than LED. If you want to compromise a bit with the quality you can go for an LCD.
LED:
  • LED stands for a light-emitting diode.
  • LED consumes more power than LCD.
  • Due to the high power requirement, LEDs require an external interface circuit when driven from ICs.
  • The brightness level is very good for LEDs.
  • Lifetime is around 100000 hours.
  • Commercially available LEDs have an operating temperature range of -40 to 85-degree Celsius
  • LED has a wide viewing angle.
  • Operating voltage range 1.5 V to 5 VDC.
  • If you are going to purchase LED, it's more expensive than LCD but has the quality of picture and better features than LCD.

 A key difference between LCD and LED:

Here we will discuss the main difference between LCD and LED, specifically in reference to TVs based on the technology, picture quality, contrast ratio, resolution, viewing angle, etc.

  • LCD stands for liquid crystal display while LED stands for the light-emitting diode.
  • The cost of the LED is more than LCD.
  • The resolution of LED is much better than that of LCD.
  • The LED is a PN junction diode that emits visible when the forward bias applies across it while in LCD uses liquid filaments that are filled between glass electrodes for the emission of light.
  • The direct current reduces the life span of LCD while LED has no effect on it.
  • The switching time of the LED is less than LCD.
  • The LCD uses mercury which pollutes the environment whereas the LED does not use mercury.
  • LED is a faster response time compared to LCD.
  • The display area of the LED is less compared to the LCD.
  • The LED comes with a wider viewing angle than the LCD.
  • LED display gives good quality than LCD.
  • LED provides better colour accuracy than LCD.
  • The LED consumes more power as compared to the LCD.
  • The LED uses gallium arsenides which when heated emit light whereas LCD uses a liquid crystal which is energized and provides light.
  • LCD is not good to create black areas hence not good have contrast as LED while LED has better contrast and black level as it produces better black areas which gives a better quality image.
  • The LCD uses a cold cathode fluorescent lamp which provides the backlight of the screen whereas the LED uses the P-N junction diodes for displaying the light.
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Difference between photodiode and LED

The major difference between the photodiode and LED is that, photodiode work on the principal of the photoconduction while LED operates on the principle of electro-luminance.  This post gives information about photodiode and LED to know more details about the topic.

Photodiode:
  • A photodiode is a light detecting device.
  • A photodiode is a two terminal device which can convert light into electrical energy.
  • Photodiode work on the principle of photoconduction.
  • Photodiode must be used germanium and silicon semiconductor used.
  • It works only reverse bias mode.
  • A photodiode is used in fiber optic communication, fluxmeter up to a couple, etc.
  • Reverse saturation current is significant so dark current flow when no light rays are incident on it.
  • Photodiode must be used switching, high-speed counting, AC coupled signaling, etc.
LED :
  • LED has a light emitting diode.
  • LED is a two terminal device which can convert electrical energy into light energy.
  • LED is work on the principle of electro-luminance.
  • Gallium Arsenide or Gallium phosphide semiconductor used.
  • It works only forward biasing mode.
  • LED generated radiated power due to change in temperature.
  • LED has no leakage current.
  • The LED must be used indicator in AC circuit, Alphanumeric and numeric.
A key difference between photodiode and LED:
  • We all know that photodiode is a light detecting device while LED is a light-emitting diode.
  • LED and photodiode both are two-terminal devices.
  • Photodiode work on reverse biased, LED work on forwarding bias.
  • The major difference is that the photodiode works on the principle of photoconduction while in when we are using LED it to work on the electro-luminance.
  • Photodiode converts light energy into electrical energy and on the other hand LED converts electrical energy into light.
  • A photodiode is made for germanium and silicon semiconductor whereas LED is made for GaAsp or GaP.
  • Photodiode provides energy to electron and holes by exposing itself towards light radiation however LED  emits photons due to electron-hole recombination.
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Difference between photodiode and phototransistor

One major difference between the photodiode and the phototransistor is that photodiode consist of a normal P-N junction diode which a transparent window through which light can fall inside whereas in phototransistor uses a transistor which controls by exposure to light. This article is about photodiode vs phototransistor and also the comparison between the photodiode and phototransistor and also mentions the key the difference between them.

Photodiode:
  • We all know that a photodiode is a P-N junction type of diode and it can generate electric current when light or photon is incident on their surface.
  • A photodiode is only generated current.
  • When we have to use a photodiode output response is too much fast.
  • Sensitivity is less when we have to use a photodiode.
  • A photodiode is working both forward as well as reverse biasing.
  • The photodiode is generating solar power, detecting ultraviolet or infra-rays for measuring light etc.
Phototransistor:
  • The phototransistor is one type of transistor which can convert the light energy into electrical energy.
  • A phototransistor has generated both voltage and current.
  • Output response is slow when we have to use a phototransistor.
  • Sensitivity is more.
  • A phototransistor is only working forward biasing.
  • A phototransistor is used in a smoke detector, compact disc players, an invisible light receiver and LASER etc.
Difference between photodiode and phototransistor :
  • A photodiode is a semiconductor device while phototransistor use as the transistor.
  • Photodiode which can convert the light energy into an electrical current, whereas the phototransistor is for the conversion of light energy into an electrical current.
  • A photodiode is more responsive to incident light than a phototransistor.
  • Photodiode work in both forward as well as reversed bias whereas the phototransistor work in forward biasing.
  • The phototransistor is used as a solid state switch, detecting the light whereas the photodiode is used in solar power plant, in a light meter etc.
  • A phototransistor is more sensitive than a photodiode about one hundred times.
  • Photodiodes pass less current compared to phototransistor while in photodiode consumes less current than a phototransistor.
  • The dark current of the phototransistor is much higher than a photodiode.
  • The photodiode has a linear response over a much wider range of light than a phototransistor.
  • Photodiode produces both voltage and current while phototransistor generates only for current.

Advantages and disadvantages of QPSK

The QPSK stands for Quadrature phase shift keying. We know that the QPSK is a digital technique wherein two binary bits are represented by a change in carrier phase by 90 degrees with respect to the other nearby constellation. This article gives information about the advantages and disadvantages of QPSK to know more details about it.

Advantages of QPSK:
  • QPSK provide very good noise immunity
  • It provides low error probability
  • Bandwidth is twice efficient is compared to BPSK modulation
  • For the same BER, the bandwidth required by QPSK is reduced to half as compared to BPSK
  • It is more efficient utilization of the available bandwidth of the transmission channel
  • Carrier power almost remains constant because of OQPSK amplitude is not much
Disadvantages of QPSK:
  • QPSK is not more power efficient modulation technique compare to other modulation types as more power is required to transmit two bits
  • QPSK is more complex compared to BPSK receiver due to four states needed to recover binary data information
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