Showing posts with label Photodiode. Show all posts
Showing posts with label Photodiode. Show all posts

What is PN junction diode | Symbol | Application | VI characteristics

A P-N junction diode is a silicon. The P-N junction diode is the basic element for semiconductor diodes. One of the terminals is doped with p-type879 material and the other with N-type of material. The schematic symbol shown in the figure, P-N junction diode is made up of P-type silicon and N-type silicon semiconductor materials.

P-N junction diode is used in a variety of applications like LASER, solar cell, LED, digital logic design, DC power supply, etc. This article also gives many more application listed below.

Symbol of PN junction diode :

Symbol of PN junction diode

Application of PN junction diode :
  • Light-emitting diode application
  • Laser
  • It can be also used solar cells
  • It used in the detector as well as the demodulator circuit
  • It is used in many circuit or diode-like, a switching diode, Zener diode, PIN photo-diode, varactor diode
  • It is used as switches in digital logic design
  • It can be also used p-n junction photodiodes
  • It can be used as a rectifier in DC power supply
  • It is also used clipping circuit
  • It can be also used computers, radios, radars as wave shaping circuit
V-I characteristics of PN junction diode :
  • When the anode is positive with respect to the cathode, the diode is to be forward biased. From Vs = 0 to total cut-in voltage, the forward diode current is very small. 
  • Cut in voltage is also known as threshold voltage or called turn-on voltage.
  • For a lower power diode, the current in the forward direction increases first exponentially with voltage and then becomes almost linear.
  • When the cathode is positive with respect to the anode, the diode is said to be reverse biased.
  • In the reverse biased condition, a small reverse current called as a leakage current.
  • The leakage current is almost independent of the magnitude of reverse voltage until this voltage reaches breakdown voltage.
  • At this reverse breakdown, the voltage remains almost constant but reverse current becomes quite high limited only by the external circuit resistance.
  • A large reverse breakdown voltage, associated with high reverse current, so power is lost and maybe diode is destroyed.
  • This shows that the reverse breakdown of a power diode must be avoided by operating it below the specific peak reverse repetitive voltage shown in the figure.

VI characteristics of PN junction diode
V-I characteristics of a P-N junction diode

 This article also gives the various types of diode listed below:

Application of PN junction diode

A lower diode is called a signal diode, it is a PN junction device. A high power diode called power diode is also called as a PN junction device but with constructional features somewhat different from a signal diode. The intricacies in constructing power diode arise from the need to make them suitable for high voltage and some high current applications. Let us have a deep insight into the application about the P-N junction diode to know more details about the P-N junction diode.

The PN junction diode some important applications :

  • PN junction diode is used as a more triple, voltage doubler and quadruples in voltage multiplier circuit.
  • They are used as a switch in many electronics circuits.
  • They are used in power supply.
  • This diode can be used by many circuits rectifiers, varactor for voltage-controlled oscillators.
  • While PN junction diode produced light when biased with a current, so it is used in light-emitting diode application.
  • This diode can be also used for another diode called a light amplification stimulation emission of radiation.
  • In power electronics engineering, it can be used in solar cells.
  • It used in the detector as well as the demodulator circuit so it can be used as a detector for the demodulation circuit.
  • In digital electronics, this diode can be used as switches in digital logic design.
  • It can be used in PN junction photodiodes applications.
  • This diode can be used as a rectifier in the DC power supply.
  • While we are using the clipping circuit, this diode can be used to clip the portion of AC.
  • They are used as clamper to change the reference voltage.
  • Zener diode most commonly used in stabilizing circuits.
  • It can be used as a varactor diode for use in the voltage-controlled tunning circuit as may be found in radio and TV receivers.
  • The voltage across the PN junction biased is used to create temperature sensors and reference voltages.
  • This diode can be used as voltage multipliers to increase the output voltage.
  • It can be used as a signal diode in communication circuits.
  • These diodes must be used in various daily life applications like computers, radios, radars as wave shaping circuits.
  • It is used in many circuits or diode-like, a switching diode, Zener diode, PIN photo-diode, varactor diode.
There are many different types of PN junction diode, let here we have to also cover the application of  various diodes:

So guys if you like our post or you think you have to learn a lot from this PN junction diode and their application in detailed please share and comments below. Thanks and stay connected with ecstuff4u.com

Quantum efficiency of photo detector


In photo detector quantum efficiency is defined as the number of electron hall pair generated per incident photon of energy hv and is given as ȵ

ȵ = Number of electron hall pair generated /  number of incident photons

    =   IP / q  /  Pin / hv

 IP = Average photo current
 Pin = Average optical power incident on photo detector

Absorption coefficient of material determines the quantum efficiency. Quantum efficiency ȵ < 1 as all photons incident will not generate e-h pair. It is normally expressed in percentage.

For example,
On an GaAs photo detector 
Number of photon emitted = 6  × 106 
Average e-h pair generated = 5.4 × 106


ȵ  = 5.4 × 106  / 6  × 106 

      = 0.9
      
      = 90%

Cut-off wavelength of photo detector

A cut of the wavelength of any photodetector can be defined as if any particular semiconductor can be absorbed photon over a limited wavelength range. The highest bandwidth is known as cut-off wavelength.

Cut off wavelength is determined by band gap energy Eg of a material.

      Cut of wavelength = hc / Eg  = 1.24 / Eg  

Where,

Eg  = Electron volts (eV) 
A typical value of cut of wavelength for silicon is 1.06 micrometer and germanium is 1.6 micrometer.

For example :

In PIN photo diode  Eg  = 1.43 eV, hc = 1.24 , find cut of wavelength = ?

 Cut of wavelength = hc / Eg  = 1.24 / Eg
                                                
                                               = 1.24 / 1.43
                    
                                                = 0.867 micro meter
                       
                                                = 867 nm

Photo detector

The photodetector is also called an optical receiver. It converts the variation in optical power into a corresponding variation in the electric current. As compare to the optical transmitter the design of optical receiver is more complicated just because the receiver must detect weak, distorted signals and then make decisions on what type of data was sent based on an amplified version of this totally distorted signal.

Photodiodes are one type of photodetector, is capable of converting light into either voltage or current. That depends upon the mode of operation. In photodetector cut off wavelength and quantum efficiency can be defined as λc and ȵ

The requirement of the ideal photodetector 
  • High sensitivity at the operating wavelength 
  • Spectral response: This parameter also describe the efficiency of the photodetector as a function of wavelength.
  • Size: Photodetector size must be small
  • Voltage: It must be work on small voltage 
  • High fidelity: The received signal must be reproduced as it as far as possible
  • Cost: Cost of the photodetector must be less
  • Noise: Minimum noise must be introduced by the detector device
  • Stability: Performance characteristics of photodetector should not change with a change in ambient conditions
Types of photodetector 

Characteristics of avalanche photo diode

Avalanche photodetector construction and also have current-voltage characteristics curve with, depicts avalanche region to shown in the figure.

This allows each of photo-generated carrier to be multiplied by avalanche breakdown. This effect is known as the avalanche break down effect.

Resulting internal gain within the photodiode, which increases the effective responsibility of the device.



Application of Avalanche photo diode

An avalanche photodiode is a semiconductor device. It is a very similar structure to that of PIN or PN photodiode types. These diodes are specially designed to work in the reverse breakdown area. In an avalanche photodiode is basically two terminal namely anode and cathode. It is similar or looks like Schottky photodiode. Avalanche multiplication of the holes and electrons created by photon impact. Here is some application of avalanche photodiode.
  • High-speed laser scanner 
  • Speed gun
  • PET scanner
  • Data communication
  • White noise generators
  • Sources in radio gears
  • Confocal microscopy
  • Fault location
  • Ultrasensitive fluorescence 
  • Particle detection
  • Optical range finding and Optical fiber

Advantages and disadvantages of avalanche photo diode

An avalanche photodiode is a one type of diode. It is specially designed to work in the reverse breakdown region. In an avalanche photodiode is basically two-terminal namely anode and cathode. It is basically PN junction diode that operates in the avalanche break down the region. This article gives information about the advantages and disadvantages of avalanche photodiode to know more details about it.

Advantages of avalanche photodiode :
  • Includes a greater level of sensitivity
  • High performance
  • Fast response time
Disadvantages of avalanche photodiode :
  • The much higher operating voltage required
  • The output is not linear
  • A much higher level of noise
  • Not as widely used due to low reliability
  • Requires high reverse bias for operation 

Avalanche photo diode

What is an avalanche photodiode?

An avalanche photodiode is one kind of semiconductor device specially designed to work in the reverse breakdown region. The symbol, of this diode, is actually same to a Zener diode. The avalanche diode comprises two terminals namely anode and cathode. The symbol is alike to the normal diode but with turn edges of the vertical bar that is shown in the following figure.

Avalanche photodiode basics :

 An avalanche photodiode is a semiconductor device types of a diode, it looks like as PN photodiode or PIN photodiode. An avalanche photodiode specially designed to work in the reverse breakdown region. In an avalanche photodiode is basically two terminal namely anode and cathode. It is similar or looks like Schottky photodiode. Avalanche multiplication of the holes and electrons created by photon impact.

In this diode when a P-N junction diode is applied with high reverse bias break down can occur by two separate mechanisms direct ionization of the lattice atoms devices, it is a Zener break down and also its is high-velocity carriers causing impact ionization of the lattice atoms called avalanche break down. APD uses has its avalanche break down phenomena for its operation. Here this articles also gives the difference between these two types of a diode; PIN photodiode versus avalanche photodiode.
The avalanche photodiode has its internal gain which increases its responsibility. Shows the figure schematic structure of an APD. By virtue of the doping concentration and physical construction of the N-P  junction, The electric field is high enough to cause of impact ionization.

Under normal operating bias, the I-layer is completely depleted. This is known as reach through condition, hence APDs are also known as reach through APD or reverse APDs.

The avalanche action enables the gain of the diode to be too much increased many times and providing a very much greater level of sensitivity.


APD schematic and variation of E - field across the diode


A breakdown voltage of diode :

The avalanche diode breakdown voltage totally depended on the density of doping. When rising the density of doping will reduce the breakdown voltage of the diode.

                          



Avalanche diode modules :

Avalanche photodiode are available as part of modules which apart from the photodiode also contain additional different electronic components. In particular, there can be a current amplifier integrated into the package, which can not only reduces the number of parts required on a circuit board but also it can also improve the noise performance and results in a better combination of bandwidth and responsivity. Some modules have been specially optimized use for an optical fiber communication system and fiber coupled.


Application of avalanche photodiode :
  • It can be used as white noise generators
  • This diode is more protecting the circuit against unwanted voltages
  • This diode is produced RF noise, they are generally used as noise sources in radio gear
  • It can be also used to generate microwave frequency
For detailed information :
This article also gives the various types of diode listed below:

What is photo diode

What does photodiode mean?

 A photodiode is a device that helps in conversion of light electric current. It is a made of semiconductor material and containing a P-N junction and also it is designed to function in revere bias. Reverse bias means that the p - side of the photodiode is connected to the negative terminal of the battery and n - side means is connected to the positive terminal of the battery. It is also sometimes referred as a photodiode detector, photo sensor or light detector. Photodiode technology has been successfully and widely used due to its low-cost rugged structure.

 A photodiode is very sensitive to light so when light or photons fall on the photodiode it easily converts light into electric current. A solar cell is also known as large area photodiode because it converts solar energy or light energy into electric energy. However solar cell works in bright light.

 Photodiode symbol :

 The schematic symbol of a photodiode is given below.  This diode is in order to convert the modulated electrical light back into an electrical signal type, Photodiode is one type of light detector.
Schematic symbol of a photodiode 
Photodiode looks like a light emitting diode. They have two terminal, one is a smaller end and other is a longer end. The longer end of the diode is the anode terminal while smaller end of the diode is cathode terminals. The characteristics of a photodiode are operated in a reverse bias mode.
The main feature of photodiode includes the  following ways :
  • Long life
  • Quick response
  • The linearity of the diode is too much good with respect to incident light 
  • Noise is very low
  • High Gain
  • Low cost
  • Long lifeline
  • Smaller size
  • Low sensitivity to temperature
  • High response speed
  • Small output current
  • Lightweight
  • Output change with respect to temperature change
  • Wide spectral responseApplied reverse voltage  be low
  • It will be always operated in reverse bias condition
Types of photodiode :

 There are different types of photodiode such as :

 There are many numerous types of photodiode available in the market.  They all work on the same basic principle, but working on different types of photodiode work in a slightly different way. A photodiode can be classified based on its construction are as follows given below :
  • PN photodiode - It is the first type of photodiode to be developed but not as widely used as others due to better performance parameters of other types of photodiodes.
  • PIN photodiode - It is one of the most widely used photodiodes, It generally offers lower capacitance and efficiently collects light photons better than PN photodiodes.
  • Avalanche photodiode -  It provides very high gain levels but comes with high noise levels
For detailed information :
Read more >>
Application of Photodiode :
  • An optical fiber communication system
  • Automotive devices
  • Solar cell panels
  • Medical devices
  • Demodulation
  • Camera light meters
  • Street lights
  • Logic circuit
  • Photodetection circuits
  • Character recognition circuit
  • Televisions and remote control in VCRs
  • Measurement of the intensity of light in science and industry
More detailed information 

Working of photo diode

In the photodiode, convert the modulated light back into an electrical signal. As the intensity of an optical signal at the receiver is very low, the detector has to meet high-performance specifications.

The conversion efficiency must be very high at the operating wavelength. The speed of the response must be high enough to ensure that the signal distortion does not occur. It must be possible to operated continuously over a wide range of temperature for many years.

At present, these requirements are met by a reverse biased p-n photodiode. In these devices, the semiconductor material will absorbs a photon of light, which excites an electron from the valence band to the conduction band.

The photogenerated electron leaves behind it a hole, and so each photon generates two change carriers. This increases the material conductivity so-called photo conductivity resulting in an increase in the diode current. 

V-I characteristics of photodiode :

The characteristics of the photodiode are shown in clearly in the following figure. A photodiode is operated in a reverse bias mode. To show in figure photocurrent is nearly independent of reverse bias voltage which is applied. For zero luminance, the photocurrent is almost zero excluding for small dark current to shown in the figure.
V-I characteristics of a photodiode

Application of photo diode

Photo diode generally used to convert the light into current or voltage based on the mode of operation of the device. So photo diode used in various industries. Now you can check the application of photo diode one by one below :

Application of photo diode :
  • Light detector. 
  • Used in demodulates.
  • Encoders.
  • Optical communication system.
  • High speed counting and switching circuits. 
  • Computer punching cards and tapes.
  • Light operated switches.
  • Sound track films.
  • Cameras.
  • Electronic control circuits. 
  • Used in cameras.
  • Medical devices.
  • Digital signal processing.
  • Safety equipment.
  • Position sensors. 
  • Bar code scanners.
  • Automotive devices.
  • Compact disk player.
  • Smoke detector.
  • Position sensor.
  • Surveying equipment.

PIN photo diode

What is the PIN diode?

 The PIN photodiode is a one type photodetector, it is used to convert an optical signal into an electrical signal. A photodiode in general and in this case PIN photodiode will respond to different light wavelength. It is generally the thickness of top p-type region one of the key parameters in determining the response sensitivity.

Basically, the PIN diode is a one types of a photodetector. This diode can be diagrammatical as being a PN junction. but in PIN diode intrinsic layer between the PN and layers. It converts an optical signal into an electrical signal. 

The PIN diode comprises three regions:
  1.  P - region
  2.  I - region
  3.  N-region 
In PIN diode both the P and N region are heavily doped and the region between the P and N layer where there are no majority carriers
Structure of  PIN diode
PIN diode operates in the exact same way as a normal diode. but the only difference is that depletion region, It normally exists between the P and N region in the reversed diode is larger. A region between the P and N region contains no charge carriers.

P and N region are heavily doped, P region has been doped holes and N region has been doped to contain excess electron. so the region between P and N region contain no charge carrier as any electrons or holes combine, so the depletion region has no charge carriers it acts as an insulator.

When the diode is forward biased, the carrier concentration, holes and electron is very much higher than the intrinsic level carrier concentration. 

This article also gives the various types of diode listed below:
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