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PN Junction Diode

PN Junction Diode, its Characteristics and Applications

PN junction Diode plays a vital role in our electronic fields, because of their unique property (current flows in only one direction) they are used in many electronic or electrical circuits like rectifiers, switches, clippers, clampers, voltage multipliers.

In this article, we will learn about what is a PN Junction Diode and how it Works and also effect on PN Junction diode with different modes and I am sure this article will help you a lot to understand about Diode.

After completing this article you will be able to:

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  • Understand the PN Junction Diode.
  • Understand the Working of PN Junction Diode.
  • Understand the Effect of Forward Bias and Reverse Bias on PN Junction Diode.
  • Understand the V-I Characteristics of PN Junction Diode.
  • Understand the Practical Applications of PN Junction Diode.

What is PN Junction (Diode):

PN Junction Diode is a two-terminal semiconductor device. It’s made up from a small piece of semiconductor material (usually Silicon), it allows the electric current to flow in one direction while opposes the current in other direction. In the Forward Bias, the diode allows the current to flow in uni-direction. On the other hand, when the diode is reverse biased it opposes the electric current to flow. A PN Junction Diode is a semiconductor device with two opposite region such as (P-type region and N-type region).

  • The P-region is called as the anode and is connected to a positive terminal of a battery and it has Holes in majority carrier and electrons in minority carrier.
  • The N-region is called as the cathode and is connected to the negative terminal of a battery and it has Electrons as a Majority carrier while holes as Minority carrier.

When the P-type semiconductor material is joined with the N-type semiconductor material, a P-N Junction is formed, hence resulting P-N Junction is also called as a P-N Junction Diode.

The basic diode structure and symbol of PN Junction Diode is shown in the figure below.

PN Junction Diode

 
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Biasing of Diode:

Biasing means applying external voltages to the device, biasing of a diode is of two types: Forward Biasing and other one is Reverse Biasing.

Forward Biasing of Diode: We connect positive terminal of the battery to the P-type Material and Negative terminal of the battery to the N-type, hence this configuration is called as Forward Bias Configuration of Diode. In this configuration Diode allows the current to flow in uni-direction.

Reverse Biasing of Diode: We connect Negative Terminal Battery to the P-type Material and Positive terminal of Battery to the N-type Material, hence this configuration is called as Reverse Bias configuration of Diode. In this configuration, diode does not allow the flow of current.

Biasing of PN Junction Diode

For More Read: Biasing of Diode [in Detail]

Forward Bias of Diode:

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Forward bias is the condition that allows current through the PN junction Diode. The voltage source is connected in such a way that it produces a Forward Bias. This external bias voltage is designated as V(bias). The resistor limits the forward current to a value that will not damage the diode.

Note that the -ve side of VBIAS is connected to the n-region of the diode and the +ve side is connected to the p-region. This is one requirement for forward bias.

A second requirement is that the bias voltage, V(bias), must be greater than the barrier potential.

Forward bias of diode

What is Barrier Potential of PN Junction Diode?


A Barrier Potential is an internal potential a semiconductor material, in case of Silicon-based PN Junction diode it is 0.7v and in case of Germanium, it is 0.3v. It means in order to forward bias the PN junction diode V(bias) should be greater than 0.7 for silicon and 0.3V for germanium.


As we know the N-type material is consist of Electrons and the P-type material is consist of Holes.

A fundamental picture of what happens when a PN junction diode is forward-biased is shown below. When the P-type material is connected with a positive terminal of battery it transfers the holes (positive charge carrier), which travels from p-type material to the N-type material through (Junction).

When the N-type material is connected with a negative terminal of battery it transfers the free electrons (negatively charged carriers), which travels from n-type material to the P-type material through (junction).

These free electrons are attracted towards the positive terminal of the diode while the holes are attracted towards the negative terminal of a diode.

Working of diode
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For More Read: Forward Bias of PN Junction [in Detail]

Reverse Bias of Diode:

Reverse bias is the condition that essentially prevents current through the PN junction diode. As mentioned above if we connect -ve terminal of the battery to P-type material and +ve Terminal of Battery to N-type material this lead to the diode in Reverse Bias. note that the depletion region is shown much wider than in forward bias.

A diode connected for reverse bias. A limiting resistor is shown although it is not important in reverse bias because there is essentially no current.

Reverse Bias of PN junction Diode
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An illustration of what happens when a PN junction diode is reverse-biased is shown below. When the P-type material is connected with a negative terminal of a battery, the holes are attracted away from the junction and attracted to the negative electrodes of batter.

Similary when the N-type material is connected with a positive terminal of a battery, the free electrons are attracted away from the junction and attracted towards the positive electrodes.

This results in an increase in the depletion region. As the depletion region widens, the availability of majority carriers decreases. As more of the n- region and p-regions become depleted of majority carriers, the high potential barrier is created thus opposing electric current to flow in reverse bias.

Effect of deplation region on PN junction Diode

Note: if the reverse bias voltage is increased up to a high value, it will damage the PN junction diode.

V-I CHARACTERISTIC OF A PN junction Diode:

As you have learned, forward bias produces the current through a PN junction diode and reverse bias essentially prevents current, except for a negligible reverse current. Reverse bias prevents current as long as the reverse-bias voltage does not exceed the breakdown voltage limit of the junction. Now we will examine the relationship between the voltage and the current in a diode on a graphical basis.

Read More: What is the Duty Cycle?

Effect of Forward Bias on V-I Characteristics of PN Junction Diode:

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When a forward-bias voltage is applied across a diode, there is current. This current is called the forward current.

When the forward-bias voltage is increased to a value where the voltage across the diode reaches approximately 0.7 V (barrier potential), the forward current begins to increase rapidly, as illustrated in Figure given below. As you continue to increase the forward-bias voltage, the current continues to increase very rapidly, but the voltage across the diode is constant till 0.7v for silicon and 0.3v for germinium.

PN junction diode on forward bias

Effect of Reverse Bias on V-I Characteristics of PN Junction Diode

When a reverse bias is applied across a PN junction diode, there is an extremely small reverse current (IR) through the PN junction due to minority carriers.

Once the applied bias voltage is increased to a value where the reverse voltage across the diode reaches the breakdown value of the diode which is (VBR), the reverse current begins to increase rapidly. As you further increase the bias voltage, the voltage across the diode increases above Breakdown, and diode become damaged, thus it’s not a normal mode of operation for most PN junction devices.

PN junction diode on Reverse bias

Complete V-I Characteristics on PN Junction Diode

Characteristics curve of PN junction diode

Combine the curve for both forward bias and reverse bias, and you have the complete V-I characteristic curve for a PN junction diode, as shown in Figure give below.

Applications of PN Junction Diode:


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  1. PN Junction Diodes are mostly used for rectification (Alternative Current to Pulsating DC).
  2. They are used as clipper to clip the portion of AC.
  3. They are used as clamper to change the reference voltage.
  4. They are used as switches in many electronic circuitry.
  5. They are used in Voltage Multipliers to increase the output voltage.
  6. They are used in power supplies.

There are Many different types of PN Junction Diode, and we have covered all of them check out the  working of different types of diodes:

  1. What is a Zener Diode?
  2. What is LED?
  3. What is PhotoDiode? 
  4. What is Tunnel_Diode?
  5. What is Varactor_Diode?

This is all about PN Junction Diode Working, Operations, and its V-I Characteristics if you like our article or you think you have learned from this PN Junction Diode, its V-I Characteristics please share and comment below. Thanks and Stay connected with Studentsheart.com

Difference between diode and zener diode

Difference Between Diode and Zener Diode (Updated)

A major difference between Diode and Zener Diode is that a PN junction diode can operate in forward bias only whereas a Zener Diode can operate in Forward bias as well as in reverse bias. There are a number of differences between a normal diode and a Zener diode and in this article, we will cover them one by one.

We will cover differences between a Diode and Zener diode with respect to their Symbols, Constructions, Operations, and Applications and after reading this article you will be able to understand all major differences between a Diode and Zener diode.

 

Difference between Diode and Zener Diode

Chart down below shows the difference between Diode and Zener Diode.
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PARAMETERDIODEZENER DIODE
Definition Diode is a semiconductor device which allow current in only one direction.Zener diode is special purpose diode which allows current in forward and reverse bias both.
SymbolDiode symbol (2019)Zener diode
OperationDiode is always operated in forward bias it get damages when operated in reverse bias.Zener diode is special diode it can work in forward bias as well as in reverse bias.
DopingDiode is less doped semiconductor device.Zener diode is 1000 times more doped compared to a diode.
ConductivityDiode is uni-directional device (only allow current in one direction).Zener diode is bi-directional device (can allow current in forward and reverse direction).
Breakdown VoltagesDiode has very low breakdown voltage it can not sustain reverse voltages.Zener diode has high breakdown voltages it can sustain large breakdown voltages.
It ObeyDiode obeys Ohm's LawZener diode does not obey Ohm's Law.
ApplicationsDiode is used in rectification, Clipping, Clamping, Voltage Multipliers, Power supplies, Protection Circuits .etc.Zener diode is mostly used in voltage regulators circuits.

 

What is Diode?


A diode is a semiconductor device which is formed when two alternative semiconductors are joined together i.e. when P-layer of Semiconductor and an N-layer of a semiconductor is joined together a junction is formed called a PN junction also called a Diode.

A diode is a current controlling device which is used to control the current in one direction. It is used for applications like Switching, Rectification, Clipper circuits, Clamper circuits, Voltage multipliers, etc.

The P-layer can be considered as a positive layer because it has holes in the majority whereas N-layer is considered as a Negative layer which has electrons in the majority.

Diode symbol (2018)

A diode is similar to a switch it has two modes of operation. When the diode is forward bias it behaves like a closed switch (ON Switch), and when the diode is reverse bias it behaves like an open switch (Off switch).

When the P-type material is connected with a positive terminal of the battery and N-type material is connected with a negative terminal of the battery then the diode is said to be as Forward bias.

When the N-type material is connected with a positive terminal of a battery and P-type material is connected with a negative terminal of battery then the diode is said to be as Reverse Bias.

During forward bias of the diode, the diode does not conduct immediately, but after a unique forward voltage, it starts to conduct. That forward voltage is commonly known as Diode knee voltage. If the diode is made up of silicon material than the knee voltage is 0.7V and if the diode is made up of germanium then the knee voltage is 0.5v.


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Pn junction diode

During reverse bias of diode, the depletion layer starts to widen. Hence a wide depletion region has more resistance for the movement of majority carries thereby electric conductivity is very low. Therefore; no electric current flows in reverse bias of diode.

 

But the minority carriers can flow during reverse bias condition, constituting a very small current in the diode, that small current is temperature dependent. If the reverse bias increase beyond the value of temperature also increases and the minority carriers also increases, which can cause the diode to damage hence reverse bias condition is not used in diode operation.

Therefore, a diode is always operated in the forward bias mode.

What is Zener Diode?


The Zener diode is a special purpose diode which is always operated in the breakdown region. It has the special ability to allow the current to flow in forward direction as well as in the reverse direction, The Zener diode is highly doped as compared to the normal diode.

Zener diode

In terms of the construction, the Zener diode is constructed similar way as a normal diode is constructed; the only difference in terms of their construction is that a diode is less doped as compared to a Zener diode.
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The Zener diode has two modes of operation, When the Zener diode is forward bias It behaves same like a normal diode after the knee voltage of 0.7V it conducts the current in one direction just a like a normal diode, but when the Zener diode is reverse biased, it operates in breakdown region which means it does not get damaged in reverse bias but it works in reverse bias region which makes this diode bidirectional semiconductor device.

zener diode construction

During the reverse bias of the Zener diode, the depletion layer starts to reduce, because a Zener diode is a highly doped diode hence it has very thin depletion region, hence the electric conductivity is high. When the reverse voltage reached at breakdown region the current start to increase in reverse direction and Thus, a Zener diode behaves as a voltage regulator.

Read More: Download any E-Book for Free from Z-Library

Key differences Between Diode and Zener Diode


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  1. Normal diode is operated in forward bias, whereas a Zener diode is a special purpose diode which is operated in forward bias and reverse bias.
  2. In terms of their electric current conductivity, a Diode is a uni-directional device which conducts current in only one direction whereas Zener diode is a bi-directional device which can conduct in forward bias as well as in reverse bias.
  3. In terms of their doping, A normal PN junction diode is less doped as compared to a Zener diode whereas Zener diode is highly doped semiconductor diode.
  4. In terms of their breakdown voltage, A normal diode has very low breakdown voltage it can sustain less amount of reverse voltage, whereas A Zener diode has a very high breakdown voltage which means it can sustain greater reverse voltage compared to the normal diode.
  5. In terms of their operation, A normal diode can operate only in forward bias whereas a Zener diode can operate in reverse bias as well in forward bias.
  6. A normal diode is a primary device and a Zener diode is a secondary device by just applying more doping to a normal diode a Zener diode can be obtained.
  7. A normal diode obeys Ohm’s law whereas a Zener diode does not obey Ohm’s law. Hence, a diode is PTC device whereas Zener diode is NTC device
  8. In terms of their applications, A normal diode is used as rectification operation, clipping operations, voltage multipliers, etc. whereas a Zener diode is used as a voltage regulator.

Conclusion


The Diode and Zener diode are different from each other with respect to their symbols, construction, operations, and applications, a major difference between diode and Zener diode is the electric current conduction normal diode can conduct in one direction whereas Zener diode is able to conduct in both forward and reverse direction.
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Another major difference is that normal diode is less doped whereas Zener diode is a highly doped semiconductor.

A normal diode can get damaged in reverse direction but Zener diode is designed to operate in reverse direction.

A normal diode is used for rectification purpose, clipping, clamping and voltage multiplication operations whereas the Zener diode is commonly used for voltage regulation operations.

Diode Clamper- Positive, Negative Clamper Working and Applications

This article is based on the diode clamper circuit, working of positive and negative clamper circuits and the applications of clamper circuits using different waveforms and circuit.

In our earlier articles, we learn about diodes and the working of diodes and the applications of the diode as half wave rectifier, full wave rectifier, clipper circuits. And in this article, we are moving forward to learn about the clamper circuit and their working.

What is the Diode Clamper?

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A Diode Clamper (DC restorer) is a circuit which changes the dc reference of an ac signal. Basically, a clamping diode circuit(or a clamper) essentially adds a d.c. component of the ac signal.

In Diode Clampers it is important to understand that the shape of the original signal is same it is not changed in the output just the reference of waveform is shifted vertically, this is achieved with clamper circuit.

There are two types of Clamper Diode circuits:

  1. Positive Clamper Circuit
  2. Negative Clamper Circuit

Positive Diode Clamper:

If a vertical shift is achieved in Positive direction i.e. if the signal is pushed up so that the negative peaks falls on the zero level then the clamper is called a positive diode clamper.

Negative Diode Clamper:

The negative Diode clamper does the reverse i.e. it pushes the signal downwards so that the positive peaks fall on the zero level.

The following point is important to understand in Diode Clampers:

The clamping circuit does not change the peak-to-peak or r.m.s. value of the waveform. If you measure the input voltage and clamped output with an a.c. voltmeter, the readings will be the same.

 

Working of Positive Diode Clamper:

To understand the working of positive diode clamper we are applying negative half cycle of the input voltage. When the negative input voltage is applied, the diode is forward biased, allowing the capacitor to charge to almost the peak of the input (Vp(in)-0.7). shown in fig (a).


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Positive clamper During negative cycle

Positive Clamper Circuit Diagram

 

Just after the negative cycle, the diode is reverse bias and capacitor which was charged during the negative cycle that has to now discharge. Which means all the voltage will be summed producing double of Vp(in) at load. Here the amplitude is same just output is clamped. i.e if input Vp was 5v then the clamped output is nearly 10 practically (10-0.7), as shown in fig (b).

Positive Clamper Output

Working of Negative Diode Clamper:


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Reverse the diode and apply positive half cycle first, during positive half cycle of input the diode is forward bias and the capacitor is charging up to (Vp(in)-0.7) after the positive cycle when a negative cycle of input is received the diode is reverse bias which means the charged capacitor has to discharge so the voltage will be summed (vp+vc1) and the summed voltage will appear at output (Load resistor).

Hence such type of clamper is known as Negative Diode Clamper which clamps or pushes the output waveform downwards to the reference.

Negative Clamper Circuit

Negative Clamper Circuit

Negative Clamper Output

Negative Clamper Output

Also Read: Difference Between Clipper and Clamper

Video of Clamper Diode Circuit:

Applications of Diode Clamper Circuit:


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  1. Clampers are mostly used in test equipment, sonar, and radar systems.
  2. They are widely used for their common application of voltage doubles or voltage multipliers.
  3. Clampers are mostly used for removing the distortions
  4. In the transmitting and receiving circuitry of television a clamper is used to stabilize to define sections of the luminance signals to preset levels.
  5. Clampers are used to provide protection to the amplifiers from large errant signals.
  6. They are commonly used for the analysis of synchronized signals from the composite visual signals.

This all about Diode Clamper- Positive, Negative Diode Clamper Working Circuits, If you get the concept and learned something new today then do not forget to leave a comment for us and share our work with your friends’ thanks a lot.

what is diode clipper

Diode Clipper- Positive,Negative,Biased Positive,Combination Biased |EASY|

This article “Diode Clipper- Positive,Negative,Biased Positive,Combination Biased” is based on the Diode clipper circuit, working of positive and negative Diode clipper circuits, biased Positive clipper circuits, Biased Negative clipper circuit combinational biased clipper circuit and the applications of diode clipper circuits using different waveforms and circuit.

What is Diode Clipper?

Diode is a device which allows current to flow in only one direction. For that purpose, we have seen that diodes are used as rectifiers. But diode is not restricted to only this application in this article we will learn about another amazing application of Diode as a Limiters or mostly known as Clippers.

  • A clipper (or limiter) is used to clip off or cut off the portion of applied voltage (A.C) either in Positive direction or Negative direction. Similarly, like Half Wave rectifiers the Clipper circuits clips the positive or negative pulse of a output depending on the circuit configuration.

How to Make Diode Clipper Circuit?


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Clipper circuit can be made by using a simple diode and a resistor. In order to achieve the clipping, an AC signal is applied at the input circuit.

Before starting the operation of clipper circuit you must be clear with basic switching concept of Diode in forward Bias and Reverse Bias.

Basic Concept of Biasing of Diode:

The diode in Forward Bias: In forward bias diode act as a closed switch which means it will pass all the current.

The Diode in Reverse Bias: In Reverse bias diode act as an Open switch which means it will not allow the current to flow.

Quite Clear, let’s move to the Main part.

 

Diode Clipper Circuits:

Clipper circuit is the circuit with which the waveform is shaped by removing a portion of the applied voltage according to the circuits’ configuration.

The important diode clippers are:
(i) Positive Diode Clipper
(ii) Negative Diode Clipper
(iii) Biased Diode Clipper 
(iv) Combination Diode Clipper

Positive Diode Clipper:

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As the name suggests the positive clipper is that which removes the positive half portion of the input voltage, as shown in the picture below. It shows the typical circuit of a positive clipper using a diode here the output  positive half-cycles are removed or clipped off.

Positive Clipper
Working of the Positive Diode Clipper circuit:


The circuit action is simple.
During the positive half-cycle:

  • The diode is forward biased and conducts heavily as defined above. As current always flows in the least resistive path, keeping this in mind when a diode is forward bias it offers the very less resistive path for the current and all the current starts to flow through a diode, the voltage across the RL (Load Resistor) will be ideally Zero and Practically (0.7V) due to barrier potential of Diode,  and due to this reason, output positive half-cycles are clipped off.

During the Negative half-cycle:

  • The diode is reverse biased as it does not conduct as defined above. It will behave as an open switch and offers very high resistance. As we know current always flows in the least resistive path hence all of the current will be passed through RL (Load Resistor) resulting negative cycle is appears at load.

Read More: Download any E-Book for Free from Z-Library

Negative Diode Clipper:

As the name suggests the Negative clipper is that which removes the negative half-cycles of the input voltage, as shown in the picture below. It shows the typical circuit of a negative clipper using a diode here the output voltage has all the negative half-cycles removed or clipped off.

Negative Clipper
Working of the Negative Diode Clipper circuit:

The circuit action is simple and also the opposite of the positive clipper.
During the positive half-cycle:

  • The diode is reverse biased as it does not conduct as defined above. It behaves as an open switch and offers very high resistance. As we know current always flows in the least resistive path, all of the current will be passed through RL (Load Resistor) hence, the positive cycle has appeared at load.

During the Negative half-cycle:

  • The diode is forward biased and conducts heavily. As we know current flows in the least resistive path, all of the current starts to flow through the diode, and the voltage across the RL (Load Resistor) will be ideally Zero and Practically (0.7V) due to barrier potential of Diode. And for this reason, it will clip a Negative cycle.

Read More: What is the Duty Cycle?

BIASED DIODE CLIPPER:


As the name suggests Bias clipper will be consist of bias voltage in series with the diode to its circuit for removing or clipping of small portion of desired half cycle either positive or negative. Given the figure shows the circuit of a biased clipper using a diode with a battery of V volts.

Biased Clippers are of Two Types:

  1. Positive Biased Diode Clipper
  2. Negative Biased Diode Clipper

Positive Biased Diode Clipper:

In a Positive Biased clipper, a Small portion of positive half-cycle will be removed, the negative half-cycles will appear as such across the load. This type of clipper is called biased positive clipper.

Bias Clipper

Working of the Positive Biased Diode Clipper Circuit:

The circuit action is very simple just focus here.

when the input voltage is greater than the biased voltage VBias the output will be equal to Vbias across the RL(Load Resistor) all the greater input voltage will be clipped because when the input voltage exceeds the bias voltage the diode is behaving short and the amount of current is passing through the diode only bias voltage is appearing in the positive cycle. And in the Negative cycle, the diode remains reverse biased. And all of the voltage appears at the load resistor.
For Example:
If the input voltage is 5v and the bias voltage is 2v.
Now here input voltage is greater than the bias voltage that’s why the waveform in the positive cycle will be up to the 2v and the remaining 3v are clipped off or removed.

Why is it so?

  • Because when the input voltage is less than the bias voltage the bias voltage is making diode in reverse bias and it is blocking all the bias voltage across the diode. As we know load resistor is connected parallel to it, all the blocked voltage is appearing at the RL.
  • But when the input voltage exceeds the limit of bias voltage the diode is going in forward bias and it is becoming short all the current is passing through the resistor and the remaining input voltage is clipped and the bias voltage is appearing only.

Negative Biased Clipper:

In a Negative Biased clipper, a Small portion of negative half-cycle will be removed. The Positive half-cycles will appear as such across the load. This type of clipper is called biased Negative clipper.

Working of the Negative Biased Clipper Circuit:

Negative-Biased Clipper

The circuit action is Simple and also reverses of  the Positive Bias clipper.

Combination Biased Diode Clipper:

As the name suggests it is the combination of Biased Positive Clipper and Biased Negative Clipper. Using combination clipper you can clip some desired portion of the positive cycle and also some desired portion of the negative cycle.

combinational biased clipper

Working with Combinational Biased Diode Clipper Circuit:

The circuit action is simple as follows.

  •  When the input voltage is greater than +V1 in a positive cycle, diode D1 conducts and behave as short while diode D2 remains to reverse biased. Therefore, a voltage equal to bias +V1 appears positively across the load. This output remains at +V1 until input voltage is greater than the bias voltage.
  • On the other hand, during the negative half-cycle, the diode D2 will conduct and behave as short while D1 behave as reverse biased. Therefore, a voltage equals to bias voltage V2 appears negatively −V2 across the load. The output remains at –V2 as long as the input voltage in the negative cycle is greater than −V2.

Note that +V1 and −V2 are less than +Vm and − Vm respectively. Between +V1 and −V2 neither diode is on. Therefore, in this condition, It is interesting to note that this clipping circuit can give square wave output.

Example of Combination Biased Clipper circuit:
combination biased clipper example 1

combination biased clipper

combinational biased clipper example 2

the output waveform of combination biased clipper

Summary of All types of Diode Clipper Circuits

Positive Diode Clipper, Clips the positive half of the cycle. A negative diode Clipper,Clips the Negative half of the cycle Whereas a Positive Biased diode Clipper is consist of Diode and bias voltage which is used to clip the desire positive part of positive cycle of input, and the same way Negative biased diode clipper is consist of diode and a Bias voltage but they are configured in exect opposite of the positive diode clipper, A  Negative biased clipper is used to clip desire negative cycle of input, and at last combinational Biased Diode clipper is used to clip desire amount of  both positive and negative input cycle.
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Summary of diode clipper circuit

Summary of diode clipper circuit

More Read: Difference Between Clipper and Clamper With Comparision Chart

Applications of Diode Clippers:

There are various applications of Clippers. Just like they are used in the digital system, radar systems, and other electronic system but here I will tell you the important applications of clipper were they are frequently used.
(i) Changing the shape of a waveform
(ii) Circuit transient protection
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(i) Changing the shape of waveform: Clippers can change the shape of a waveform. From the previous example, it is quite clear that a clipper can be used to convert a sine wave into a rectangular wave, square wave etc. They can change either the negative or positive alternation or both alternations of an A.C voltage.
(ii) Circuit Transient protection: Transients can cause considerable damage to many types of circuits e.g., a digital circuit. In that case, a clipper diode can be used to prevent block the transient to the circuit.

Note: Transients means sudden jerk of current or voltage for the very short period of time.

More Read:

  1. What is Diode Clamper Circuits and How they Work?
  2. What is Voltage Multipliers, Voltage Doubler, Tripler and Quadruple
  3. What is Zener_Diode – Working and Applications of Zener
  4. What is LED- Working and Applications of LED
  5. What is PhotoDiode? Working and Practical Applications of PhotoDiode
  6. What is Tunnel_Diode – Definition, Working, Characteristics & Applications
  7. What is Varactor_Diode, operations and Practical Applications
  8. A Detailed article on What is PN Junction Diode, Characteristics and Applications.
what is led

What is LED- Working and Applications of Light Emitting Diode

This article is based on the Light Emitting Diode, working and operations of Light Emitting Diode (LED) and the applications of Light Emitting Diode (LED).

In our previous articles we learn about diodes and the working of diodes and the applications of a diode as half wave rectifier, clipper circuit, clamper circuits but this is not the end for the applications of a diode, A diode can do much more. A number of specific types of diodes are manufactured for specific applications. Some of the more common special-purpose diodes will be covered in this series.(i) Zener diode (ii) Light-emitting diode (LED) (iii) Photo-diode (iv) Tunnel diode (v) Varactor diode and (vi) Shockley diode.

What is the Light Emitting Diode (LED)?


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A Light Emitting Diode (LED) is the special purpose diode. It gives visible light when it is forward biased. Light Emitting Diodes (LEDs) are widely used for indication purpose.

Why Are LEDs Special Purpose of Diode?

Light Emitting Diode (LED) are the special type of diode because they are not made from Silicon or Germanium, Basically, they are made from elements like Gallium, Phosphorus, and Arsenic. By varying the quantity of these elements, it can produce a different type of colors.

  • It is possible to produce different colors by varying the wavelengths which result to form colors like red, green, blue, and yellow.

For example, Gallium arsenide based LED will produce a red light.  And if the LED is made with gallium phosphide, it will produce a green light.

Symbol of Light Emitting Diode (LED):


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symbol of LED

Terminals of LED:

working of light emitting diode (LED)

 

Biasing of Light Emitting Diode (LED):

Usually, Diode conducts voltage when it is greater than 0.7V for silicon and 0.3 for Germanium but in case of LEDs. As they are made up of different materials like gallium arsenide and gallium phosphide they conduct when the input voltage is greater than the 1.2V to 3.2V.

Working of Light Emitting Diode (LED):

When the LED is forward-biased:

  • When a light-emitting diode is forward bias then the electrons from the n-type material cross the PN junction and recombine with holes in the p-type material.
  • As free electrons (are in conduction band) and these are at a higher energy level than the holes (in the valence band).
  • When the recombination takes place, the electrons release energy in the form of heat and light (Photons).
  • In materials like gallium arsenide and gallium phosphide, the number of photons of light energy is sufficient to produce quite visible light.

forward bias of Light emitting diode

Advantages of LED

The light-emitting diode (LED) is a very useful light source. LEDs have replaced older lamps in many applications because they have the following advantages:

  1. Low voltage
  2. Longer life (more than 20 years)
  3. Fast response time (on-off switching)

Applications of LEDs:


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You can find LEDs all around our life. They are indoors they are in outdoors, they are used in the following areas and circuits:

They are widely used for indication purpose:

  1. In cars and other vehicles for indication purpose
  2. In data displaying LCDs.
  3. In Traffic lights for sign and signals.
  4. They are used in toys and medical equipment’s.
  5. They are used in decorations
  6. They are used in remote controls and much more.

They are widely used in Seven-segment display.

  1. LEDs are grouped to form 7 segment displays.
  2. 7 segment displays are widely used for counting objects.
  3. They are used for displaying numbers
  4. They are used in digital voltmeters and ammeters
  5. They are used in computers, laptops, and mobile phones.
  6. They are used in calculators.
  7. They are used in cloaks and Timer circuits.
  8. They are used in many areas (CNG PUMPS, HOSPITALS, BANKS, AIRPORTS, ETC).

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