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?
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:
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.
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.
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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.
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:
- Positive Biased Diode Clipper
- 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.
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.
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:
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.
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:
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.
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
(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.
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