Clipper circuits are one of the basic electronic circuits. Every time when we design some circuits, we will have to restrict or slice the input waveform for obtaining desired output. Almost all circuits require this kind of process. From the property of diodes, scientists found out that slicing or restriction of waveforms is possible. For that they used the most important property of diodes, ‘the unidirectional conductivity’ of diodes.Such devices used to shape or slice waveforms are known as clipper circuits. It is also known as a slicer circuit. According to the output port (across which the output is taken), diode clipper circuit is classified into
Select IN4001 or BY 126 diode
- Shunt clipper
- Series clipper
- DC Sources
Circuit Diagram and Working of different Clippers
- Clipping circuits are non-linear wave shaping circuits. They are useful to clip off the positive or negative portions of an input waveform.
- It can also be used to slice off an input waveform between two voltage levels. Using a double clipper we can obtain a moderate quality sine wave. The switching property of diodes is used here.
- In shunt clippers output is taken parallel with the diode and in series clippers output is taken series with the diode. Each of the above mentioned types are discussed below.
Shunt clippers are discussed first.
- A resistance is used to limit the current through the diode.
- The value of the series resistance used is given by the expression R=√ (Rf×Rr) where Rf =forward resistance of diode Rr =reverse resistance of diode.
Different types of shunt clippers are explained below,
Positive clippers at 0V
- This circuit passes only negative going half waves of the input to the output.
- All the positive half cycles are bypassed through the diode to the ground since the diode gets forward biased when the input voltage becomes positive.
- Due to the voltage drop across the diode, clipping occurs at +0.6V.
Negative clipper at 0V
- This passes only positive going half waves of the input to the output.
- All the negative half cycles are bypassed through the diode to the ground since the diode gets forward biased when the input voltage becomes negative.
- Due to the voltage drop across the diode, clipping occurs at -0.6V.
Positive clipper clipping at +3V
- Till the input becomes greater than +3V, diode is reverse biased and the input appears at the output.
- When the input is greater than +3V, diode becomes forward biased and cell voltage appears at the output.
- Due to the voltage drop across the diode, clipping occurs at +3.6V.
Negative clipper clipping at -3V
- When the input voltage becomes less than -3V, diode becomes forward biased and cell voltage appears at the output.
- When the input is greater than -3V, diode is reverse biased and the input appears at the output.
- Due to the voltage drop across the diode, clipping occurs at -3.6V.
- It is a two level clipper. In this clipping occurs at both positive and negative cycles.
- Consider the two level slicer at slicing levels +3V and +5V as shown in figure. Here the input is allowed to go to output between +3V and +5V.
- During the negative cycle of the input, diode D1 conducts and D2 get reverse biased. Output remains at +3V since D1 conducts less than +3V.
- During the positive half cycle, when input exceed +3V, D1 get reverse biased and input appears at output.
- If the input exceed +5V, D2 conducts and the output remains +5V.
- Considering the diode drops, actual clipping occurs at +2.4V and +5.6V.
Theory of series clipper circuit
The Shunt clippers are used to clip the peak of the waveform. Series clippers clip the base level of the signal. Here the diode is connected in series with input. So when diode is ON, input passes to output, otherwise output will be zero.
Design of Clipper circuits
Select IN4001 or BY 126 diode
Current limiting resistance R=√(Rf×Rr)
Typical value Rf= 30Ω Rr=300KΩ