Non Linear Wave Shaping - Clippers

Prior to the Lab session:

1. Study the operation and working principle of Diode under Forward bias and Reverse bias conditions.
2. Study the Classification of clipper circuits and their operation with positive reference, negative reference and zero reference voltages.
3. Study the procedure for conducting the experiment in the lab.

Objectives:

1. To study the various clipper circuits and to plot the output waveforms for a sinusoidal input of given peak amplitude.(Choose f = 1kHz, Vp-p = 10v)
2. To observe the transfer characteristics of all the clipping circuits on CRO.

Apparatus:

1. CRO (Dual Channel 0 to 20 MHz)                  -                       1 No.
2. Signal Generator( 1Hz to 1 MHz)                    -                       1 No.
3. Diode (1N4007)                                             -                       1 No.
4. Resistor (2.2 K)                                           -                       2 No.
5. D.C Power Supply (0 – 30 V  (dual))                -                       1 No.
6. Connecting wires           
7. Bread board        

Theory:

The process where by the form of a sinusoidal signals are going to be altered by transmitting through a non-linear network is called non-linear wave shaping. Non-linear elements (like diodes, transistors) in combination with resistors can function as clipper circuit.

Clipping circuits are used to select transmission of that part of an arbitrary wave form which lies above or below some particular reference voltage level. Clipping circuits are also referred to as Limiters, Amplitude selectors or Slicers.

Clipping circuits are constructed using a combination of resistors, diodes or transistor and reference voltage. Clipping circuits are classified based on the position of diode as

1. Series diode clipper
2. Shunt diode clipper

Procedure:

1. Connect the circuit as shown in the figures given below.
2. In each case, apply 10 VP-P, 1 KHz Sine wave as I/P using a signal generator.
3. Observe the O/P waveform (VO in the circuit) on the CRO and compare it with I/P waveform.
4. Sketch the I/P as well as O/P waveforms and mark the voltage levels.
5. Note the changes in the O/P due to variations in the reference voltage VR = 0V, 2V.. etc.
6. Obtain the transfer characteristics of Clipper circuit, by keeping CRO in X-Y mode.
7. Repeat the above steps for all the clipping circuits.

Precautions:

1. Set the CRO O/P channel in DC mode always.
2. Observe the waveforms simultaneously in two channels by keeping the same reference ground.
3. See that there is no DC component in the I/P.
4. To find transfer characteristics apply input to the X-Channel, O/P to Y-Channel, adjust the dot at the center of the  screen when CRO is in X-Y mode. Both the channels must be in ground, then remove ground and plot the transfer characteristics.

Circuit Diagrams:

Input Signal

Fig. 2.1 Negative clipper with zero reference (Series clipper)

Fig. 2.2 Positive clipper with zero reference (Series clipper)

Fig. 2.3 Negative clipper with zero reference (Shunt clipper)

Fig. 2.4 Positive clipper with zero reference (Shunt clipper)

Fig. 2.5 Positive clipper with positive reference (Series clipper)

Fig. 2.6 Positive clipper with positive reference (Shunt clipper)

Fig. 2.7 Negative clipper with positive reference (Series clipper)

Fig. 2.8 Negative clipper with positive reference (Shunt clipper)

Fig. 2.9 clipping at two independent levels

Observations:

S.No.	Type of Clipper	Reference Voltage	Practicle Clipping Levels	Voltage
1	Series Positive Clipper	0V	V1
			V2
		2V	V1
			V2
2	Series Negative Clipper	0V	V1
			V2
		2V	V1
			V2
3	Shunt Positive Clipper	0V	V1
			V2
		2V	V1
			V2
4	Shunt Negative Clipper	0V	V1
			V2
		2V	V1
			V2
5	Two  level clipper		V1
			V2

Inference:

The different types of clippers circuits are studied and observed the response for various combinations of VR and clipping diodes.

Viva Questions:

1. Define non linear wave shaping?
2. Define clipping circuit?
3. What is piecewise linear mode of a diode?
4. What are the different types of clippers?
5. Which kind of a clipper is called a slicer circuit?
6. What are the disadvantages of the shunt clipper?
7. What are the disadvantages of the series clipper?
8. What is the influence of the practical diode compared to the ideal diode, in the above circuits?
9. If the input voltage magnitude is less than the reference voltages, then how the outputs look like?
10. Instead of sinusoidal wave form as input, if we give other wave forms like triangular or square, then how the clipping action is performed?

Outcomes: 

After finishing this experiment students are able to design different types clipper circuits and observe the input – output waveforms in the CRO.