Exp. No #2 OBJECTIVE DIODE CLIPPERS AND CLAMPERS The purpose of the experiment is to design and analyze diode clipping, limiting and clamping circuits. Also to measure the voltage limits of both biased and unbiased clipping circuits and to predict the effect of a dc bias voltage on clamping circuits. EQUIPMENT AND COMPONENTS USED 30 MHz Dual Channel Cathode Ray Oscilloscope 3 MHz Function Generator 0-30 V dc dual regulated power supply 1N4007 Diode 1Z5V6 Zener Diode Resistor 1 kω, ¼W Electrolytic Capacitor 10µF/25V Breadboard, Connecting wires, BNC Cables and Probes THEORY Clippers Clipper circuits are wave shaping circuits that has the ability to clip off a portion of the input signal without distorting the remaining part of the alternating waveform. The half wave rectifier is an example of the simplest form of diode clipper. Depending on the orientation of the diode, the positive or negative region of the input signal is clipped off. There are two general categories of clippers: series and parallel. The series configuration is defined as one where the diode is in series with the load, while the parallel variety has the diode in branch parallel to the load. The limiter sets a limit in amplitude of the signal. Zener diode is used in limiter circuits Clampers FURTHER READING The clamper circuit, clamps a signal to a different dc level. The network consists of a capacitor, a diode and a resistive element, it can also employ an independent dc supply to introduce an additional shift. The magnitude of R and C must be chosen so that the voltage across the capacitor does not discharge significantly during the interval the diode is non-conducting. The total swing of the output is equal to the total swing of input signal. 1. Russell L.Meade and Robert Diffenderfer, Foundations of Electronics: Circuits & Devices Conventional Flow, Cengage learning, 2nd edition, 2007. 2. Marc Thompson, Intuitive Analog Circuit Design, Newnes, 2nd edition, 2013. 3. Paul Horowitz and Winfeld Hill, The Art of Electronics, Cambridge University Press, New York, 2nd edition, 1989. 21
CIRCUIT DIAGRAM Figure 1: Unbiased Series Positive Clipper Figure 2: Unbiased Series Negative Clipper Figure 3: Biased Series Negative Clipper Figure 4: Biased Series Positive Clipper Figure 5: Biased Shunt Positive Clipper Figure 6: Biased Shunt Negative Clipper Figure 7: Double Limiter Figure 8: Zener diode Limiter Figure 9: Unbiased Negative Clamper Figure 10: Biased Positive Clamper 22
PRELAB [Bring your simulation files in laptop for evaluation. If required, attach separate sheets for inference] 1. Design and create a SPICE model of unbiased positive and negative clippers shown in Figure 1 & Figure 2 with input signal of 5V peak sine wave at 1 khz. Observe the input and output simultaneously and transfer curve. Comment on the results. Simulate the circuit with square and triangular waveforms as input. Observe the input and output simultaneously and comment on the results. 2. Design and create a SPICE model of biased series positive and negative clippers using diodes shown in Figure3 & Figure4 with input signal of 5V peak sine wave at 1 khz and assume suitable reference voltage. Observe the output waveforms and transfer curve. 3. Design and create a SPICE model of biased shunt positive and negative clippers using diodes shown in Figure5 & Figure6 with input signal of 5V peak sine wave at 1 khz and assume suitable reference voltage. Observe the output waveforms and transfer curve. 4. Design and create a SPICE model of limiter circuits shown in Figure7 & Figure8 and analyze the waveforms. 5. Design and create a SPICE model of positive and negative clampers using diodes with input signal of 5V peak sine wave at 1 khz and assume suitable reference voltage. Plot the output waveforms and transfer curve. Also vary the load resistance and observe the load limitations. 23
Exp. No.: DIODE CLIPPERS AND CLAMPERS Date: OBJECTIVE OBSERVATION 1. Biased Series Clippers Circuit Diagram Practice Procedure 1. Connect the circuit as shown in Figure 3. 2. Apply sine wave of 10Vp-p, 1 khz from function generator. 3. Observe the input, output waveforms and its transfer characteristics on CRO screen. Repeat the above steps for Figure 4. Volt/div = Time/div = Volt/div = Time/div = Graph 1: Input sine wave Graph 2: Output waveform 24
Graph 3: Transfer Characteristics (XY mode) Volt/div = Time/div = Graph 6: Output waveform for circuit in fig 4. Graph 7: Transfer Characteristics (XY mode) Inference 25
2. Biased Shunt Clippers Circuit Diagram Practice Procedure 1. Connect the circuit as shown in Figure 5. 2. Apply sine wave of 10Vp-p, 1 khz from function generator and 2 V dc from regulated power supply. 3. Observe the input, output waveforms and its transfer characteristics on CRO screen. Repeat the above steps for Figure 6. Volt/div = Time/div = Graph 10: Output waveform for circuit in fig 5. Volt/div = Time/div = Graph 11: Transfer Characteristics (XY mode) Graph 12: Output waveform for circuit in fig 6. Graph 13: Transfer Characteristics (XY mode) 26
Inference 3. Limiters Circuit Diagram Practice Procedure 1. Connect the circuit as shown in Figure 7. 2. Apply sine wave of 20Vp-p, 1 khz from function generator. 3. Observe the input, output waveforms and its transfer characteristics on CRO screen. Repeat the above steps for Figure 8. Volt/div = Time/div = Graph 14: Output waveform for circuit in fig 7. Graph 15: Output waveform for circuit in fig 8. 27
Inference 4. Clampers Circuit Diagram Practice Procedure 1. Connect the circuit as shown in Figure 9. 2. Apply sine wave of 10Vp-p, 1 khz from function generator. 3. Observe the input and output waveforms on CRO screen. Repeat the above steps for figure 10. Apply 5V dc from regulated power supply. Volt/div = Time/div = Volt/div = Time/div = Graph 16: Output waveform for circuit in fig 9. Graph 17: Output waveform for circuit in fig 10. 28
Inference UNDERSTANDING & LEARNING 29
POST LAB QUESTIONS 1. How do clipper waveforms differ from those expected if ideal diodes are used? 2. Discuss how lowering of load resistance RL on the clamper circuit affects the output. RESULTS AND CONCLUSION Prepared by: Name: Reg. No.: Date of Experiment : ASSESSMENT Date of Report Submission: Submission Delay (if any):... Student Task Max. Marks Graded Marks Pre-lab Preparation 20 Inference 10 Signature Results & Conclusion 10 Post-lab / Viva-voce 10 Total 50 30