WAVE SHAPING CIRCUITS USING OPERATIONAL AMPLIFIERS

Transcription

1 WAVE SHAPING CIRCUITS USING OPERATIONAL AMPLIFIERS OBJECTIVE The purpose of the experiment is to design the wave shaping circuits like Clippers, Clampers and Schmitt trigger using op-amps. EQUIPMENT REQUIRED 741 Op-amp Resistors (designed values), ¼ W 0-30 V, 1A dc dual regulated power supply 30 MHz Oscilloscope 3 MHz Function Generator Digital Multimeter Breadboard THEORY Clipper is a circuit that is used to clip off (remove) a certain portion of the input signal to obtain a desired output wave shape. In op-amp clipper circuits, rectifier diode may be used to clip off certain portion of the input signal. In clamper circuits, a predetermined dc level is added to the input voltage. They are also called as dc inserter or restorer. Schmitt trigger is a comparator circuit with hysteresis, implemented by applying positive feedback to the non-inverting input of a comparator. FURTHER READING 1. Ramakand A. Gayakwad, Op-amps and linear integrated circuits, PHI learning, R.M.Marston, Op-amp Circuits Manual, Newnes, Robert Diffenderfer, Electronic Devices: Systems & Applications, Cengage Learning, 2005 CIRCUIT DIAGRAM Figure 1. Active clipper Figure 2. Active Clamper 56

2 Figure 3. Schmitt Trigger with zero reference Figure 4. Schmitt Trigger with positive reference PRACTICE PROCEDURE Active Clipper 1. Construct the circuit as per the diagram shown in Figure1. 2. Apply 2V peak, 1 khz sinusoidal inputs. 3. Observe the input and output waveforms simultaneously. Note the output signal by turning the potentiometer through its entire range. Active Clamper 1. Construct the circuit as per the diagram shown in Figure2. 2. Apply 2V peak, 1 khz sinusoidal input. 3. Vary the potentiometer to apply reference voltage. 4. Observe the input and output waveforms simultaneously. Repeat the above for different values of reference voltages. Report your results. Schmitt Trigger 1. Construct the circuit as per the diagram shown in Figure3. 2. Apply 2V peak, 1 khz sinusoidal input. 3. Observe the input and output waveforms simultaneously. Note the phase of the output with respect to input. Repeat the above for Schmitt trigger with reference voltages as shown in Figure4. Report your results. PRELAB 1. Simulate the circuit of active positive and negative clippers with input signal of 2V peak sine wave at 1 khz and assume suitable reference voltage. Observe the output waveforms. 57

3 2. Simulate the circuit of active positive and negative clampers using 741 op-amps with input signal of 2V peak sine wave at 1 khz and assume suitable reference voltage. Observe the output waveforms. 3. Simulate the circuit of a Schmitt Trigger using 741 op-amps with suitable input signal and threshold voltage. Observe the waveforms for the following conditions (i) Schmitt trigger with zero reference (ii) Schmitt trigger with positive reference. Also note down the upper threshold and lower threshold values. Draw the hysteresis loop. 58

4 Exp. No.: Date: WAVE SHAPING CIRCUITS USING OPERATIONAL AMPLIFIERS OBJECTIVE OBSERVATION Active Clipper Circuit Diagram Waveforms Inference 59

5 Active Clamper Circuit Diagram Waveforms Inference 60

6 Schmitt Trigger Circuit Diagram Waveforms V UT = V LT = 61

7 Inference UNDERSTANDING & LEARNING 62

8 RESULTS AND CONCLUSION Prepared by: Name: Reg. No.: Actual Date of Experiment:. ASSESSMENT Date of Performance:.. Report Submission Date: Submission Delay:... Student Task Max. Marks Graded Marks Pre-lab Preparation 20 Inference 10 Results & Discussion 10 Signature Post-lab / Viva-voce 10 Total 50 63