Engr Circuits and Devices Lab Experiment # 4 -- Operational Amplifiers

Transcription

1 Engr Circuits and Devices Lab Experiment # 4 -- Operational Amplifiers Purpose: To investigate some properties of practical high-gain amplifiers To gain experience in using operational amplifiers in circuit design A. PREPARATION: (To be done individually before coming to the laboratory) Read Alexander and Sadiku s discussion on operational amplifier circuits on pages and review the description of the properties of the 741 op amp given in Lab No. 3 including the input requirements and the pinout diagram. Answer the following questions in your laboratory notebook. 1. What are the electrical characteristics of an ideal operational amplifier? What are the corresponding typical values for the 741 op amp that you will be using in the lab? 2. Design an inverting amplifier with a gain magnitude of exactly 150 and an input resistance of at least 2000 ohms. 3. Draw a circuit diagram that will provide the output V o for the inputs V 1 and V 2 given by: V o = -10V 1-5V 2 4. Design an averaging amplifier with four inputs using a feedback resistor of 10 kω. The circuit 1 should provide the following output: v o = ( v1 + v2 + v3 + v4 ) Draw the circuit diagram of a voltage follower (i.e., no gain). What is its principal use or advantage? 6. Design a circuit that amplifies the difference between two inputs by 2 using (a) only one op amp, and (b) two op amps. 7. Draw a circuit diagram to provide the following output with V o (t) = - 5 t vi ( t) dt Draw the circuit of an op amp differentiator; sketch the output for a triangular-wave input. Experimental Procedure: 1. Inverting Op Amp Amplifier Figure 1 Figure 1 shows an inverting op amp amplifier circuit. a. Using circuit principles, derive the relationship between the output and the input of the inverting op amp amplifier. 1

2 b. Using MultiSIM, plot the output voltage as a function of the dc input voltage. Use the dc sweep option of the analyses tool for input voltage V in = 0.1, 0.2, 0.3, 0.4, 0.5 V. c. Construct the circuit shown in Figure 1. d. Experimentally verify the gain of the amplifier using a tabulation of input voltages and output voltages for dc input values equal to V in = 0.1, 0.2, 0.3, 0.4, 0.5 V, and then to V in = -0.1, -0.2, - 0.3, -0.4, -0.5 V. e. Repeat part (c) and above for sinusoidal inputs of frequency 1kHz. f. Compare results of parts (d) and (e) with theoretical values of the output based on part (b). 2. Non-inverting Op Amp Amplifier Figure 2 Figure 2 displays a non-inverting op amp amplifier circuit. a. Using circuit principles, derive the relationship between the output and the input of the noninverting op amp amplifier. b. Construct the circuit shown in Figure 2. c. Experimentally verify the gain of the amplifier using a tabulation of input voltages and output voltages for dc input values equal to V in = 0.1, 0.2, 0.3, 0.4, 0.5 V, and then to V in = -0.1, -0.2, - 0.3, -0.4, -0.5 V. d. Repeat part (c) above for sinusoidal inputs of frequency 1kHz. e. Compare results of parts (c) and (d) with theoretical values of the output based on part (a). 3. Voltage summing amplifier Figure 3 Figure 3 displays a voltage summing op amp amplifier circuit. a. Using circuit principles, derive the relationship between the output and the input voltages. 2

3 b. Construct the voltage summing op-amp circuit. c. Using dc inputs only, complete the following tabulation: Input Voltages Output Voltage V out V 1 V 2 Measured Calculated d. Compare measured and calculated values of the output. Explain possible sources of error. 4. Voltage difference amplifier Figure 4 Figure 4 shows a voltage difference op amp amplifier circuit. a. Using circuit principles, derive the relationship between the output and the input voltages. b. Using MultiSIM, plot the output voltage as a function of the dc input voltage V 1, with input voltage V 2 set at 2 V. Use the dc sweep option of the MultiSIM s analyses tool for input voltage V 1 from -4 V to 4 V. c. Construct the voltage difference op-amp circuit. d. Using dc inputs only, complete the following tabulation: Input Voltages Output Voltage V out V 1 V 2 Measured Calculated e. Compare measured and calculated values of the output. Explain possible sources of error. f. Design a circuit that will provide the output V o for the inputs V 1 and V 2 given by: 3

4 V o = 2V 1-1V 2 5. Basic integrating op-amp circuit Figure 5 Figure 5 shows a basic integrating op amp circuit. a. Using circuit analysis techniques, derive the relationship between the input and output variables of the circuit. b. Construct the circuit first using a sinusoidal input of frequency 1kHz and amplitude 1V. c. On the same graph, sketch both the input and output voltages, carefully showing the amplitudes and the phase shift between the signals. Write equations for the input and output as functions of time. d. Repeat parts (b) and (c) using a square wave as input. 6. Basic op-amp differentiator Figure 6 shows a basic differentiating op amp circuit. Figure 6 a. Using circuit analysis techniques, derive the relationship between the input and output variables of the circuit. b. Perform a MultiSIM simulation of the circuit for both triangular and sinusoidal inputs. c. Construct the circuit first using a sinusoidal input of frequency 1kHz. 4

5 d. On the same graph, sketch both the input and output voltages, carefully showing the amplitudes and the phase shift between the signals. e. Repeat parts (b) and (c) using a triangle wave as input. 7. Voltage-to-current converter Figure 7 shows a voltage-to-current converter. Figure 7 a. Derive an expression for the current I o in terms of the voltage source V S. b. Construct the circuit with V S = 5 V, R S = R 1 = 1 kω. c. Measure the current I 0 through the load resistor for R L = 220, 270, 470 and 560 Ω. Report Preparation: Prepare a formal lab report following the suggested format. Include MultiSIM simulations for the inverting op amp, difference op-amp and op amp differentiator circuits analyzed in the lab. Attach your answers to the prelab questions as an appendix to your report. Attach a copy the evaluation sheet given on the next page 5

6 Engr 261 Circuits and Devices Lab Report #4 Evaluation Sheet* Name: Due Date: Date Submitted: Note: Lab reports will be prepared and submitted individually. Organization and Structure 1. Introduction Theoretical Background Procedure Results Conclusion Appendices including answers to questions Content Part 1: Inverting Amplifier - Derivation, Experimental Verification & Comparison Part 2: Non-inverting Amplifier Part 3: Summing Amplifier Part 4: Difference Amplifier - Derivation, Verification, Comparison & Design Part 5: Integrating Amplifier Part 6: Differentiator Part 7: Voltage-to-Current Converter MultiSIM Simulations Mechanics 1. Free of grammar, spelling and punctuation errors Appropriate sentence structure ===== ===== ===== ===== Subtotals Grand Total: out of 60. Final Grade: out of 30. *This evaluation sheet should be included in your lab report. 6