FACULTY OF ENGINEERING LAB SHEET

Transcription

1 FACULTY OF ENGINEERING LAB SHEET CIRCUITS AND SIGNALS EEL 286 TRIMESTER (26/27) -Circuit analysis using ORCAD PSpice

2 Experiment : Circuit analysis using ORCAD Pspice PRECAUTIONARY STEPS:. Read this experiment sheet thoroughly and carefully before coming to your lab session. 2. Take precautions for safety. Also handle equipment carefully to prevent any damages. 3. Try to get as much of the analysis done during the lab session. 4. Close all running programs other than the OrCAD-PSpice program. 5. Seek the approval of your results for each part of the experiment from your lab supervisor before moving to the next one. 6. The lab report should include the graphs, calculations of the resistance values of Part 4., comments and analysis of the findings. 7. Appendix A on page 5 provides some guidelines and examples on how to solve Part 4... Objectives: (i) (ii) (iii) (iv) (v) (vi) To understand the concept of electronic circuit simulation using a software like OrCAD-Pspice To design passive and active low pass filter circuits for various orders. To apply the simulation conditions for passive and active low pass filter circuits for AC sweep analysis. To analyze the simulation results for passive and active low pass filter circuits. To evaluate the performances of active Butterworth and Chebyshev low pass filter circuits from the simulation results To prepare report from the simulation results of the design of active Butterworth and Chebyshev low pass filter circuits 2. Introduction: Methods of circuit analysis vary widely depending on the complexity of the problem. Whereas some circuits require nothing more complicated than the writing of a single equation for their solution, others may require several equations to be solved simultaneously. When the response of a circuit is to be performed over a wide range of frequencies, the work is often both tedious and time consuming. In many cases, the problem to be solved requires that the students have an understanding of which basic laws and principles are involved in the solution. In some cases, if the topology of a network is known, along with complete descriptions of the circuit elements, computer programs can be used to perform the analysis. Such programs have been under development for several decades. Dr.Spice and OrCAD- PSpice are among the powerful programs that are capable of solving many types of electrical networks under a variety of conditions. 2/7

3 3. Procedure: Start OrCAD-Pspice A/D Click start Programs OrCAD demo Capture CIS demo Part I: Variable Component Sweep Analysis Step : From the menu bar click: File New project Step 2: Put name as Project I select Analog Mixed-signal circuit wizard OK. (For the circuit as in Figure ) out PARAMETERS: Resistance = 2 R Resistance L mh IC = -9mA C 2u, IC = v Figure Step 3: Add these functions to your library: (Analog ; Source ; Special ; Sourcstm & Eval). Step 4: Draw the circuit as shown in Figure : Components needed are as follows: Analog (R-var, L, C) Special (PARAM) Ground (/source). {from the vertical menu} Output (Offpageleft-R). {from the vertical menu <<C } Step 5: Key in values: Key in Resistance as value for R Capacitor 2u double click capacitor key in V into IC block ( V as initial condition) highlight IC click display click Display name and value close sub-window Inductor mh double click inductor key in 9 ma into IC block (-9 ma as initial condition) highlight IC click display click Display name and value close sub-window Change the text Offpageleft-R to Out Step 6: Key in reference Double click PARAMETERS (A new window will be pop up) Click new name Resistance key in 2 into resistance block Highlight resistance block click display click Display name and value close subwindow Step 7: Simulation Click Pspice from menu new simulation profile give any name click create choose Time domain Run to time 2 ms click the box parametric sweep choose global parameter parameter name Resistance start value 2 End value increment 2 click OK Click the small triangular icon to run the simulation Click add trace Icon click Vout 3/7

4 Step 8: Results A simulation result shows the transient response with difference value of resistance R Step 9: OPTIONS Click FFT icon to see the frequency domain picture Change the increment to a small value to see more patterns Part II: Design of Passive Low Pass Filter Step : Open a new project named project 2 for the circuit Figure 2. R L mh Out V Vac C u Figure 2 Step 2: Instruct OrCAD to perform AC Sweep analysis with a frequency sweep variable that is to be varied from Hz to KHz at points. Step 3: Run simulation. Step 4: Click trace click Vout. Step 5: A result of low pass filter is displayed. Part III: Design of st Order Butterworth Low Pass Filter Step : Open a new project named project 3 for the circuit in Figure 3. VCC+ R Vac V V+ + A74-4 V- 5 6 VCC+ out 5Vdc V2 5Vdc VCC- V3 C.u VCC- Figure 3 Step 2: Instruct OrCAD to perform AC Sweep analysis with a frequency sweep variable that is to be varied from 5 Hz to 5 KHz at points. Step 3: Run simulation. Step 4: Click trace click Vout. Step 5: A result of low pass filter is displayed. *μa74 can be selected from the Eval library. 4/7

5 4. Laboratory Assignment Second order low pass filter Table : Higher order low pass filter parameters. Order stage 2 nd stage RB/RA f RB/RA f Butterworth dB Chebyshev rd stage RB/RA f Note: Normalized cut-off frequency, f = /[2RC desired cut-off frequency] Overall passband gain (db) (i) Design a st, 3 rd and 5 th order Butterworth low pass filter using Table. The cut-off frequency is 2 khz. All calculations must be shown. The schematic of all three filters together with their frequency responses must be attached in the report. (ii) Design a st, 3 rd and 5 th order 2db roll-off Chebyshev low pass filter using Table. The cut-off frequency is 2 khz. All calculations must be shown. The schematic of all three filters together with their frequency responses must be attached in the report. (iii) Analyze the Butterworth and Chebyshev filter responses. Describe the characteristics of each filter. Write your conclusion. Important: Your report must contain:- i. Introduction ii. Results iii. Analysis/discussion iv. Conclusion You are given one week to prepare and submit your lab report to the lab staff. Reports should be handwritten or typed. Neatness and carefulness will be taken into account in the marking of your report and use your own findings and results. You MUST use the FOE lab report cover template. The template can be downloaded at 5/7

6 Please be instructed that plagiarism is an academic offence and if similar reports are found, you should be required to give an explanation for the similarities and no marks will be given for both the original and the copied ones. Late submission of your lab report will not be entertained. This lab report carries 5% of the total course marks. Marks will be deducted for typed copy. Appendix A Guidelines for Part 4.: Higher-order filters may be constructed by cascading a combination of st and 2nd order filter sections (stages). The basic structure of st order and 2 nd order low pass filter sections is shown in Figure A: RA RB Vi Vo V i Vo Figure Aa: st order low pass filter network. Figure Ab: 2 nd order low pass filter network The block diagrams in Figure A2 illustrate the schemes for a higher-order low pass filter. Odd-order filters are obtained by cascading a st order section with one or more 2 nd order sections. For example, a 5 th order low pass filter can be built by cascading a st order section with two 2 nd order sections. st order 2 nd order 3 rd Order Filter st order 2 nd order 2 nd order 5 th Order Filter Figure A2: Block diagram illustrating the higher-order low pass filters The values and parameters in Table can be used to design the required filters in your assignment. Apply the following relationship: f 2RC where, fc, is the given cut-off frequency. f c 6/7

7 Design examples: ) Third order Butterworth filter: To design a third order Butterworth low pass filter with a cut-off frequency of 9.4 khz. Set C =.F for all the calculations. By referring to Table, it is simple to determine that the selected resistance value should be 82 for all st and 2 nd stages of filters. R k 82 2) Fifth order Butterworth filter: To design a fifth order Butterworth low pass filter with a cut-off frequency of 9.4 khz. Set C =.F in all the calculations. By referring to Table, you can determine the suitable resistance values. 3) Third order Chebyshev filter To design a third order Chebyshev low pass filter with a cut-off frequency of 2.4 khz. Set C =.F in all the calculations. The first stage of the resistance value is calculated as follows: R k.322 By referring to Table, you can determine the suitable resistance values. 4) Fifth order Chebyshev filter To design a fifth order Chebyshev low pass filter with a cut-off frequency of 2. khz. Set C =.F in all the calculations. The first stage of the resistance value is calculated as follows: R k.223 By referring to Table, you can determine the suitable resistance values. 7/7