EEL2186: Circuit and Signals SIG2


FACULTY OF ENGINEERING

LAB SHEET

CIRCUITS AND SIGNALS

EEL 2186

TRIMESTER 1 (2017/2018)

SIG2-Circuit analysis using ORCAD PSpice

Experiment SIG2: Circuit analysis using ORCADPspice

GENERAL INSTRUCTIONS:
  1. Read this experiment sheet thoroughly and carefully before coming to your lab session.
  2. Try to get as much of the analysis done during the lab session.
  3. Close all running programs other than the OrCAD-PSpice program.
  4. The lab report should include the graphs, calculations of the resistance values of Part 4.0, comments and analysis of the findings.
  5. Appendix A provides some guidelines and examples on how to solve Part 4.0.

1.0Objectives:

(i)To perform simulation of electronic circuits using OrCAD-Pspice.

(ii)To design passive and active low pass filter circuits of various orders.

(iii)To evaluate the performance of active Butterworth and Chebyshev low pass filter circuits from simulation results.

2.0Introduction:

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.

3.0Procedure:

Start OrCAD-Pspice A/D

Click start  Programs  OrCAD demo  Capture CIS demo

Part I: Variable Component Sweep Analysis

Step 1: From the menu bar click: File  New  project

Step 2: Put name as “project 1”  select “Analog Mixed-signal circuit wizard” OK.

Step 3: Add these functions to your library:

(Analog; Source; Special; Sourcstm & Eval) .

Step 4: Draw the circuit as shown in Figure 1.To find the components, go to Place  Part. The components needed are as follows:

  • Analog (R-var, L , C)
  • Special (PARAM)
  • Ground (0/source) {from the vertical menu}
  • Output (Offpageleft-R) {from the vertical menu, Place  Off-page Connector}

To connect the components, Place  Wire.

Step 5: Key in values

  • Key in “Resistance” as value for R1
  • Capacitor “2u”  double click capacitor  key in 10V into IC block (10V as initial condition); you can find this under the Parts tabclick Apply highlight IC  click display  click “Display name and value”  close sub-window.

*In case the program gives error messages when you try to do the above, note that this part is optional:  highlight IC  click display  click “Display name and value”  close sub-window. You may skip them and leave the sub-window open (just minimize it) to avoid the program from crashing. It simply means that the initial conditions will not be explicitly displayed in the schematic diagram.

  • Inductor “10mH”  double click inductor  key in –90mA into IC block (-90mA as initial condition) click Apply  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 “20” into resistance block click Apply  Highlight resistance block  click “display”  click “Display name and value”  close sub-window

Step 7: Simulation

  • Click “Pspice” from menu  new simulation profile  give any name  click “create”  choose “Time domain”  Run to time “2ms”  click the box parametric sweep  choose global parameter  parameter name “Resistance”  start value “20”  End value “100” linear increment of “20”  click OK
  • Click the small triangular icon to run the simulation
  • Click add trace Icon  click Vout. Simulation result shows the transient response with different values 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 1: Open a new project named project 2 for the circuit Figure 2.

Step 2: Instruct OrCAD to perform AC Sweep analysis with a frequency sweep variable that is to be varied logarithmically from 1Hz to 1 kHz at 100 points per decade.

Step 3: Run the simulation.

Step 4: Click trace  click Vout.

Part III: Design of 1st Order Butterworth Low Pass Filter

Step 1: Open a new project named project 3 for the circuit in Figure 3.

Step 2: Instruct OrCAD to perform AC Sweep analysis with a frequency sweep variable that is to be varied logarithmicallyfrom 500Hz to 500 kHz at 1000 points per decade.

Step 3: Run the simulation.

Step 4: Click trace  click Vout.

*μA741 can be selected from the Eval library.

4.0Laboratory Assignment

Table 1: Higher-order low-pass filter parameters.

Order / 1st stage
RB/RA f` / 2nd stage
RB/RA f` / 3rd stage
RB/RA f` / Overall pass-band gain (dB)
Butterworth
3
4
5
6 / - 1
0.1521
- 1
0.068 1 / 1.000 1
1.2351
0.3821
0.586 1 / - -
- -
1.3821
1.482 1 / 6.0
8.2
10.3
12.5
Chebyshev with 2dB ripple
3
4
5
6 / - 0.322
0.924 0.466
- 0.223
0.879 0.321 / 1.608 0.913
1.782 0.946
1.437 0.624
1.637 0.727 / - -
- -
1.862 0.964
1.901 0.976 / 8.3
14.6
16.9
23.2

Note: Normalized cutoff frequency, f` = 1/[2RCfc]

(i)Design 1st, 3rd and 5th order Butterworth low pass filters using Table 1.The cut-off frequency is20 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 1st, 3rd and 5th order 2dB roll-off Chebyshev low pass filters using Table 1. The cut-off frequency is 20 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:-
  • Introduction
  • Results
  • Analysis/discussion
  • Conclusion
  • You are given one week to prepare and submit your lab report to the lab staff.
  • Reports may be handwritten or typewritten. Neatness and carefulness will be taken into account in the marking of your report.
  • You MUST use the FOE lab report cover template. The template can be downloaded at
  • Please be instructed that plagiarism is a serious offence.
  • Late submission of your lab report will not be entertained.
  • This lab report carries 5% of the total course marks.

Appendix A

Guidelines for Part 4.0:

  • Higher-order filters may be constructed by cascading a combination of 1st and 2nd order filter sections (stages). The basic structure of 1st order and 2nd order low pass filter sections is shown in Figure A1:
  • The block diagrams in Figure A2 illustrate the schemes for a higher-order low pass filter. Odd-order filters are obtained by cascading a 1st order section with one or more 2nd order sections. For example, a 5th order low pass filter can be built by cascading a 1st order section with two 2nd order sections.

3rd Order Filter

5th Order Filter

Figure A2: Block diagram illustrating the higher-order low pass filters

  • The values and parameters in Table 1 can be used to design the required filters in your assignment. Apply the following relationship:

where, fc, is the given cut-off frequency.

Design examples:
1) Third order Butterworth filter:

To design a third order Butterworth low pass filter with a cut-off frequency of 19.4 kHz.

Set C = 0.01F for all the calculations.

By referring to Table 1, it is simple to determine that the selected resistance value should be 820 for all 1st and 2nd stages of filters.

2) Fifth order Butterworth filter:

To design a fifth order Butterworth low pass filter with a cut-off frequency of 19.4 kHz.

Set C = 0.01F in all the calculations.

By referring to Table 1, 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 21.4 kHz.

Set C = 0.01F in all the calculations.

The first stage of the resistance value is calculated as follows:

By referring to Table 1, 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 20.1 kHz.

Set C = 0.01F in all the calculations.

The first stage of the resistance value is calculated as follows:

By referring to Table 1, you can determine the suitable resistance values.

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