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Introduction to PSpice

This introduction covers PSpice applications including DC node analysis, sweeps, Bode plots, noise analysis, and more. Learn how to perform basic DC nodal analysis and DC sweep analysis. Understand concepts like Maximum Power Transfer, Kirchoff's Laws, and solve circuits using Cramer's Rule. Get insights on PSpice AC analysis for frequency response and filter design. Explore various filter types, setting up AC analysis, and practical applications in circuit analysis. An essential guide for beginners in PSpice simulations.

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Introduction to PSpice

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  1. Introduction to PSpice Syafeeza Binti Ahmad Radzi Computer Engineering Department FKEKK

  2. Review Multisim – Digital circuit PSpice – Analogue circuit (electric / electronic circuit)

  3. PSpice • Same function as Multisim • Can be used to design - Digital circuit - Analogue circuit - PCB design - IC design • Multisim is used for education purposes while PSpice is widely used in the industry.

  4. What Can You do with PSpice • DC Node Analysis • DC sweeps, component value sweeps • Small signal parameters • Frequency response & Bode Plots • Transient Response • Temperature analysis • Monte Carlo Analysis (for component variations) • Noise Analysis LAB 5

  5. 4.0 DC NODAL ANALYSIS • Every analysis begins with DC Nodecalculation. • Calculate only DC currents and voltages. • Capacitors  open circuits. • Circuit inductors  short circuits.

  6. 4.1 BASIC DC NODAL ANALYSIS

  7. DC NODAL ANALYSIS • Create Netlist: Analysis Create Netlist. • Simulate the circuit: Analysis Simulate. • We will see that the IPROBE and VIEWPOINT parts display the results of the node voltage analysis. • The results of analysis are kept in the output file. • Examine the netlist file: Analysis Examine Netlist. (shows the circuit connection and the number of node) • Examine the output file: Analysis Examine Output. (shows the result of the node voltage analysis)

  8. 4.1 BASIC DC NODAL ANALYSIS VIEWPOINT IPROBE The IPROBE and VIEWPOINT parts can be used to display the results of the Nodal Analysis On The Schematic. Or you can click the V and I button to display the voltage and current.

  9. 5.0 DC SWEEP ANALYSIS • To find all DC voltages and currents of a circuit. • The DC Sweep is similar to the node voltage analysis, but adds more flexibility. • If we use the DC Sweep, we can simulate the circuit for several different values of voltage / current source in the same simulation.

  10. 5.1 BASIC DC SWEEP ANALYSIS How does Vo vary as V1 is raised from 0 to 25 volts?

  11. DC SWEEP PROBE: Trace Add. Click V(Vo) : voltage at the node Vo vs V1. We can also display current through any device of the circuit vs V1.

  12. 5.3 MAXIMUM POWER TRANSFER • Objective: To analyze what value of Rs in the circuit that will deliver maximum power to RL. • Max Power Theorem: Max power occurs when RL = Rs

  13. Adding parameters • Change RL value to {RL_val}N.B. name is unimportant but { } are mandatory • Add a PARAM symbol (Draw/Get New Part…/ Param) • Set up NAME1 and VALUE1 PARAM values (double-click on the symbol). • Click OK

  14. Set-up Parametric sweep • Setup a Parametric sweep (Analysis/Setup…/DC Sweep) • Click OK • Run DC sweep analysis • Example: MAXIMUM POWER TRANSFER • power absorbed by RL: • V(VL)*V(VL)/RL_val vs RL • P=V2/R

  15. RESULT Max power transfer occurs when RL_val=1kohm Result: Max power transfer occurs when RL_val = 1kohm

  16. Kirchoff’s Law Kirchoff’s Current Law = The algebraic sum of the currents entering a node is zero I1 I3 I2 I1 + I2 = I3 I1 + I2 – I3 = 0

  17. Cont. Kirchoff’s Voltage Law = The algebraic sum of the voltages around a closed path is zero. V1 = VR1 +VR2 +VR3 V1 – VR1 – VR2 – VR3 = 0

  18. 6.1 TASK 1: DC NODAL ANALYSIS Loop 2 1k(I2 - I1) + 2kI2 = -12 1kI2 – 1kI1 + 2kI2 = -12 -1kI1 + 3kI2 = -12 ---(2) Loop 3 3k(I3 - I1) + 2kI3 =12 3kI3 – 3kI1 + 2kI3 =12 -3kI1 + 5kI3 = 12 ---(3) I3 I2 I1 I1 Loop 1 3k (I1 - I3) + 1k(I1 – I2) = 12 3k I1 – 3kI3 + 1kI1 – 1kI2 = 12 4kI1 – 1kI2 – 3kI3 = 12 ---(1)

  19. Cont. • Solve the equation using Cramer’s Rule. Find the value of I1, I2 and I3. Then, find the DC node voltages for the circuit. Ax = b 4k -1k -3k -1k 3k 0 -3k 0 5k I1 I2 I3 12 -12 12 =

  20. PSPICE: AC ANALYSIS • AC Sweep: • To find Magnitude and Phase of voltage and currents  plots magnitude versus frequency  plots phaseversusfrequency. • Analysis: Bode Plots, gain and phase plots, and phasor analysis. • Applications: To see the frequency response of an amplifier and a filter. • Source: Vac or Iac.

  21. BODE PLOTS Magnitude vs Frequency Bode Plots  Frequency Response Phase vs Frequency Passive Filter (has R,L,C components) Filter Active Filter (has active components e.g: BJT)  normally operates as an amplifier. • Types of filter: • Low Pass Filter • High Pass Filter • Band Pass Filter • Band Stop Filter

  22. AC Analysis versus Transient Analysis

  23. Set-up VAC source • Set-up VAC* • DC=0 • used to find initial DC solution • ACMAG=1 • source p-to-p value during AC analysis • ACPHASE=0 • reference for phase measurements

  24. Set-up AC analysis and Probe • From Menu • Analysis/Setup… • or Toolbar - • Click “AC Sweep” • Enter as shown • Click “OK”

  25. Application:Measure the f3dB point of v_out using the cursors • In Probe: • Trace/Add, DB(V(v_out)) • To make cursors active - select • Place one cursor on nominal 0dB point • Move other cursor until “dif” shows difference of 3dB

  26. Measure the f3dB point of v_out using a goal function • N.B. to see a detailed explanation of this goal function and its parameters, select: • Trace/Goal Functions, LPBW, View • The g.f. can also be evaluated from this window (select Eval instead of View) In Probe: Trace/Eval Goal Function… Select: LPBW(1,db_level) Select: V(v_out) Enter 3 from the keyboard Click on OK

  27. Filter Design (3dB cutoff) – Example: Low Pass Filter

  28. Amplifier Gain Analysis • A=Vo/Vin • Vin=1V • A=Vo • Gain=20 * log10 A • Gain = 45.7 dB • Lower 3dB Freq=62.1 Hz • Upper 3dB Freq=6.9 MHz Use calculations to prove this simulations!

  29. Transient Analysis • Waveform (voltages or currents) versustime. • Pspice will simulate the time response of the circuit. • Sources: Vsin, Isin, Vpulse, Ipulse, etc. • The duration of simulation depends on the time constants in the circuit. • Specify the step size, or time increment, to be used by Pspice. • Use probe to view the results graphically. Probe will generate plots of voltage or current versus time.

  30. Transient Analysis Setup

  31. Final Time: Final Time is the length of simulation. F VSIN = 60 Hz T = 1/F = 1/60 s For 3 cycles simulation: 3T = 3 (1/60) = 50 ms = FINALTIME Print Step: Every Print Step seconds, the probe will print out the specified values in the output. Choose Print Step = 1ms No Print Delay: If we want to print data for the last 20ms of simulation: No-Print Delay = 50ms – 20ms = 30ms PSpice will save and print simulation data after this time. Step Ceiling: Leave it blank to get the fastest simulation time. PSpice will take the largest value of Step Ceiling allowed for simulation, but the plot maybe jagged. Reduce Step Ceiling to obtain smoother and nicer plot by divide with some numbers of points.It will increase simulation time. Step Ceiling= T/1000 points = (1/60) / 1000 = 0.01667ms Transient Analysis Setup:

  32. Example: Amplifier Voltage Swing

  33. Monte Carlo Analysis • INTRODUCTION: • To assign tolerance values of components. • Example: Resistors have values indicated in color code – and they never change. • In the real world, all resistors have tolerances, which specify how they might vary from their nominal values. • To determine the effects of such tolerance variations, PSpice offers Monte Carlo Analysis.

  34. MONTE CARLO • Used to observe how device tolerances can effect a design. • 2 types of Analysis: • Worst Case: to find maximum and minimum value of parameter given tolerances. • Monte Carlo: to estimate tolerance variation. • Device Model: • Uniform Distribution • Gaussian Distribution

  35. MODEL: Tolerance - Distribution • Resistor: • .MODEL R5pcnt RES(R=1 DEV/UNIFORM 5%) • .MODEL R5gauss RES(R=1 DEV/GAUSS 1.25%) • NPN BJT Transistor: • .MODEL QBf NPN(Bf=200 DEV/UNIFORM 150) • .MODEL Q2N3904B NPN(Is=6.734f DEV/UNIFORM 10% Xti=3 Eg=1.11) • Capacitor: • .MODEL CAP20_80 CAP(C=1.3 DEV/UNIFORM 38.461538%)

  36. Example:Voltage divider • Using 5% resistor with Gaussian distribution. Find gain, Av=Vo/Vin • By calculations: • 1) Nominal voltage gain. • 2) Worst case maximum gain. • 3) Worst case minimum gain. • By analysis – worst case analysis.

  37. Worst case analysis setup and output file

  38. Monte Carlo • To estimate % tolerance variation that pass specifications-in case max and min value exceed specifications.

  39. Monte Carlo output file • f=lV(Vo)-0.5l • Gain=(Nominal gain)-(deviation) • =(0.5)-(0.0202) • =0.4798 • % of nominal = [0.5/0.4798]*100 • =104.03% upper • Pass>0.01 [0.5-0.49=0.01]

  40. Monte Carlo – Probe as histogram

  41. histogram

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