The document discusses basic circuit simulation concepts using OrCAD software. It covers capacitors and inductors in series and parallel, reviews their frequency response characteristics, and how they can be used to create filters. It also discusses decibels, cursor controls in OrCAD, common problems in simulations, transformers, diodes, rectification circuits, and voltage regulators.

1. Basic Circuit Simulation using
OrCAD
Prof. Anish Goel

2. Capacitors in Series
 Series Capacitors add like Parallel Resistors:
 1/CT = 1/C1 + 1/Cn
 CT = .909uF
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3. Capacitors in Parallel
 Parallel Capacitors add like Series Resistors:
 CT = C1 + Cn
 CT = 11uF
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4. Inductors in Series
• Series Inductors add like Series Resistors:
• LT = L1 + Ln
• LT = 11uH
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5. Inductors in Parallel
 Parallel Inductors add like Parallel Resistors:
 1/LT = 1/L1 + 1/Ln
 LT = .909uH
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6. Capacitor Review
 Starts as short circuit, ends as open circuit
 iC = C*dVC/dt
 Open circuit at low frequencies
 Short circuit at high frequencies
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7. Inductor Review
 Starts as open circuit, ends as short circuit
 VL = L*dI/dt
 Short circuit at low frequencies
 Open circuit at high frequencies
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8. Filters
 Use frequency response characteristics of C and L to
filter frequency components out of a time domain signal.
 Low Pass
 High Pass
 Band Pass
 Band Stop
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9. Low Pass Filters
 RC Low Pass: fcut off frequency = 1/(2πRC)
• Component selection
• RC vs. RL filters
 RL Low Pass: fc = R/(2πL)
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10. AC Analysis (freq)
 Logarithmic plot (count by decades)
 fc defined as –3dB of input, “Half power point”
 Copy paste data points to excel!
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11. Decibels
 Measure of gain. Instead of saying gain is 100,000x, some
engineers prefer to say it as 100dB.
 Power gain: dB = 10 log(Po/Pi)
 Voltage gain: dB = 20 log(Vo/Vi)
 Always a relationship
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12. Decibels (cont’d)
 Useful values:
 0dB = 1x
 3dB = 2x
 6dB = 4x
 10dB = 10x
 20dB = 100x
 30dB = 1000x
 3dBm is 3dB above 1mW
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13. Cursor Control
 Cursor 1:
 left click
 left/right arrows
 Cursor 2:
 right click
 Shift left/right arrows
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14. Cursor, Mark Label
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15. .707?
 Because we are comparing gains in voltage, not power, we
must use 20log(Vo/Vi).
 10^(-3dB/20) = .707V
 So,Vo = .707Vi at the cut off frequency
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16. Bode Plot (dB, logarithmic)
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17. Common Problems
 Q: Simulation not making sense
 A: Make sure you how things are connected.
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18. • RC High Pass: • RL High Pass:
• fc = 1/(2πRC) • fL = R/(2πL)
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19. Band Pass
HP LP
BW = (fc + 3dB) – (fc – 3dB)
BW = 200.171kHz – 494.694Hz = 199.676kHz
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20. Response
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21. Band Stop
HP LP
BW = 16.216kHz –6.0833kHz = 10.133kHz
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22. Response
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23. Transformer
 Easy to “Step down” or “Step up” an AC voltage
 (This is why AC is used for home power delivery instead of
DC.)
 VP/VS = NP/NS => VS = VPNS/NP
 Excellent DC filter because VS = NS*dΦ/dt
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24. In PSPICE…
 Coupling = 1
 Lx_Value = Nx2
 should be between 1mH and 1H
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25. Diode
 Allow current to flow only in 1 direction
 Flow from left (annode+) to right (cathode-) is forward
biased.
 Diode causes a voltage drop due to its activation voltage.
 Silicon - .7V
 Germanium - .3V
 Cathode connected to a battery is reversed biased. (blocked)
 Perform DC Sweep and Transient Response (use D1N4002)
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26. Activation Voltage
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27. Transient Response
Half Wave Rectifier
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28. Half Wave Rectifier
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29. Full Wave Rectification
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30. Bridge Rectifier
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31. In PSPICE…
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32. Full Wave Rectifier
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33. Smoothing
 Use capacitor to smooth the ripples of the rectified
wave form.
(Negative voltage)
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34. Regulators
 Not in student addition
 Outputs a clean regulated voltage
 LM317 and 337 are +/- 2-18V variable regulators
 LM7805 is 5V regulator
 Input must be relatively steady or else regulator will fail.
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