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ELECTRIC CIRCUITS
ECSE-2010
Spring 2003
Class 38
ASSIGNMENTS DUE
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Today (Tuesday/Wednesday):
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Will do Computer Project #5 in Class (CP-5)
Activities 38-1, 38-2 (In Class)
Thursday:
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Experiment #9 Report Due
Activities 39-1, 39-2 (In Class)
Next Monday:
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Homework #14 Due
Experiment #10 Report Due
Computer Project #5 Report Due
Activity 40-1, Experiment 11 (In Class)
FINAL EXAM
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Wednesday, May 7
8 - 11 am
Sage 3303 for All Sections
2-8 1/2 x 11 inch Crib Sheets
Laplace Tables Will Be Included with
the Final Exam
Students with Conflict should Notify
Prof. Jennings ([email protected])
REVIEW
V
I
REVIEW
Series Resonance:
Parallel Resonance:
X  0 at    0
B  0 at    0
0 
1
LC
0 
1
LC
Qseries
1

R
Q parallel
C
R
L
L
C
Zeq ( 0 )  MINIMUM
Zeq ( 0 )  MAXIMUM
NOTES ON RESONANCE
• In “real” circuits, often do not have a
“pure” Series or pure Parallel situation:
• Inductors always have Rw
• Elements may not all be in series or parallel
• Will still have Resonance, but at a slightly
different Resonant Frequency
• May have Multiple Resonances in same Circuit
• Define Resonance as when X (series-like circuit)
or B (parallel-like circuit) => 0
• Let’s do a problem => Activity 38-1
ACTIVITY 38-1
20 
L


vL

v


vR 
100 
C

Find Z( )  R  jX
vC

Find 0 when X  0
AC PSPICE
• Now want to simulate AC Circuits
using PSpice:
• AC Sources
• C’s and L’s
• Usually want to look at behavior as
a function of Frequency:
• AC Sweep (Schematics)
• .ac Statement (Circuit file)
AC PSPICE-CIRCUIT FILE
• AC Voltage Source:
V 1 0 AC 10
• AC Current Source:
I
0 1 AC 3
• Do Not have to designate
frequency when specifying source:
• Do later with .ac statement
AC PSPICE-SCHEMATICS
• AC Voltage Source:
• Use VAC
• Doubleclick on VAC
• Designate Amplitude and Phase
• AC Current Source with Schematics:
• Use IAC; Designate same as VAC
• Do Not have to designate frequency
when specifying source:
• Do later with AC Sweep in Analysis
AC PSPICE
• Capacitors/Inductors:
C 1 0 2u
L 1 0 .1m
• Start “name” with C or L
• Connected between nodes 1 and 0 (+, -)
• C = 2 uF; L = .1mH
• Do Not need Initial Conditions for AC
Steady State
• Use IC’s when doing Transient Analysis
• Doubleclick C and L in Schematics to set
Values and IC’s
AC PSPICE
• .ac Statement:
.ac
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lin 400 10
16k
Perform AC Sweep (Sweep AC
frequencies)
Perform a linear sweep (will do decade
sweeps later)
Divide frequency range into 400 points
starting frequency = 10 Hz (note: f)
ending frequency = 16 kHZ
AC PSPICE
• In Schematics:
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Doubleclick Set Up Analysis
Choose AC Sweep and Doubleclick
Choose Type of Sweep
Choose Start and End Frequencies
Choose Number of Points
Remember PSpice uses Frequencies in Hz
ACTIVITY 38-2

v 100 
i
2 F
0.2 mH

If R W  0; f 0  8 kHz and Qparallel  10
Let R W  10
9
; 2 
RW
ACTIVITY 38-2
• Similar to Activity 38-1:
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Not a “Pure” Parallel Resonant Circuit
Inductor has Winding Resistance
Want to see how this affects Resonance
Let Rw = 10-9 ~ 0, 2 ohms
When Rw = 0, fo ~ 8 kHz, Qparallel ~ 10
See what happens when Rw = 2 ohms
Let’s Practice using Schematics
COMPUTER PROJECT 5
100 
iin
vin
5
15 
i1
6 mH
i2
12 mH
40 nF
COMPUTER PROJECT 5
• Circuit is both “Series-like” and
“Parallel-like”:
• Will have both Series and Parallel
Resonances
• Resonances occur at different frequencies
• Identify by Minimum or Maximum of /Z/
• /Z/ is a Minimum at Series Resonance
• /Z/ is a Maximum at Parallel Resonance
COMPUTER PROJECT 5
• PSpice wants frequencies in Hertz:
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Project asks to sweep 
Must convert  = 2  f
Plot as function of  = f * 6.28
Use Linear X Axis
• Note: Zin = Vin / Iin
• Vin = 1 /0 o Volts
• => Yin = Iin /1 Siemons