Download EGR 277 – Digital Logic

Lecture #8
EGR 272 – Circuit Theory II
Reference:
• Read Ch. 1-3 in Schematic Capture Using Cadence PSPICE for general
info on PSPICE
• Read Ch. 5-6 in Schematic Capture Using Cadence PSPICE on AC Sweep
and Transient Analysis
• The following items are available from the instructor or can be obtained
from his web page.
 PSPICE Assignment Requirements
 PSPICE SAMPLE REPORT
 AC Analysis - Phasors
 AC Analysis - Transients
PSPICE Demonstration
• A demonstration will be performed in class. The following pages highlight some
of the key concepts. Also refer to the examples listed above.
• It is assumed that students already have knowledge of analyzing DC circuits
using PSPICE.
• The focus of this demonstration will be to illustrate the differences when
analyzing AC circuits.
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Lecture #8
EGR 272 – Circuit Theory II
Sinusoidal sources - two new types of sources will be introduced for AC circuits:
1) VAC or IAC
• This source is used for phasor analysis (for finding phasor voltages or
currents and
• also for graphing with frequency on the x-axis in PROBE.
• The magnitude and angle for the phasor source is specified.
• This source is typically used with an AC SWEEP analysis.
• Note that the source does not specify whether it is referenced to a sin or a
cos.
• If you think of the source as a cos source, then the results are also
reference to a cos.
V4
1Vac
0Vdc
Part: VAC
I3
1Aac
0Adc
Part: IAC
V4
ACMAG = 100V
ACPHASE = 30degrees
Part: VAC with properties changed
for a phasor voltage of 10030
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Lecture #8
EGR 272 – Circuit Theory II
2) VSIN or ISIN
• This source is used for TRANSIENT analysis (graphing sinusoidal
waveforms vs time).
• Specifications are given for max value, DC value, frequency (in Hz), and
delay.
• Note that the source is reference to a sin. Add a delay if it is important to
reference to a cos waveform (this is generally not important).
V5
VOFF =
VAMPL =
FREQ =
Part: VSIN
I4
IOFF =
IAMPL =
FREQ =
Part: ISIN
V5
VOFF = 0V
VAMPL = 100V
FREQ = 1000Hz
PHASE = 30degrees
Part: VSIN with properties
changed for a time domain
voltage of 100sin(2000t + 30) V
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Lecture #8
EGR 272 – Circuit Theory II
Analysis methods - two primary types of analysis are used with AC circuits
1) AC Sweep
• In this method frequency (in Hz) is varied.
• This method is typically used with VAC or IAC sources.
• To analyze at a single frequency, use the same starting and stopping
frequency and specify 1 for the number of points (see example below).
• Include voltage or current printers to display the results in the .OUT file.
• To generate a graph with frequency on the x-axis in PROBE, use a range of
frequencies.
• The .OUT file may also contain node voltages by default, but these are DC
node voltages and are typically equal to zero.
Simulation Settings
for AC Sweep
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Lecture #8
EGR 272 – Circuit Theory II
2) TRANSIENT Analysis
• In this method time is varied.
• This method is typically used with VSIN or ISIN sources.
• Specify the range of time values that are to be placed on the x-axis in
PROBE (see the sample screen on the next page).
• Note: AC analysis or Sinusoidal Steady-State Analysis by definition
ignores the initial transient response. But PSPICE can only perform a
complete analysis, which includes both the transient response and the
steady-state response. Therefore, you may see some strange initial
behavior when graphing sinusoidal waveforms. If you only want to graph
them in their steady-state form, then perform an analysis that is longer than
necessary and only view the last portion. For example, if you wish to view
the waveforms for 1ms, then you might perform a transient analysis from 0
to 10ms and zoom in on the portion from 9ms to 10ms once in PROBE.
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Lecture #8
EGR 272 – Circuit Theory II
Simulation Settings - Transient Analysis
The simulation settings shown below could be used if 5 periods of the waveform
100sin(2000t + 30) V are to be graphed. Note that w = 2000 so f = w/  =
1000 Hz and T = 1/f = 1ms.
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Lecture #8
EGR 272 – Circuit Theory II
Current Printers and Voltage Printers
Recall from the analysis of DC circuits using PSPICE that printers are ignored unless:
1) A DC sweep is performed.
2) The DC property is set (such as DC = V(R4) or DC = V(A,B)).
Similarly, printers in AC circuits are ignored unless:
1) An AC Sweep is performed.
2) The AC attribute is set (such as AC = VM(L2), indicating the magnitude of the
voltage across L2, or AC = IP(C1), indicating the phase (in degrees) of the
current through C1). It is also required so specify YES for the properties MAG
and PHASE.
AC = IM(R4), IP(R4)
MAG = Y es
PHASE = Y es
Sample use of printers
in an AC circuit
AC = VM(R5), VP(R5)
MAG = Y es
PHASE = Y es
Voltage printer
(part VPRINT2)
IPRINT
R4
R5
1k
1k
V4
ACMAG = 100V
ACPHASE = 30degrees
Current printer
(part IPRINT)
1k
R6
0
1uF
C1
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Lecture #8
EGR 272 – Circuit Theory II
Current Printers and Voltage Printers
Recall from the analysis of DC circuits using PSPICE that printers are ignored unless:
1) A DC sweep is performed.
2) The DC property is set (such as DC = V(R4) or DC = V(A,B)).
Similarly, printers in AC circuits are ignored unless:
1) An AC Sweep is performed.
2) The AC attribute is set (such as AC = VM(L2), indicating the magnitude of the
voltage across L2, or AC = IP(C1), indicating the phase (in degrees) of the
current through C1). It is also required so specify YES for the properties MAG
and PHASE.
AC = IM(R4), IP(R4)
AC = VM(R5), VP(R5)
MAG = Y es
PHASE = Y es
MAG = Y es
PHASE = Y es
IPRINT
Sample use of printers
in an AC circuit
R4
R5
1k
1k
V4
ACMAG = 100V
ACPHASE = 30degrees
1k
R6
0
1uF
C1
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