ECEN 2612
PSpice AC Analysis (10.0 points)
Lab #3
Name:
Partner:
Objectives: To be able to use: (a) OrCAD PSpice to determine voltage and current amplitudes and
phase angles in an AC circuit, and (b) to use the AC sweep capability of PSpice to compute and plot
the frequency response of a circuit.
1. Single-Frequency Analysis (3.0 points)
The circuit has L = 100 mH, R = 1 kΩ, C = 0.05 μF, and the
sinusoidal source is described by:
Vg = 10 cos(2πf t + 90°) V
where f = 3 kHz.
In this step for single-frequency analysis, find the magnitudes
and phases of VL, VR, VC, and the current in the series circuit by performing an analytical solution
using phasor analysis. Then, you are to use PSpice to find these same magnitudes and phases. Finally,
compare your calculated values with the PSpice solutions.
A PSpice schematic representation of this circuit is shown below. Note the use of printer-device
parts. Construct this circuit in PSpice, using the VAC part for Vg. Print your schematic.
(a) PSpice current and voltage “printers” cause the
result of the analysis to be printed in the .OUT
output file. In order to get the desired output data,
we must edit the property spreadsheets for each of
these “printer” parts. The spreadsheet is accessed
by double clicking on each part. You must specify
the output to be from AC analysis by placing a “Y”
(for “yes”) in the column labeled AC. Also place a
Y in the columns labeled MAG and PHASE to have
output values in polar form.
Question: How can you get the outputs in rectangular form, i.e., placing a Y in what columns?
(b) Select AC Sweep as the type of analysis. Since we only need a single frequency, set the Start and
End “sweep” frequencies to the same value and the Number of Total Points to 1. Note that we
must specify the source file frequency value in hertz. Try doing this by omitting the End
frequency; describe what happens.
(c) Run the analysis and examine the output file (PSpice → View → Output File in the PSpice
window, or find it another way). Describe what happens, and what you do to find it.
Find the amplitudes and phase angles for each of the two voltages (VL and VC), and do the same for
the one current. List the results in your report and mark them in your printed .Out file. The
results will be found under the heading AC Analysis toward the end of the .OUT file. You could
save the .OUT file as a text (*.txt) file for future reference. Always put handwritten notes in your
.OUT files, too.
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2. Swept Frequency Analysis (3.0 points)
Usually AC Sweep is used to vary the frequency of the sinusoidal source, plotting the effect using
Probe. (Did you see “Probe” in (1c) above? Explain.) This type of analysis is called a "frequency
response." To run a frequency response, enable AC Sweep using the decade sweep type with 60 points
per decade, a start frequency of 150 Hz, and an end frequency of 50 kHz. Note that PSpice uses Hz
and not radians/sec!
Run the analysis and plot ‘IM(R)’. Run it again and plot ‘IP(R)’. Describe briefly on each plot
what you have plotted. Now, create one plot with two separate vertical axes to show both of these
values together. (Consult the instructor if you can’t figure this out.)
Using the cursor on the IM(R) plot, determine the resonant frequency (which means what?) and
both of the two frequencies at which the current is reduced to 70.7% of its peak value.
Figure out how to do another plot which gives the “voltage gain” of this circuit. That is, plot
M(V(C) / V(Vg)). Note: this formula may need revision to reflect the nomenclature used in your
circuit. Consult with the instructor if you have any issues.
3. Parametric Analysis (3.0 points)
Now, change the schematic by replacing the value of R with a "global parameter" named “r_value”
contained in curly brackets like this: {r_value}. The curly brackets are used to indicate a global
parameter. The default value of such a parameter is specified using the part named PARAM. Double
click the PARAM part to specify a default value of r_value; do not use the curly brackets there. Set
the default value of r_value to 1 kΩ, the original value of R.
During a swept-frequency analysis, a global parameter can also be swept using a "parametric
sweep." Examine the Parametric option under Options and notice the type of information required to
specify the Sweep Variable Type and Sweep Type. List the possible Sweep Variable Types and the
possible Sweep Types.
Use what you have just learned about AC Sweep analysis and about parametric sweeps to examine
the effect of the resistor value on the magnitude response of I(R). Use this list of values for R: 500 Ω,
1 kΩ, and 5 kΩ. Print and carefully label the Probe results in your report.
Report: Include all data, results, observations, and answers to questions, written neatly and legibly on the unlined side of
standard engineering paper. Use this lab sheet attached as a cover. (1.0 points)
Normally with PSpice work like this, at least one example schematic, one printed .OUT file (for Part 1 ONLY), and several
Probe outputs must be included. Write some NOTES and other careful labeling on your PSpice printouts. Set the
PSpice “print area” appropriately for your circuit schematic to allow for maximum clarity of your work. And print
PSpice work using the PSpice print capabilities. Do not copy/paste unless you can do that with good resolution.
This is due at the beginning of the next lab session.
P.Munro 12-Feb-2016 05:13 PM
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