Name: Daniel Bernard
Team Members: Benjamen Strobel and Jack Ladwig
ECE 2212
Lab #01 RC Circuits-Frequency and Time Domain Response Measurements
Due: February 2, 2012
Lab Coordinator: Stan Burns
Lab TA: Sukriti Subedi
Abstract:
This lab covers the creation of circuits on a breadboard, and their simulation in PSpice.
Calculations and data values were found or calculated from the oscilloscope or through analysis
of the PSpice circuit. Doing this allowed for better understanding of time and frequency domain
graphing and measurements using the instruments available to us. The numerous measurements
we recorded let us test out settings in both AC Sweep and Transient Analysis. The first time
domain response circuit was designed as an integrator circuit. This meant that if a square wave
was input to the circuit, the output wave would be triangular, and if a triangular wave was input,
a wave similar to a sine wave would be output. The second frequency domain response circuit
was a low pass filter.
Introduction:
This lab covers operation of an oscilloscope, function generator, power supply, and PSpice in order to simulate a
series of time domain response RC circuits. This also covers AC Sweep and Transient Analysis in PSpice.
Background:
In this lab we apply our knowledge of calculations for time constant, 𝜏, rise time, fall time, corner frequency, voltage
gain and signal phase.
Procedure:
Time domain response (integrator):
Simulate the circuit in Figure 1 below on both a breadboard, and in PSpice.
Drive the circuit with a 2 Volts peak-to-peak square wave, and adjust the frequency so that the curvature of the wave
can be seen.
Calculate corner frequency by measuring the time constant, 𝜏 at 𝑡63% , and comparing it to the calculation for 𝜏 = 𝑅𝐶.
Measure rise time by doing 𝑡𝑟 = 𝑡90% − 𝑡10% = 2.2𝑡
Then apply a triangular wave, and recalculate the previous values.
Frequency domain response (low-pass filter):
Using the same circuit from Figure 1, starting with an input frequency of 𝑓 = 100𝐻𝑧, measure the input voltage,
magnitude of gain, corner frequency, and phase shift.
Plot voltage gain as a function of frequency in dB from frequency ranges 100𝐻𝑧 ≤ 𝑓 ≤ 30𝑘𝐻𝑧.
Time domain response (differentiator)
Construct the circuit below in Figure 2 on both a breadboard and in PSpice.
Drive the circuit with a 2 Volt peak-to-peak, square wave, adjusting frequency so you can see the curvature of the
falling and rising.
Measure 𝑡37% and the fall time, = 𝑡10% − 𝑡90% = 2.2𝑡.
Frequency domain response:
Measure the high frequency gain and phase shift (𝑓 > 30𝑘𝐻𝑧).
Measure the gain and phase shift at low frequencies as well.
Vary frequencies from 30𝐻𝑧 ≤ 𝑓 ≤ 30𝑘𝐻𝑧.
Composite RC Circuit Frequency Response
Construct the circuit below in Figure 3 Revised, adjusting frequency so that you can see the key features.
Measure voltage gain and phase shift as a function of frequency of the circuit.
Measurements and Analysis of Results:
Time domain response (integrator):
𝑡63% = 100𝜇𝑠
𝜏 ≈ 𝑡63%
Frequency domain response (low-pass filter):
Simulated:
𝑡𝑟 = 2.2𝜏 = 2.2 ∗ 104.55𝜇𝑠 = 230𝜇𝑠
𝑡63% = 100𝜇𝑠
𝜏 ≈ 𝑡63%
PSpice:
𝜏 = 101𝜇𝑠, 𝑡𝑟 = 222𝜇𝑠
The actual resistance and capacitance may be off in the
actual circuit.
Time domain response (differentiator)
PSpice and the oscilloscope showed similar data, with the
capacitor charging and discharging as it jumped between high
and low levels of voltage.
𝐴𝑚𝑝𝑙𝑖𝑡𝑢𝑑𝑒 = 3.42𝑉
𝑡63% = 2.15𝑉,
98𝜇𝑠,
𝑃𝑆𝑝𝑖𝑐𝑒
𝑡63% = 2.14𝑉,
88𝜇𝑠,
𝑂𝑠𝑐𝑖𝑙𝑙𝑜𝑠𝑐𝑜𝑝𝑒
Frequency domain response:
2.8988 ∗ 0.63 = 1.826𝑉 𝑎𝑡 203.257 𝜇𝑠 = 𝑡63%
Op.
Ip.
Ip/Op (dB) Phase °
Freq. (Hz)
4.16
4.25
1.02
-9
100
4.04
4.28
1
-16.81
500
3.56
4.2
1.18
-34.65
1k
1.3
4.28
3.29
-72.77
5k
0.72
4.28
5.94
-80.05
10k
0.468
4.28
9.15
-85.01
15k
0.36
4.28
11.89
-86.5
20k
0.288
4.28
14.86
-88.24
25k
0.24
4.28
17.8
-88.21
30k
The created and simulated circuits match. There is similar
shaping on the curves going up and down as the capacitor
charges and discharges.
4.00 ∗ .37 = 1.48𝑉 𝑎𝑡 99.5𝜇𝑠 = 𝑡37% 𝑃𝑆𝑝𝑖𝑐𝑒
4.24 ∗ .37 = 1.57𝑉 𝑎𝑡 93.6𝜇𝑠 = 𝑡37% 𝑂𝑠𝑐𝑖𝑙𝑙𝑜𝑠𝑐𝑜𝑝𝑒
Composite RC Circuit Frequency Response
Ip.
Op.
Ip/Op
Phase °
(dB)
4.28
4.2
1.02
3.095
Freq.
(Hz)
45k
4.28
4.24
1.01
1.77
50k
4.28
4.28
1
1.01
60k
4.28
4.2
1.02
4.5
30k
4.28
4.16
1.03
9.7
10k
4.28
2.24
1.91
57
1k
4.28
1.27
3.37
73.55
500
4.28
0.33
12.97
158
100
Summary and Conclusion:
Overall this lab was simple in concept, but hard to follow. Not knowing or
understanding the voltage sources available to us, or how to use them really
put a lot of extra time into experimenting with how to make things work the
best. There could have been a better use of time, such as a more in depth
analysis, and instead having a class lecture on how to synthesize what
would be coming up in the lab, or have more in depth instructions written
out for the lab. My personal opinion is that the lab tutorial was lacking only
in how to use some of the analysis features (things like Phase measurements,
and dB readings were not taught until after we had the lab). Coverage of
different voltage sources would have been helpful in ECE 2006, and
analysis coverage could be more in depth a lecture before the first lab.
Despite that, I feel like I have a much better grasp now of how to use the
features of PSpice, and most applications should easier to complete from
here on out.
Once we knew which voltage sources were appropriate to use to
generate a specific type of wave, we were able to simulate what was
necessary.
This lab also gave a much stronger understanding of gain and
how a signal could become out of phase depending on the
circuit configuration.