# Lab1: Lab Procedures, policies and Equipment solution

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Objectives
• To prepare materials needed for the semesters’ lab assignments.
• To review techniques and procedures required for professional laboratory work.
• To gain experience using the function generator, power supply, oscilloscope and multimeter located in the ECE
Circuits Lab (EL 104).
Parts and Equipment Required
Components and Materials Needed:
• 10kΩ resistor (1)
• 1kΩ resistor (1)
• 1nF capacitor (1)
• solderless breadboard/superstrip (1)
Equipment to be Used:
• Digital Multimeter (1)
• Oscilloscope (2 channels)
• Function generator (1)
• Banana-to-alligator cables (1 pair, red and black)
• BNC-to-BNC cable (2)
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ECE 3410– Microelectronics I Lab 1: Lab Procedures, policies and Equipment
• BNC-to-alligator cable (1)
• Oscilloscope probe (2)
1 Pre-Lab Exercises
Exercise 1. Consider the following signal:
vIN (t) = 1V+ (2V)sin(2π ft),
for a frequency of f = 10kHz. Describe the magnitude spectrum, |VIN (f)|, associated with this signal.
Exercise 2. Suppose the signal from Exercise 1 is provided as input to the circuit shown in Fig. 1. Give expressions
for the output signal, vOUT (t).
1kΩ
10kΩ
vIN (t) vOUT (t)
Figure 1: Circuit for Exercise 2.
Exercise 3. Suppose the signal from Exercise 1 is provided as input to the circuit shown in Fig. 2. Evaluate the gain
|H(f)| (in dB), the phase shift φ = ∠H(j f) (in degrees) and the output signal vOUT (t) (in Volts) at three
frequencies, f1 = 1kHz, f2 = 10kHz, f3 = 50kHz. What kind of filter circuit is this, and what is its 3dB
cutoff frequency, in kHz? Finally, evaluate the phase φ at the 3dB cutoff frequency. Hint: The 3dB
cutoff frequency is where the output amplitude falls to 0.707 of its maximum value. Also recall that the
gain, in decibels, at specific frequency f is given by
Gain(dB) = 20log10 
vOUT (f)
vIN (f)

,
Exercise 4. Suppose the signal from Exercise 1 is provided as input to the circuit shown in Fig. 3. Evaluate the gain
|H(f)| (in dB), the phase shift φ = ∠H(j f) (in degrees) and the output signal vOUT (t) (in Volts) at three
frequencies, f1 = 1kHz, f2 = 10kHz, f3 = 50kHz. What kind of filter circuit is this, and what is its 3dB
cutoff frequency, in kHz? Finally, evaluate the phase φ at the 3dB cutoff frequency.
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ECE 3410– Microelectronics I Lab 1: Lab Procedures, policies and Equipment
10kΩ
1nF
vIN (t) vOUT (t)
Figure 2: Circuit for Exercise 3.
1nF
10kΩ
vIN (t) vOUT (t)
Figure 3: Circuit for Exercise 4.
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ECE 3410– Microelectronics I Lab 1: Lab Procedures, policies and Equipment
2 Physical Experiments
Procedure 1. Connect the banana cables to the Digital Multimeter on your lab bench. Set the Multimeter to measure
Ohms, and obtain precise measurements for the two resistors used in this lab. Record the values in your
lab book.
Procedure 2. Using a BNC cable, connect the Main signal output from the Function Generator to the CH 1 input on
the oscilloscope. Also connect the SYNC output from the Function Generator to the EXT TRIG input
on the oscilloscope. Perform the following steps:
Step A. Press the TRIG MENU button. Using the Menu buttons along the right side of the oscilloscope
display, press the Source button until it displays Ext.
Step B. Press the Channel 1 button. You should see the Channel 1 Menu options appear along
the right side of the scope display. Make sure that it reads DC Coupling, BW Limit OFF,
Probe 1X and Invert OFF.
Step C. Adjust the Volts/Div and Seconds/Div knobs to get 1 V per division and 100 µs per division,
respectively.
Step D. Adjust the Amplitude, Offset and Frequency knobs on the Function Generator until the
settings match the waveform specified in Prelab Exercise 1. Set the Function Generator to a
sine wave signal source. Use the oscilloscope display to verify your settings. Note: To adjust
the offset voltage on the Function Generator, you will have to pull out on the knob to unlock its
setting.
Step E. Press the Measure button on the oscilloscope. Set the Source to be Channel 1 using the
Menu buttons on the side of the scope. Using the measurement options, obtain precise measurements
for the signal’s frequency, its peak-to-peak amplitude, and it average value (i.e. the offset
voltage). Record these values in your lab book.
Procedure 3. Press the Math button on the oscilloscope. Perform the following steps:
Step A. Using the Menu buttons along the right side of the oscilloscope, set the Math operation to FFT.
Adjust the Seconds/Div and Volts/Div knobs to read 50 kS/s and 10 dB per division,
respectively.
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ECE 3410– Microelectronics I Lab 1: Lab Procedures, policies and Equipment
Step B. Record the spectrum displayed on the oscilloscope. Does it match your expectations? Take note
of any anomalies, and offer hypotheses to explain them.
Step C. On the Function Generator, change the signal type to a square wave. How does this change the
magnitude spectrum?
Step D. Now change the signal type to a triangle wave. How does this change the magnitude spectrum?
Procedure 4. Using your breadboard, connect a circuit to match the schematic in Fig. 1. Perform the following steps:
Step A. Set the Function Generator to produce a sine wave. Press CH 1 Menu to turn off the FFT
display on the oscilloscope. Verify that the Function Generator settings still match the waveform
specified in Exercise 1.
Step B. Using a BNC-to-alligator cable, connect the Function Generator to your circuit. The alligator
clips should connect to vIN (red) and ground (black).
Step C. Connect the two probes to the oscilloscope. Connect both of the probes’ black alligator clips to
ground on your circuit board. Then connect the Channel 1 probe to vIN, and the Channel 2 probe
to vOUT.
Step D. Adjust the oscilloscope so that both signals are visible. Adjust both Channels to display 1 V per
division. Using the Vertical Position knobs, position the signals so that their reference
points match (look for the little arrow on the left side of the scope display).
Step E. Using the Measure key, obtain precise measurements for the peak-to-peak amplitude and average
value of each signal. Do the measurements match your expectation? Explain any difference.
Procedure 5. Change the circuit on your breadboard to match the one shown in Fig. 2, and perform the following
steps:
Step A. Connect the Channel 1 probe to vIN and the Channel 2 probe to vOUT. Set the input frequency to a
low value of f1 = 1kHz.
Step B. Press the Math button and activate the FFT function. Set the Source to be CH 2. Adjust the
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ECE 3410– Microelectronics I Lab 1: Lab Procedures, policies and Equipment
VOLTS/DIV and SEC/DIV knobs so that the display reads 10 dB per division and 50 kS/s,
respectively.
Step C. You should see a peak at 1 kHz. Adjust the Horizontal Position knob so that the peak is
centered on the oscilloscope display, then zoom in by pressing the FFT Zoom button. Zoom in
on the magnitude display by adjusting the Vertical Position knob above CH 2. Change
the VOLTS/DIV setting to 2dB per division and locate the peak on the display.
Step D. Press the CURSOR button and set the Type to Magnitude. Position Cursor 1 at the top of
the peak, and position Cursor 2 3dB below the magnitude of Cursor 1 (watch the Delta
measurement on the right side of the display to see when you reach 3dB).
Step E. Now change the FFT Zoom to X1 and slowly increase the frequency on the Function Generator
until the peak precisely touches Cursor 2.
Step F. Re-center the peak on the display by adjusting the Horizontal Position knob, and change
the FFT Zoom to X10. Change the cursor Type to Frequency. Adjust one of the cursors
to align with the new peak on the FFT display. This is the 3dB cutoff frequency for the circuit.
Record this frequency in your lab book. Does it match your expectation from Prelab Exercise 3?
Explain any differences.
Procedure 6. Change the circuit on your breadboard to match the one shown in Fig. 3, and perform the following
steps:
Step A. Repeat the steps from Procedure 5. This time, you will sweep from a high frequency to a lower
frequency.
Step B. Adjust the SEC/DIV so that the display reads 100 kS/s.
Step C. Set the Function Generator to 40kHz. As before, locate the peak magnitude with Cursor 1,
and position Cursor 2 to a point 3dB below Cursor 1.
Step D. Slowly decrease the frequency on the Function Generator until the peak precisely touches Cursor
2.
Step E. Switch the cursors to Type Frequency, and align one of the cursors with the peak. This is
the 3dB cutoff frequency of your high-pass circuit. Record this value in your lab book. Does it
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ECE 3410– Microelectronics I Lab 1: Lab Procedures, policies and Equipment
meet your expectations? Offer a hypothesis for any deviation.
Procedure 7. A digital oscilloscope takes discrete samples.When the sample rate is lower than double the frequency
you are looking at, the apparent frequency will be lower than actual frequency. To observe this phenomenon,leave
your circuit in the configuration of Procedure 6 Increase the frequency beyond the right
edge of the FFT display. Continue increasing the frequency, up to 200kHz, and observe the FFT display.
What happens as you increase the frequency? Explain what you observe, and comment on how this
phenomenon may affect future lab experiments.
3 Post-Lab
In your lab book, write a summary of your findings. In particular, comment on the measured behavior of the voltage
divider, low-pass and high-pass circuits. Can your measurements be precisely predicted by using formulas and your
measured resistor values? In your opinion, how precise is your measurement of the cutoff frequencies for the low-pass
and high-pass circuits? What steps could be taken to improve the precision? Also, comment on the effect observed in
Procedure 7. What problems could this cause for future experiments, and how can you avoid those problems?
Finally, write a brief report describing y