Name: _________________________

ECE3741 Section: _________________________

Final Exam GTID: _________________________
Table: _________________________

Instructions: Signature: _______________________

1. There are 33 Questions worth varying points
2. This Exam is Closed Books, Closed Notes.
3. You are allowed a calculator
4. This Exam is Personal (There should be no discussion among group members).
5. You will have 90 minutes to take the exam
6. Sign the signature line above to signify that you have read and understand the
instructions.

True False Section (2 Points Each)

1. A full bridge rectifier changes the frequency of the input signal

2. A high-pass filter can be used to remove the high frequency components

3. A non-inverting amplifier cannot have a gain less than 1

4. The cutoff frequency is always different from the resonant frequency in a Second Order
Active Filter

5. An RC circuit with larger time constant will take longer to decay

6. A smaller feedback resistor will result in a larger voltage difference between the upper
and lower voltage threshold in a Schmitt trigger

7. A complementary MOSFET pair in a class D amplifier will invert a PWM

8. A sine wave looks like a single spike in the frequency domain

9. Adding a load to an active high-pass filter will increase the cutoff frequency of the filter

10. A wide PWM pulse corresponds to a low voltage input

11. A relaxation oscillator is a combination of Schmitt trigger and RC charging circuit

12. A comparator outputs the larger of the two inputs

13. The output of a Schmitt trigger affects the threshold voltage of the non-inverting input

14. A MOSFET acts like a current-controlled switch

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 15. An active filter can have a passband gain less than 1

Short Answer Section – (3 Points Each)

16. A JFET can be used as all the following except:
a. Variable resistor
b. Voltage divider
c. Amplifier
d. Attenuator
17. Draw the frequency domain of the following signal:
𝑓(𝑡) = 2 sin(2000𝜋𝑡) + 6sin⁡(20𝜋𝑡)

18. Find 𝑅1 , 𝑅2 , 𝑅3 if
𝑅𝑓 = 30𝑘Ω
𝑉𝑜 = −(12 + 8 sin(5𝜔𝑡) + 7 cos(𝜔𝑡))
𝑉1 = cos(𝜔𝑡) ; 𝑉2 = 2 sin(5𝜔𝑡) ; 𝑉3 = 3

𝑅1 = _________ 𝑅2 = _________ 𝑅3 = _________

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19.

a. What is the relationship between the input and the output? (1)

b. In what cases would you use the following circuit? (2)

20. Explain the purpose of SPAN and CENTER on an oscilloscope’s FFT plot

21. What is the difference between a MOSFET and a JFET?

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 22. The LED has a forward bias voltage of 0.7V and a minimum required current of 2mA.
Find the minimum voltage of the JFET required to turn on the LED. Assume the JFET
resistance curve continues past 7500Ω.

JFET Resistance Vs. Gate Voltage

0
0 1000 2000 3000 4000 5000 6000 7000
-0.05
Control Voltage

-0.1

-0.15

-0.2

-0.25

-0.3
JFET Resistance

Vmin = ______________

23. Match the waveforms to the nodes on the circuit that generate them.

-1
0 0.5 1 1.5 2 2.5 3

-6

-11

Solid Line:______________ Short Dashes:______________ Long Dashes:______________

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24. The following PWM is made from a 4Vpp ramp function with a 2V offset. Use this
information to answer the following questions.

a. Duty Cycle
b. Vin
c. Comparator source voltage

25. Given the following circuit and two input voltages in the same figure, draw the output
voltage over the graph. Assume Vs+=1.5 and Vs-=-1.5. Assume an Ideal Op-Amp.

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26. Given VIN = 1VPP, assign RA, RB, and R2 to get VOUT = 3VPP

27. Consider the circuit shown the figure. Given that, V = 15V, R1 = 8kΩ, R2 = 5kΩ, R3 =
10kΩ.

a. What is the current through R1?

b. What is the voltage across the Resistor R2?

c. What is the current through R3?

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Long Answer Section – (5 Points Each)
28.

a. What is the name of this circuit? (1)

b. What is the value of the time constant in this circuit? (1)

c. What happens to the 𝑉𝑜𝑢𝑡 if you remove R1 from the circuit? (2)

d. 𝑉𝑜𝑢𝑡 can be negative (1)

TRUE FALSE

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29. Answer the following question based on the following frequency response of an RC filter

a. Label the cutoff frequency, pass band, and stop band on the plot. (2)

b. If the capacitance is 1𝜇𝐹 what will the resistance be for this frequency response?
(2)

c. What is the time constant of this circuit? (1)

30. Consider the circuit below

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 a. What is the purpose of this circuit? (2)

b. If 𝑉𝑑𝑑 = 6𝑉, for what value of 𝑉𝑖𝑛 will the 𝑉𝑜𝑢𝑡 be 6V (assume ideal MOSFET)
(1)

c. How does you circuit behave if you interchange the p-channel and n-channel with
same connections for gate, source, drain, and bulk. (2)

31. Determine the natural frequency, pass band gain, and the quality factor of the following
second order filter

a. Fo =
b. K=
c. Q=
d. Fc should be [greater than / less than / equal to] Fo (select one)

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32. Use the following circuit to answer the questions below (assume ideal diode operation).
Sketch both outputs on the same plot as the input.

a. What is the name of this circuit?

b. What is the output amplitude?

c. What is the output frequency?

d. If we added a .1µF capacitor in parallel with the resistor, what would the output
be? Draw it below.

Sketch Output Input

3
Voltage

0
0 0.05 0.1 0.15 0.2 0.25

-3
Time

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33. Given the following circuit with the LM311 Comparator answer the following:

a. The Transistor is off then COL_OUT is:

b. The Transistor is on then COL_OUT is:
c. Replace R_p with a wire; when the Transistor is off then COL_OUT is:
d. Replace R_p with a wire; when the Transistor is on then COL_OUT is:

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