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Unit 5 - Practice Quiz

ELE205

1 Which of the following elements are used to construct a passive filter?

A. Resistors, Capacitors, and Op-Amps
B. Resistors, Inductors, and Capacitors
C. Transistors and Capacitors
D. Op-Amps and Inductors

2 In a symmetrical T-network, the characteristic impedance is given by which formula, where is the total series arm impedance and is the shunt arm impedance?

A.
B.
C.
D.

3 What is the relationship between the characteristic impedance of a T-network () and a -network () composed of the same series and shunt impedances?

A.
B.
C.
D.

4 In a pure reactive network, the propagation constant . What condition defines the passband?

A. and
B. and
C. and
D.

5 What defines a Constant-K filter?

A. The sum of series and shunt impedances is constant.
B. The product of series () and shunt () impedances is a frequency-independent constant ().
C. The difference between series and shunt impedances is constant.
D. The ratio of series to shunt impedance is constant.

6 For a Constant-K Low Pass Filter using T-section, the series arm consists of __ and the shunt arm consists of __.

A. Capacitors; Inductors
B. Inductors; Capacitors
C. Resistors; Capacitors
D. Inductors; Resistors

7 Calculate the cut-off frequency () of a Constant-K Low Pass Filter given and .

A.
B.
C.
D.

8 In the design of a Constant-K High Pass Filter, what are the design equations for and given cut-off frequency and design impedance ?

A.
B.
C.
D.

9 What is the primary disadvantage of a simple Constant-K filter?

A. It uses active components.
B. The attenuation in the stopband rises very slowly (gradual cut-off) and varies with frequency.
C. It cannot be designed for high frequencies.
D. It has zero phase shift in the passband.

10 Which filter type is used to overcome the slow attenuation rate of Constant-K filters?

A. RC Filter
B. m-derived filter
C. RL Filter
D. All-pass filter

11 In an m-derived low pass filter, the resonant frequency (frequency of infinite attenuation) is related to the cut-off frequency by:

A.
B.
C.
D.

12 The value of 'm' in an m-derived filter lies in the range:

A.
B.
C.
D.

13 What is the formula for 'm' in an m-derived Low Pass Filter?

A.
B.
C.
D.

14 In a Series m-derived Low Pass T-section, what component is added to the shunt arm?

A. An inductor in series with the shunt capacitor
B. A capacitor in parallel with the shunt inductor
C. A resistor
D. An inductor in parallel with the shunt capacitor

15 What is the characteristic impedance of a Series m-derived T-section compared to the prototype Constant-K section?

A. It is completely different.
B. It is equal to the prototype at all frequencies.
C. It is equal to the prototype .
D. It is zero.

16 Why are Composite Filters used?

A. To save components.
B. To combine the advantages of Constant-K (passband), m-derived (sharp cut-off), and half-sections (impedance matching).
C. To reduce the gain of the circuit.
D. To create oscillators.

17 In a composite filter, what is the purpose of the terminating half-sections?

A. To provide sharp cut-off.
B. To double the voltage.
C. To make the image impedance constant () over the passband for matching.
D. To block DC.

18 What specific value of 'm' is typically used for the terminating half-sections to ensure flat characteristic impedance?

A.
B.
C.
D.

19 Which of the following is a major advantage of Active Filters over Passive Filters?

A. They require no power supply.
B. They can handle high voltage and current.
C. They eliminate the need for bulky inductors.
D. They are inherently stable.

20 Active filters are generally restricted to which frequency range?

A. Microwave frequencies (> 1 GHz)
B. Radio frequencies
C. Audio and low radio frequencies
D. X-ray frequencies

21 Which component is NOT used in a standard Active Filter design?

A. Op-Amp
B. Resistor
C. Capacitor
D. Inductor

22 What is the voltage gain capability of an Active Filter?

A. Always less than 1 (Attenuator)
B. Always exactly 1 (Buffer)
C. Can be greater than 1 (Amplification)
D. Always 0

23 A First-Order Active Low Pass Filter provides a roll-off rate of:

A. -20 dB/decade
B. -40 dB/decade
C. -60 dB/decade
D. -80 dB/decade

24 In a standard non-inverting First-Order Active Low Pass Filter, where is the capacitor placed?

A. In series with the input signal.
B. In the feedback loop of the Op-Amp.
C. In parallel with the input resistor to ground (shunt arm) at the non-inverting terminal.
D. In series with the output.

25 The cut-off frequency for a First-Order Active Low Pass Filter with input resistor and shunt capacitor is:

A.
B.
C.
D.

26 In a First-Order Active High Pass Filter, the positions of the resistor and capacitor at the non-inverting input are:

A. Swapped compared to the Low Pass Filter.
B. Ideally the same as the Low Pass Filter.
C. Both in series.
D. Both in parallel.

27 The passband gain () of a non-inverting active filter is determined by:

A. The RC time constant.
B. The feedback resistor () and input resistor () of the Op-Amp.
C. The frequency of the signal.
D. The input voltage amplitude.

28 What is the phase shift at the cut-off frequency for a First-Order Active Low Pass Filter?

A. -90 degrees
B. -45 degrees
C. 0 degrees
D. +45 degrees

29 Which of the following is a limitation of Passive Filters compared to Active Filters?

A. They require a power supply.
B. Loading effect: The source and load impedances affect the filter characteristics.
C. Limited bandwidth.
D. High noise.

30 If you need to design a filter with a cut-off frequency of 50Hz, which type is preferred and why?

A. Passive, because inductors are small at 50Hz.
B. Active, because passive inductors required for 50Hz would be extremely large.
C. Passive, because it has gain.
D. Active, because it uses more power.

31 In a T-section network, if is the open-circuit impedance and is the short-circuit impedance, then is:

A.
B.
C.
D.

32 A Band Pass Filter allows frequencies:

A. Below a certain cut-off.
B. Above a certain cut-off.
C. Within a specific range ( to ).
D. Outside a specific range.

33 A Band Stop (Notch) Filter is formed by:

A. Cascading a LPF and a HPF with overlapping passbands.
B. Connecting a LPF and HPF in parallel.
C. Series combination of LPF and HPF where cut-off frequencies do not overlap in a specific way.
D. A single capacitor.

34 What is the stopband attenuation rate of a Second-Order Active Filter?

A. -20 dB/decade
B. -40 dB/decade
C. -60 dB/decade
D. -10 dB/decade

35 Which parameter determines the selectivity or sharpness of an Active Band Pass Filter?

A. Gain
B. Q-factor (Quality Factor)
C. Input Voltage
D. Supply Voltage

36 Design a Constant-K Low Pass Filter (T-section) with and Hz. The value of is approximately:

A. 191 mH
B. 95.5 mH
C. 318 mH
D. 600 mH

37 In the design of the filter in the previous question, what is the value of the shunt Capacitor ?

A. 0.53 F
B. 1.06 F
C. 0.26 F
D. 10 F

38 The 'Butterworth' response in active filters is characterized by:

A. Ripples in the passband.
B. Ripples in the stopband.
C. Maximally flat response in the passband.
D. Fastest roll-off.

39 The 'Chebyshev' filter response is known for:

A. Flat passband.
B. Linear phase response.
C. Ripples in the passband but sharper roll-off than Butterworth.
D. Slowest roll-off.

40 In a Shunt m-derived T-section, the series arms consist of:

A. Single Inductors (for LPF)
B. Parallel LC circuits
C. Series LC circuits
D. Resistors

41 For a symmetrical -network, the characteristic impedance is:

A.
B.
C.
D.

42 What happens to the characteristic impedance of a Constant-K LPF at the cut-off frequency ?

A. It becomes infinite.
B. It becomes zero or imaginary.
C. It remains .
D. It becomes negative.

43 Which filter is characterized by the equation ?

A. Passive Low Pass Filter (RC)
B. Passive High Pass Filter (RC)
C. Active High Pass Filter
D. Inductive Filter

44 To convert a low-pass Constant-K filter prototype to a high-pass filter, one must:

A. Replace L with C and C with L.
B. Double the values of L and C.
C. Halve the values of L and C.
D. Add resistors in series.

45 In a composite filter design, the order of cascading sections is usually:

A. Constant K m-derived Constant K
B. Half-Section Constant K m-derived Half-Section
C. m-derived Half-Section
D. Random

46 If an active filter circuit oscillates, the most likely cause is:

A. Negative feedback is too high.
B. Positive feedback is present causing instability.
C. The input signal is too small.
D. The capacitors are too large.

47 The Bandwidth of a filter is defined as:

A.
B.
C.
D.

48 What is the formula for the design impedance in terms of L and C for a prototype filter?

A.
B.
C.
D.

49 In a First-Order Active HPF, if and , calculate the cut-off frequency.

A. 1.59 kHz
B. 15.9 kHz
C. 159 Hz
D. 1.59 Hz

50 Why is the Slew Rate of the Op-Amp important in Active Filter design?

A. It determines the DC gain.
B. It limits the maximum frequency and amplitude the filter can handle without distortion.
C. It determines the input impedance.
D. It sets the lower cut-off frequency.