Passive Filters — Engineering Board Exam Practice Questions

25 free engineering board exam reviewer questions on Passive Filters (AC Circuits), each with the correct answer and a worked solution.

  1. Two identical RC low-pass sections, each with a cutoff of 1 kHz, are cascaded with a buffer between them so that the sections do not load…
  2. A first-order RC high-pass filter delivers 3.5 V rms for a 10 V rms input at 500 Hz. What is its cutoff frequency?
  3. In the loaded low-pass filter shown, R1=1 k , R2=1.5 k (the load), and C=100 nF. Find the cutoff frequency.
  4. The band-stop (notch) filter shown has R=220, , L=25 mH, and C=400 nF. At what frequency is the output voltage (ideally) zero?
  5. A band-pass filter has half-power frequencies of 3 kHz and 12 kHz. Its center frequency, taken as the geometric mean, is
  6. A second-order passive low-pass filter (two reactive sections) rolls off at what rate beyond its cutoff frequency?
  7. A series resonant band-pass filter has a center frequency of 10 kHz and a quality factor of 25. What is its bandwidth?
  8. An RC low-pass filter is driven by a 10 V signal at ten times its cutoff frequency. Find the output voltage.
  9. A filter delivers 5 V at its output when 10 V is applied at its input. What is its voltage gain in decibels?
  10. A filter passes 10 W in its passband. How much power does it pass at the cutoff frequency?
  11. The series RLC band-pass filter shown takes its output across the resistor, with L=10 mH, C=100 nF, and R=100, . Find its bandwidth.
  12. The series RLC band-pass filter shown takes its output across the resistor, with L=10 mH, C=100 nF, and R=100, . Find its center frequency.
  13. The gain plot of a first-order RC low-pass filter is shown (the red dot marks the cutoff frequency). If a 3 V rms signal at 10 kHz is…
  14. The RL high-pass filter shown uses R=470, and L=22 mH. Find its cutoff frequency.
  15. The RL low-pass filter shown uses R=10 k and L=100 mH. Find its cutoff frequency.
  16. Find the voltage gain, in decibels, of the RC low-pass filter shown (R=330, , C=100 nF) at 24.1 kHz.
  17. For the RC low-pass filter shown (R=6.8 k , C=22 nF), by how many degrees does the output voltage lag the input voltage at 3.19 kHz?
  18. An RC high-pass filter with C=470 nF and R=680, is driven by a 10 V rms sine wave at 124 Hz. Find the rms output voltage.
  19. An RC low-pass filter with R=470, and C=1, F is driven by a 10 V rms sine wave at 677 Hz. Find the rms output voltage.
  20. A band-pass filter has lower and upper cutoff frequencies of 8 kHz and 12 kHz. What is its bandwidth?
  21. Beyond the cutoff frequency, the output of a first-order passive filter rolls off at
  22. At the cutoff frequency of a first-order filter, the output voltage is what fraction of the maximum (passband) output?
  23. A low-pass filter
  24. The RC high-pass filter shown uses R=4.7 k and C=22 nF. Find its cutoff frequency.
  25. The RC low-pass filter shown uses R=15 k and C=10 nF. Find its cutoff frequency.