Deck 15: Active Filters

Question 1

Refer to the figure above. The low- pass filter with a 20 dB/decade roll- off is

A)a).
B)b).
C)c).
D)None of the above.

Answer 1

D

Question 2

Sallen- Key filters are also called

A)VCVS filters.
B)biquadratic filters.
C)state- variable filters.
D)multiple feedback filters.

Answer 2

A

Question 3

A low- pass filter has a cutoff frequency of 1.23 kHz. Determine the bandwidth of the filter.

A)644 Hz
B)2.46 kHz
C)1.23 kHz
D)Not enough information is given.

Answer 3

C

Question 4

A high- pass filter has R = 47 k▲ and C = 0.002 µF. The cutoff frequency is

A)10.6 kHz.
B)1.69 kHz.
C)3.39 Hz.
D)None of the above.

Question 5

Refer to the figure above. The cutoff frequency for the first filter section is the cutoff frequency for the second section.

A)higher than
B)lower than
C)equal to
D)None of the above.

Question 6

Refer to the figure above. Identify the high- pass filter with a 40 dB/decade roll- off.

A)a)
B)b)
C)c)
D)d)

Question 7

A band- stop filter is also known as

A)a notch filter.
B)a band- reject filter.
C)a band- elimination filter.
D)All of the above.

Question 8

The Q of a band- pass filter is

A)the ratio of the center frequency to the bandwidth.
B)the quiescent current specification of the op- amp input stage.
C)the difference between the two op- amp power supply voltages.
D)not related to the damping factor.

Question 9

A multiple- feedback band- pass filter

A)uses a minimum of two op- amps.
B)is used for a narrow band high Q)filter.
C)is also known as a Sallen- Key filter.
D)is used for a wide band low Q)filter.

Question 10

Refer to the figure above. This circuit is known as a and the roll- off rate is _.

A)high- pass filter, 20 dB/decade
B)band- pass filter, 80 dB/decade
C)low- pass filter, 60 dB/decade
D)high- pass filter, 80 dB/decade

Question 11

Which of the following is not an advantage of active filters over passive filters?

A)Active filters have a low output impedance.
B)Active filters provide filtering with gain.
C)Active filters require no power to operate.
D)Active filters have minimal loading due to a high input impedance.

Question 12

The state- variable filter

A)has a low- pass, high- pass and band- pass output.
B)uses fewer than three op- amps.
C)is difficult to tune.
D)has high component sensitivity.

Question 13

The type of filter response with a rippled passband is the

A)Inverse Chebyshev.
B)Butterworth.
C)Bessel.
D)Chebyshev.

Question 14

The filter response characteristic that distorts pulses the least is the

A)Chebyshev.
B)Bessel.
C)Elliptic.
D)Butterworth.

Question 15

A maximally flat frequency response is a common name for

A)Colpitts.
B)Butterworth.
C)Bessel.
D)Chebyshev.

Question 16

A single RC circuit produces a roll- off rate of

A)- 20 dB/decade.
B)- 6 dB/octave.
C)- 40 dB/decade.
D)A and B above.

Question 17

Refer to c)in the figure above. This is the frequency response curve for a

A)low- pass filter.
B)high- pass filter.
C)band- pass filter.
D)band- stop filter.

Question 18

A pole is a network that contains

A)a resistor and an inductor.
B)a resistor and a capacitor.
C)a capacitor and an inductor.
D)two resistors and one inductor.

Question 19

The filter with the slowest roll- off rate is the

A)Chebyshev.
B)Butterworth.
C)Elliptic.
D)Bessel.

Question 20

Refer to the figure above. Identify the active single- pole high- pass filter.

A)a)
B)b)
C)c)
D)d)

Question 21

The lowest frequency that an active low- pass filter can pass is

A)determined by the damping factor.
B)determined by the feedback capacitor value.
C)determined by the unity gain bandwidth of the op- amp.
D)0 Hz.

Question 22

If a Butterworth filter has 9 second- order stages, its rolloff rate is

A)180 dB per decade.
B)360 dB per decade.
C)20 dB per decade.
D)40 dB per decade.

Question 23

Low- Q filters are circuits, and high- Q filters are circuits.

A)wide band- pass, narrow band- pass
B)low order, high order
C)low pass, high pass
D)band- pass, band- stop

Question 24

Another name for a band- stop filter is an)filter.

A)all- pass
B)notch
C)all- stop
D)low- cut

Question 25

Above the cutoff frequency of a low- pass filter, the output voltage

A)does not change.
B)decreases.
C)increases.
D)doubles for every 1 kHz increase in frequency.

Question 26

Band- pass filters are designed to pass a band of frequencies between

A)1 kHz and 10 MHz.
B)fc1 and fc2.
C)1 kHz and 10 kHz.
D)a band- start and band- stop.

Question 27

What is the value of resistance needed with a 0.01 µF capacitor for a critical frequency of 23.4 kHz?

A)132.9 k▲
B)2.34 k▲
C)18 k▲
D)680 ▲

Question 28

Refer to the figure above. The low- pass filter with a roll- off of 40 dB/decade is

A)a).
B)b).
C)c).
D)d).

Question 29

A notch filter is an)

A)all- pass filter.
B)band- stop circuit.
C)band- pass circuit.
D)time- delay circuit.

Question 30

A low- pass filter with a roll- off rate of 60 dB/decade is needed. The best combination to use is

A)a 2- pole filter followed by another 2- pole.
B)a 2- pole filter followed by a 1- pole.
C)two single- pole filters in series.
D)None of the above.

Question 31

By cascading low- pass filters, can be improved.

A)roll- off rate
B)Q- rating
C)bandwidth
D)phase shift

Question 32

A high- pass active filter has a cutoff frequency of 1.23 kHz. The bandwidth of this filter is

A)1.23 kHz.
B)2.46 kHz.
C)644 Hz.
D)Cannot determine.

Question 33

The center frequency of a band- pass filter is always equal to the

A)bandwidth divided by Q.
B)3- dB frequency.
C)bandwidth.
D)geometric average of the cutoff frequencies.

Question 34

The damping factor DF)of an active filter determined by

A)the number of poles.
B)the negative feedback of the circuit.
C)the Q of the circuit.
D)the positive feedback of the circuit.