Deck 15: Active Filters

Question 1

Figure 4 A test of a filter using an oscilloscope
Refer to Figure 4. The signal on the X channel of the oscilloscope is a(n)

A)sawtooth
B)continuous frequency sinusoidal wave
C)amplitude modulated frequency
D)constant amplitude swept frequency

Answer 1

A

Question 2

The critical frequency of a high- pass filter is where the response is

A)-20 dB from the passband response
B)at its highest point
C)-3 dB from the passband response
D)-6 dB from the passband response

Answer 2

C

Question 3

A high Q bandpass filter

A)can reject a specific frequency
B)has a narrow bandwidth
C)is usually constructed from cascaded low- pass and high- pass filters
D)all of the above

Answer 3

B

Question 4

Figure 1 Stage 1: DF = 1.848 and R₁/R₂ = 0.152; stage 2: DF = 0.765 and R₃/R₄ =1.235.
Refer to Figure 1 with values as given. R3 should have a value of

A)1.8 k▲
B)1.5 k▲
C)1.2 k▲
D)none of the above

Question 5

The biquad filter has

A)a summing amplifier, an inverting amplifier, and an integrator
B)an inverting amplifier and two differentiators
C)a summing amplifier and two differentiators
D)an inverting amplifier and two integrators

Question 6

Figure 1 Stage 1: DF = 1.848 and R₁/R₂ = 0.152; stage 2: DF = 0.765 and R₃/R₄ =1.235.
Refer to Figure 1 with values as given. R1 should have a value of

A)1.2 k▲
B)1.8 k▲
C)1.5 k▲
D)none of the above

Question 7

Figure 5 Response curve for three different filters
Refer to Figure 5. The response labeled "A" represents a

A)Butterworth response
B)Bessel response
C)Chebyshev response
D)none of the above

Question 8

A low- pass filter has a critical frequency of 10 kHz. The bandpass is

A)20 kHz
B)5.0 kHz
C)15 kHz
D)10 kHz

Question 9

Figure 5 Response curve for three different filters
Refer to Figure 5. The response labeled "B" represents a

A)Butterworth response
B)Bessel response
C)Chebyshev response
D)none of the above

Question 10

Figure 2 Note that the capacitors have different values.
Refer to Figure 2. The fc for the first section is

A)800 Hz
B)160 Hz
C)80 Hz
D)1.6 kHz

Question 11

Figure 3
Refer to Figure 3. This type of filter is called a

A)biquad filter
B)Sallen- Key filter
C)multiple- feedback filter
D)state- variable filter

Question 12

The bandwidth of a bandpass filter is measured at

A)the -2 dB frequencies
B)the -6 dB frequencies
C)the -4 dB frequencies
D)none of the above

Question 13

The best response to use for pulses is

A)Butterworth response
B)Bessel response
C)Chebyshev response
D)none of the above

Question 14

A basic one- pole RC low- pass filter has fc = 5.9 kHz using a 0.01 µF capacitor. The resistor value is

A)2.7 k▲
B)1.6 k▲
C)16 k▲
D)270 ▲

Question 15

Figure 1 Stage 1: DF = 1.848 and R₁/R₂ = 0.152; stage 2: DF = 0.765 and R₃/R₄ =1.235.
Refer to Figure 1. Assume Vin = 1.0 Vpp sine wave at 20 kHz. At this frequency, Vout is approximately

A)1.0 Vpp
B)10 mVpp
C)1.0 mVpp
D)100 µVpp

Question 16

Figure 2 Note that the capacitors have different values.
Refer to Figure 2. Assume the capacitors in section 1 are made larger. This change will

A)decrease the bandwidth
B)increase the bandwidth
C)not affect the bandwidth

Question 17

Figure 4 A test of a filter using an oscilloscope
Refer to Figure 4. The block with the ? on it represents a

A)low- pass filter
B)impedance matching circuit
C)detector
D)amplifier

Question 18

Figure 3
Refer to Figure 3. An advantage of this type of filter is that it

A)the low and high- pass outputs are equivalent to a 4- pole filter
B)can be optimized for all three outputs
C)the bandpass output can have a very high Q
D)all of the above

Question 19

Assume a high- pass filter and a low- pass filter are cascaded to form a band- pass filter. The upper cutoff frequency will be determined by

A)the high- pass filter
B)answer depends on the order of the filters
C)the low- pass filter
D)none of the above

Question 20

Figure 4 A test of a filter using an oscilloscope
Refer to Figure 4. The input signal to the filter (Vin)is a(n)

A)continuous frequency sinusoidal wave
B)amplitude modulated frequency
C)constant amplitude swept frequency
D)sawtooth

Question 21

Figure 1 Stage 1: DF = 1.848 and R₁/R₂ = 0.152; stage 2: DF = 0.765 and R₃/R₄ =1.235.
Refer to Figure 1. The type of filter is a

A)low- pass Sallen- Key filter
B)high- pass Sallen- Key filter
C)low- pass biquad filter
D)high- pass biquad filter

Question 22

Figure 1 Stage 1: DF = 1.848 and R₁/R₂ = 0.152; stage 2: DF = 0.765 and R₃/R₄ =1.235.
Refer to Figure 1. The ideal roll- off rate is

A)-120 dB/decade
B)-80 dB/decade
C)-40 dB/decade
D)-20 dB/decade

Question 23

The damping factor, DF, is determined by the number of poles in a filter.

Question 24

Figure 3
Refer to Figure 3. The last stage is

A)a differentiator
B)an inverting amp
C)an integrator
D)a summing amplifier

Question 25

A basic RC (one R, oneC)filter has a -20dB/decade roll- off.

Question 26

Figure 4 A test of a filter using an oscilloscope
Refer to Figure 4. The oscilloscope needs to

A)generate an internal time base
B)use normal triggering
C)use external triggering
D)be in X- Y mode

Question 27

Figure 2 Note that the capacitors have different values.
Refer to Figure 2. The circuit is a

A)high- pass filter
B)low- pass filter
C)notch filter
D)bandpass filter

Question 28

A single- pole filter cannot be used as a notch filter.

Question 29

The Q of a band- pass filter is inversely proportional to the damping factor.

Question 30

Figure 2 Note that the capacitors have different values.
Refer to Figure 2. Assume section 1 and section 2 are exchanged. This will

A)change the overall response
B)change the type of filter
C)both A and B
D)neither A nor B

Question 31

The Chebyshev filter is noted for its flat response in the passband.

Question 32

Figure 2 Note that the capacitors have different values.
Refer to Figure 2. The fc for the second section is

A)1.6 kHz
B)800 Hz
C)80 Hz
D)160 Hz

Question 33

A biquad filter has both low- pass and high- pass outputs.

Question 34

The damping factor, DF, affects an active filter's response characteristics.

Question 35

The bandwidth of a basic band- pass filter is measured between the center frequency and a critical frequency.