Deck 19: Active Filters Key

Question 1

Passive filters are built with resistors,capacitors,and op amps.

Answer 1

False

Question 2

Why are some filters designed with a linear phase shift for the fundamental and all significant harmonics?

A) to prevent oscillations
B) to notch out certain frequencies
C) to cutoff at a desired frequency
D) to prevent distortion of digital signals

Answer 2

D

Question 3

Ac power line hum can be removed by using a properly designed Sallen-Key second-order notch filter.

Answer 3

True

Question 4

Predistortion refers to decreasing the design value of Q as needed to compensate for a limited gain-bandwidth product.

Question 5

Having voltage gain,center frequency,and bandwidth all independently tunable is a major advantage of which type filter?

A) Sallen-Key
B) Multiple-feedback
C) Biquadratic
D) State-variable

Question 6

A low-pass filter passes all frequencies from zero to the cutoff frequency and blocks all frequencies above the cutoff frequency.

Question 7

Monotonic means that the stopband has no ripples.

Question 8

If the damping factor is increased,the resonant peak increases.

Question 9

The bandstop filter is sometimes called a notch filter because it removes all frequencies in the stopband.

Question 10

An LC filter has an order of two because it contains two reactive components,an inductor and a capacitor.

Question 11

A filter that shifts the phase of the output signal without changing the magnitude is the

A) all-pass filter.
B) bandstop filter.
C) high-pass filter.
D) low-pass filter.

Question 12

The order of an active filter depends on the number of transistor circuits it contains.

Question 13

A filter passes one band of frequencies while rejecting another.

Question 14

If a rippled passband is acceptable,the Chebyshev and elliptic filters are the filters of choice.

Question 15

When used to compensate for the time delay of another filter,the all-pass filter is sometimes called a

A) compensator filter.
B) delay equalizer.
C) shift filter.
D) pass time filter.

Question 16

The bandwidth of a bandpass filter is the sum of its upper and lower 3-dB cutoff frequencies.

Question 17

With a constant input voltage,attenuation is the output voltage at any frequency divided by the output voltage in the midband.

Question 18

A high-order active filter can be built by cascading second-order stages whose resonant frequencies and Qs are staggered in precisely the right way to get the desired overall response.

Question 19

Cascading first and second order filters will not result in higher-order filters.

Question 20

The voltage gain of a Sallen-Key notch filter must be less than 2 in order to

A) remove undesired frequencies.
B) produce oscillations.
C) avoid oscillations.
D) amplify desired frequencies.

Question 21

Attenuation is almost always expressed in ________.

A) mhos
B) volts
C) joules
D) decibels

Question 22

A filter that has a passband and no stopband is the ________.

A) high-pass
B) bandpass
C) bandstop
D) all-pass

Question 23

Which filter provides flatness of the passband response,but has a relatively slow roll-off rate?

A) Butterworth
B) Chebyshev
C) Bessel
D) elliptic

Question 24

Which filter has high sensitivity but low complexity of design and operation?

A) TT
B) KHN
C) MFB
D) State-variable

Question 25

Which filter produces the least distortion of digital signals?

A) Butterworth
B) Chebyshev
C) Bessel
D) elliptic

Question 26

Circuits that separate desired signals from undesired signals,block interfering signals,and enhance speech and video are called ________.

A) amplifiers
B) attenuators
C) oscillators
D) filters

Question 27

Which filter is configured as a voltage-controlled voltage source filter?

A) Sallen-Key
B) Multiple-feedback
C) Biquadratic
D) State-variable

Question 28

Which of the following is not one of the five types of filters?

A) low-pass
B) medium-pass
C) bandstop
D) all-pass

Question 29

The highest frequency in the passband of a low-pass filter is called the

A) optimal frequency.
B) resonant frequency.
C) cutoff frequency.
D) pole frequency.

Question 30

If the Q of a bandpass filter is less than 1,it is called a

A) wideband filter.
B) narrowband filter.
C) notch filter.
D) low-pass filter.

Question 31

Which filter has a fast roll-off,but has ripples appear in the passband of the frequency response?

A) Butterworth
B) Chebyshev
C) Bessel
D) elliptic

Question 32

Which filter will always produce the least roll-off of all the approximations?

A) Butterworth
B) Chebyshev
C) Bessel
D) elliptic

Question 33

Which filter has the fastest possible roll-off in the transition region,but has a rippled passband and a rippled stopband?

A) Butterworth
B) Chebyshev
C) Bessel
D) elliptic

Question 34

Filters that are useful below 1 MHz,have power gain,and are relatively easy to tune are ________.

A) first-order
B) passive
C) active
D) notch

Question 35

Filters built with resistors,capacitors,and inductors are referred to as ________.

A) first-order
B) passive
C) active
D) notch

Question 36

Which filter offers the advantage of three simultaneous outputs: low-pass,high-pass,and bandpass?

A) Sallen-Key
B) Multiple-feedback
C) Butterworth
D) State-variable

Question 37

Which filter has as its passband all frequencies between the lower and upper cutoff frequencies?

A) low-pass
B) high-pass
C) bandpass
D) bandstop

Question 38

The graph of a filter's voltage gain versus its frequency is the filter's

A) amplification factor.
B) overall gain.
C) frequency response.
D) passband.

Question 39

A filter that blocks all frequencies from zero up to the cutoff frequency and passes all frequencies above the cutoff frequency is the

A) low-pass.
B) high-pass.
C) notch.
D) all-pass.

Question 40

Which of the following is not one of the five basic approximations?

A) Butterworth
B) Bessel
C) Twin-T
D) Elliptic

Question 41

With regard to filter performance,limited gain-bandwidth product of an op amp

A) increases the Q of a stage.
B) decreases the Q of a stage.
C) causes distortion.
D) reduces distortion.

Question 42

A first-order filter can implement only a Butterworth response because first-order stages have no

A) resonant frequency.
B) capacitors.
C) resistors.
D) active devices.

Question 43

Which order filter is most common because it is easy to build and analyze?

A) first
B) second
C) third
D) fourth

Question 44

A method used to correct for limited GBW is ________.

A) attenuation
B) damping
C) predistortion
D) multiple-feedback

Question 45

As a filter circuit's damping factor is increased,what happens to the resonant peak?

A) increases
B) decreases
C) remains unchanged
D) becomes distorted

Question 46

When filter stages are cascaded,how is the total decibel attenuation calculated?

A) decibel sum of each stage
B) decibel difference of each stage
C) multiply decibels of each stage
D) average decibel total

Question 47

A special frequency used in the design of active filters is the

A) resonant frequency.
B) cutoff frequency.
C) half-power point frequency.
D) pole frequency.

Question 48

A filter that consists of three cascaded second-order stages has an order of ________.

A) 2
B) 3
C) 5
D) 6

Question 49

How is all serious filter design accomplished?

A) by using computers
B) by hand
C) by trial and error
D) by contracting serious engineers

Question 50

In terms of damping,the Butterworth response is

A) critically damped.
B) underdamped.
C) overdamped.
D) not damped.