Deck 14: Frequency Effects

Question 1

In the label dBm,the m at the end of dBm designates the millivolt reference.

Answer 1

False

Question 2

To prevent oscillations,most op amp circuits include an RC lag circuit that rolls off the voltage gain.

Answer 2

True

Question 3

A fast and simple method to test the frequency response of an amplifier is

A) by using sine-wave testing.
B) by using square-wave testing.
C) by measuring dc voltages.
D) by measuring resistance values.

Answer 3

B

Question 4

A common-emitter amplifier that uses coupling and bypass capacitors is an example of a dc amplifier.

Question 5

Impedance matching in communication systems is used because it produces maximum power transfer.

Question 6

Each time the ordinary power gain decreases by a factor of 2,the decibel power gain decreases by 3 dB.

Question 7

The frequency response of an ac amplifier shows decreased voltage gain at low frequencies because of the effects of capacitive reactances.

Question 8

In a dc amplifier,all the frequencies from zero up to the cutoff frequency is referred to as the

A) roll off.
B) maximum band.
C) notch frequencies.
D) bandwidth.

Question 9

The frequencies at which the voltage gain equals 0.707 of its maximum value are called the half-power frequencies.

Question 10

A designer can use direct coupling between amplifier stages in order to amplify down to zero hertz.

Question 11

A Bode plot is a graph that uses decibels and provides more information about the amplifier's response outside the midband.

Question 12

In music,the word octave refers to eight times the frequency.

Question 13

The frequency response of an amplifier is the graph of its gain versus the frequency.

Question 14

The Miller effect has useful applications because

A) it creates virtual capacitors that are much larger than the feedback capacitor.
B) it creates virtual resistors that are much larger than the load resistor.
C) it creates additional gain without adding amplifiers.
D) it makes coupling capacitors appear smaller than they actually are.

Question 15

When an op amp includes one dominant bypass capacitor that rolls off the voltage gain at a rate of 20 dB per decade,it means the op amp is

A) operating as an open-loop.
B) externally compensated.
C) internally compensated.
D) operating as a closed-loop.

Question 16

The total voltage gain of a two-stage cascaded amplifier is the sum of the individual voltage gains.

Question 17

The charging and discharging of a capacitor produce a lag in the output voltage of an RC bypass circuit.

Question 18

Most amplifiers are now being built using

A) BJTs.
B) MOSFETs.
C) power amps.
D) op amps.

Question 19

Decibel power gain is often used on data sheets to specify the power gain of devices.

Question 20

The total decibel voltage gain of two cascaded stages equals the sum of the individual decibel voltage gains.

Question 21

The frequencies at which the voltage gain equals 0.707 of its maximum value are called the

A) tuned RF frequencies.
B) full-power frequencies.
C) cutoff frequencies.
D) midband frequencies.

Question 22

The total decibel voltage gain of two cascaded stages equals the

A) decibel voltage gain of the individual stage.
B) sum of the individual decibel voltage gains.
C) product of the individual decibel voltage gains.
D) difference of the decibel voltage gains.

Question 23

What is one method used to reduce high frequency loss in amplifiers?

A) use large coupling capacitors
B) increase lengths of wires used between stages
C) use transformer coupling
D) keep wires as short as possible

Question 24

What is a dc amplifier that has high voltage gain,high input impedance,and low output impedance?

A) BJT
B) MOSFET
C) op amp
D) JFET

Question 25

Stray capacitance and inductance become serious considerations for discrete and IC devices that are operating

A) below 100 kHz.
B) above 100 kHz.
C) above 100 Hz.
D) below 100 Hz.

Question 26

When decibels are used to indicate the power level above 1 mW,what is the accepted label used?

A) dBV
B) dBm
C) VdB
D) mWdB

Question 27

What type amplifier uses direct coupling and amplifies signals down to 0 Hz?

A) transformer coupled amplifier
B) dc amplifier
C) ac amplifier
D) impedance coupled amplifier

Question 28

At high frequencies,the voltage gain of an ac amplifier decreases because of

A) low supply voltages.
C) large filter capacitors.
D) direct coupling design.
D) stray-wiring capacitance.

Question 29

The total voltage gain of a two-stage cascaded amplifier is the

A) voltage gain of the individual stage.
B) sum of the individual voltage gains.
C) product of the individual voltage gains.
D) difference of the voltage gains.

Question 30

A type of graph that uses decibels and provides more information about the amplifier's response outside the midband is the

A) response curve.
B) decibel curve.
C) frequency plot.
D) Bode plot.

Question 31

What type of scale compresses very large values and allows many decades to be seen?

A) linear
B) logarithmic
C) nonlinear
D) algebraic

Question 32

When decibels are used to indicate the voltage level above 1 V,what is the accepted label used?

A) dBV
B) dBm
C) VdB
D) mWdB

Question 33

Each time the ordinary power gain increases by a factor of 10,the decibel power gain increases by ________.

A) 1 dB
B) 5 dB
C) 10 dB
D) 20 db

Question 34

In music,the doubling of the frequency is referred to as ________.

A) doublet
B) quadruplet
C) octave
D) decade

Question 35

Ac amplifier voltage gain decreases at low frequencies because

A) coupling and bypass capacitive reactances increase.
B) coupling and bypass capacitive reactances decrease.
C) coupling and bypass capacitors act like short circuits.
D) direct coupling is used.

Question 36

A graph of an amplifier's gain versus its frequency is referred to as the amplifier's

A) frequency response.
B) roll off frequency.
C) half-power points.
D) cutoff frequencies.

Question 37

Sources of stray capacitance or inductance of conventional feed-through components does not include

A) geometry and internal structure of the device.
B) printed-circuit layout.
C) power supply voltage.
D) external leads on the device.

Question 38

In many communication systems maximum power transfer is produced by proper

A) impedance matching.
B) impedance coupling.
C) use of small signal amplifiers.
D) use of grounding.

Question 39

A reason for using decibel power gain is

A) that logarithms compress numbers.
B) that logarithms expand numbers.
C) that a decibel equals a watt.
D) that a decibel is 10 times larger than a logarithm.

Question 40

Each time the voltage gain decreases by a factor of 2,the decibel voltage gain

A) increases by 6 dB.
B) decreases by 6 dB.
C) increases by 10 dB.
D) decreases by 10 dB.

Question 41

An entry on a data sheet that lists the frequency limitation of an op amp is the

A) unity-gain frequency.
B) reverse breakover frequency.
C) cutoff frequency.
D) notch frequency.

Question 42

Instead of the term cutoff frequency,many technicians use the term

A) corner frequency.
B) edge frequency.
C) notch frequency.
D) resonant frequency.

Question 43

If an amplifier has a voltage gain of 100,000,it has a decibel voltage gain of ________.

A) 1 dB
B) 10 dB
C) 20 dB
D) 100 dB

Question 44

What produces a lag in the output voltage of an RC bypass circuit?

A) charging of a capacitor
B) discharging of a capacitor
C) charging and discharging of a capacitor
D) value of the supply voltage

Question 45

A FET's low frequency cutoff point is largely determined by

A) the value of the load resistor.
B) input and output coupling circuits.
C) the supply voltage.
D) stray wiring capacitance.

Question 46

What is the fastest and most accurate way to analyze the frequency response of a discrete BJT or FET amplifier?

A) use Multisim or other circuit simulation software
B) use square wave testing
C) use sine wave injection and oscilloscope signal tracing
D) use frequency generator injection and frequency counter testing

Question 47

What type of graph paper has a linear scale on the vertical axis and a logarithmic scale on the horizontal axis?

A) semi-linear
B) semi-logarithmic
C) semi-scalar
D) semi-algebraic

Question 48

If stage one of a cascaded amplifier system has a decibel voltage gain of 30 and stage two has a decibel voltage gain of 40,what is the total decibel voltage gain?

A) 30
B) 40
C) 70
D) 1200

Question 49

A graph of decibel voltage gain versus frequency as it would appear on semilogarithmic paper is called

A) a frequency response.
B) Fourier's analysis.
C) a Bode plot.
D) a Miller plot.

Question 50

What type of circuit rolls off voltage gain and prevents an op amp from oscillating?

A) attenuator
B) RC lead
C) RC lag
D) LC lag