CHAPTER 27 REVIEW QUESTIONS
1. The most accurate description of a system is
a. any collection of multiple electronic components.
b. a group of electronic components, circuits, or devices that collectively perform a useful function.
c. a piece of electronic equipment.
d. large complex interconnections of electronic
equipment.
2. Most electronic circuits
a. are in integrated circuit form.
b. are collections of discrete components wired
together.
c. contain at least one transistor.
d. are designed by a technician.
3. Which of the following is not involved in troubleshooting and repair of modern electronic equipment?
a. Finding and replacing the bad component.
b. Replacing a bad IC.
c. Replacing a defective board or module.
d. Discarding the bad device and replacing it with a
new one.
4. The primary work of a technician is
a. designing electronic circuits.
b. analyzing electronic circuits.
c. troubleshooting, testing, and repairing.
d. breadboarding prototypes.
5. Modern technicians work mostly with
a. schematic diagrams.
b. block diagrams.
6. An MP3 music player can be considered as a system.
a. True.
b. False.
7. Which of the following is not a linear circuit?
a. Amplifier.
b. Oscillator.
c. Power supply.
d. Flash memory.
8. The most common linear circuit is the
a. amplifier.
b. oscillator.
c. rectifier.
d. regulator.
9. Another name for a large-signal amplifier is
a. op amp.
b. RF amplifier.
c. dc amplifier.
d. power amplifier.
10. Most amplifiers are classified by
a. power level.
b. voltage level.
c. frequency range.
d. input impedance.
11. The name of a general-purpose dc differential amplifier that can be easily configured is the
a. power amplifier.
b. operational amplifier.
c. microwave amplifier.
d. small signal amplifier.
12. A circuit that generates a sine-wave or rectangularwave signal is called a(n)
a. oscillator.
b. amplifier.
c. rectifier.
d. filter.
13. Which of the following is not a method of setting the
frequency of an oscillator?
a. Resistor-capacitor combination.
b. Capacitor-inductor combination.
c. Quartz crystal.
d. Transformer
14. A circuit that generates a precise frequency that can
be changed in increments is called a(n)
a. amplifier.
b. oscillator.
c. frequency synthesizer.
d. VCO.
15. The power supply circuit that converts ac into dc is
the
a. regulator.
b. transformer.
c. filter.
d. rectifier.
16. A power supply circuit that maintains a constant dc
output voltage is called a
a. rectifier.
b. regulator.
c. filter.
d. dc-dc converter.
17. A power supply circuit that converts dc into ac is
known as a(n)
a. rectifier.
b. dc-dc converter.
c. inverter.
d. filter.
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18. Digital circuits process which type of signals?
a. Analog.
b. Binary.
c. RAM.
d. Nonvolatile memory.
19. The basic building blocks of all digital circuits are
a. resistors and capacitors.
b. counters and registers.
c. gates and flip-flops.
d. diodes and transistors.
28. A circuit that selects one digital input from memory
and routes it to an output is a
a. differential amplifier.
b. multiplexer.
c. decoder.
d. demultiplexer.
20. A circuit that generates a binary 1 only when all inputs are binary 1 is the
a. AND gate.
b. OR gate.
c. inverter.
d. NAND gate.
29. What electronic circuit is found in almost every electronic product?
a. Microcontroller.
b. FPGA.
c. PLL.
d. DAC.
21. A circuit that store one bit of information is called a(n)
a. AND gate.
b. exclusive OR gate.
c. inverter.
d. flip-flop.
30. An FPGA is a digital circuit that
a. is the same as a microcontroller.
b. incorporates a PLL frequency synthesizer.
c. contains multiple functional digital circuits.
d. can be programmed to implement any digital
function.
22. A circuit that stores one complete binary number is
called a
a. NAND gate.
b. multiplexer.
c. decoder.
d. register.
31. The circuit used to digitize an analog signal is a(n)
a. analog-to-digital converter.
b. digital-to-analog converter.
c. comparator.
d. a hybrid circuit.
23. A circuit that digitizes an analog signal is called a(n)
a. analog-to-digital converter.
b. digital-to-analog converter.
c. comparator.
d. counter.
32. The output is an ADC is
a. an analog signal.
b. a sequence of binary numbers.
c. either high or low.
d. a single binary number.
24. A complete digital computer on a chip is called a(n)
a. microcomputer.
b. microcontroller.
c. embedded controller.
d. all of the above.
33. The circuit that reconstructs an analog signal from
binary words stored in a memory is a(n)
a. analog-to-digital converter.
b. digital-to-analog converter.
c. comparator.
d. a hybrid circuit.
25. Which of the following is not a part of a microcontroller?
a. Memory.
b. Power supply.
c. CPU.
d. Input/output circuits.
26. Which electronic component can be used as a memory circuit?
a. Capacitor.
b. Resistor.
c. Inductor.
d. Transformer.
27. Which type of memory loses its stored data if power
is removed?
a. ROM.
b. Flash.
484
34. The output of a comparator is
a. an analog signal.
b. a sequence of binary numbers.
c. either high or low.
d. a single binary number.
35. Which of the following would not be considered as an
electronic system?
a. Garage door opener.
b. TV set.
c. Filter.
d. Traffic light controller.
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CHAPTER 27 PROBLEMS
SECTION 27.3 Linear, or Analog, Circuits
27.1 An amplifier has an input of 40 mV and an output
of 2 V. What is the gain?
27.2 An amplifier has an output power of 50 W and a
gain of 800. What is the input power?
27.3
Express the voltage gain of 300 in dB.
27.4
Express the power gain of 75 in dB.
SECTION 27.6 System Examples
27.6 Draw a basic block diagram representing any
system of your choice.
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CHAPTER 35 REVIEW QUESTIONS
1. Which of the following is not a characteristic of an
ideal op amp?
a. Infinite gain.
b. Infinite input impedance.
c. Infinite output impedance.
d. Zero output impedance.
2. The ground pin on a 741 op amp is
a. pin 3.
b. pin 4.
c. pin 5.
d. none of the above.
3. At the unity-gain frequency, the open-loop voltage
gain is
a. 1.
b. Av(mid).
c. Zero.
d. Very large.
4. The cutoff frequency of an op amp equals the unitygain frequency divided by
a. the cutoff frequency.
b. closed-loop voltage gain.
c. unity.
d. common-mode voltage gain.
5. If the cutoff frequency is 20 Hz and the midband
open-loop voltage gain is 1,000,000, the unity-gain
frequency is
a. 20 Hz.
b. 1 MHz.
c. 2 MHz.
d. 20 MHz.
6. If the unity-gain frequency is 5 MHz and the
midband open-loop voltage gain is 100,000, the
cutoff frequency is
a. 50 Hz.
b. 1 MHz.
c. 1.5 MHz.
d. 15 MHz.
7. The initial slope of a sine wave is directly
proportional to
a. slew rate.
b. frequency.
c. voltage gain.
d. capacitance.
8. When the initial slope of a sine wave is greater than
the slew rate,
a. distortion occurs.
b. linear operation occurs.
c. voltage gain is maximum.
d. the op amp works best.
9. The power bandwidth increases when
a. frequency decreases.
b. peak value decreases.
c. initial slope decreases.
d. voltage gain increases.
10. A 741C contains
a. BJTs.
b. FETs.
c. MOSFETs.
d. all of the above.
11. A 741C amplifier does not work with
a. dc.
b. ac.
c. both a and b.
d. digital.
12. The input impedance of a BIFET op amp is
a. low.
b. medium.
c. high.
d. extremely high.
13. An TL081 is a
a. diff amp.
b. source follower.
c. Bipolar op amp.
d. BIFET op amp.
14. If the two supply voltages are
of an op amp is closest to
a. 0 V.
b. 12 V.
c. 12 V.
d. 24 V.
12 V, the MPP value
15. The open-loop cutoff frequency of a 741C is controlled by
a. a coupling capacitor.
b. the output short circuit current.
c. the power bandwidth.
d. a compensating capacitor.
16. The 741C has a unity-gain frequency of
a. 10 Hz.
b. 20 kHz.
c. 1 MHz.
d. 15 MHz.
17. The unity-gain frequency equals the product of
closed-loop voltage gain and the
a. compensating capacitance.
b. tail current.
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c. closed-loop cutoff frequency.
d. load resistance.
18. If funity is 10 MHz and midband open-loop voltage
gain is 200,000, then the open-loop cutoff frequency
of the op amp is
a. 10 Hz.
b. 20 Hz.
c. 50 Hz.
d. 100 Hz.
19. The initial slope of a sine wave increases when
a. frequency decreases.
b. peak value increases.
c. Cc increases.
d. slew rate decreases.
20. If the frequency of the input signal is greater than the
power bandwidth,
a. slew-rate distortion occurs.
b. a normal output signal occurs.
c. output offset voltage increases.
d. distortion may occur.
21. An op amp has an open input. The output voltage
will be
a. zero.
b. slightly different from zero.
c. maximum positive or negative.
d. an amplified sine wave.
22. An op amp has a voltage gain of 200,000. If the
output voltage is 1 V, the input voltage is
a. 2 ␮V.
b. 5 ␮V.
c. 10 mV.
d. 1 V.
23. A 741C has supply voltages of 15 V. If the
load resistance is large, the MPP value is
approximately
a. 0 V.
b. 15 V.
c. 27 V.
d. 30 V.
24. Above the cutoff frequency, the voltage gain of a 741C
decreases approximately
a. 10 dB per decade.
b. 20 dB per octave.
c. 10 dB per octave.
d. 20 dB per decade.
25. The voltage gain of an op amp is unity at the
a. cutoff frequency.
b. unity-gain frequency.
c. generator frequency.
d. power bandwidth.
662
26. When slew-rate distortion of a sine wave occurs, the
output
a. is larger.
b. appears triangular.
c. is normal.
d. has no offset.
27. A 741C has
a. a voltage gain of 100,000.
b. an input impedance of 2 M.
c. an output impedance of 75 .
d. all of the above.
28. The closed-loop voltage gain of an inverting amplifier
equals
a. the ratio of the input resistance to the feedback
resistance.
b. the open-loop voltage gain.
c. the feedback resistance divided by the input resistance.
d. the input resistance.
29. The noninverting amplifier has a
a. large closed-loop voltage gain.
b. small open-loop voltage gain.
c. large closed-loop input impedance.
d. large closed-loop output impedance.
30. The voltage follower has a
a. closed-loop voltage gain of unity.
b. small open-loop voltage gain.
c. closed-loop bandwidth of zero.
d. large closed-loop output impedance.
31. A summing amplifier can have
a. no more than two input signals.
b. two or more input signals.
c. a closed-loop input impedance of infinity.
d. a small open-loop voltage gain.
32. An instrumentation amplifier has a high
a. output impedance.
b. power gain.
c. CMRR.
d. supply voltage.
33. In a differential amplifier, the CMRR is limited
mostly by the
a. CMRR of the op amp.
b. gain-bandwidth product.
c. supply voltages.
d. tolerance of the resistors.
34. The input signal for an instrumentation amplifier
usually comes from
a. an inverting amplifier.
b. a resistor.
c. a differential amplifier.
d. a Wheatstone bridge.
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35. In the classic three op-amp instrumentation amplifier,
the differential voltage gain is usually produced by the
a. first stage.
b. second stage.
c. mismatched resistors.
d. output op amp.
36. Another name for a summable amplifier is
a. follower.
b. mixer.
c. instrumentation amp.
d. modulator.
37. An input transducer converts
a. voltage to current.
b. current to voltage.
c. an electrical quantity to a nonelectrical quantity.
d. a nonelectrical quantity to an electrical quantity.
38. A thermistor converts
a. light to resistance.
b. temperature to resistance.
c. voltage to sound.
d. current to voltage.
39. When we trim a resistor, we are
a. making a fine adjustment.
b. reducing its value.
c. increasing its value.
d. making a coarse adjustment.
40. If an op amp has only a positive supply voltage, its
output cannot
a. be negative.
b. be zero.
c. equal the supply voltage.
d. be ac-coupled.
CHAPTER 35 PROBLEMS
SECTION 35.2 The 741 Op Amp
35.1 Assume that negative saturation occurs at 1 V less
than the supply voltage with an 741C. How much
inverting input voltage does it take to drive the op
amp of Fig. 35-32 into negative saturation?
–
v2
35.5 An op amp has a slew rate of 70 Vy␮s. What is the
power bandwidth for a peak output voltage of 7 V?
SECTION 35.3 The Inverting Amplifier
35.6 What are closed-loop voltage gain and bandwidth in
Fig. 35-33? What is the output voltage at 1 kHz? At
10 MHz? Draw the ideal Bode plot of closed-loop
voltage gain.
+18 V
+
35.4 The input voltage to an op amp is a large voltage
step. The output is an exponential waveform that
changes 2.0 V in 0.4 ␮s. What is the slew rate of the
op amp?
741C
vout
–
+
1.8 kΩ
10 kΩ
180 Ω
–18 V
Figure 35-32
–
25 mV
p-p
TL081A
vout
+
35.2 What is the common-mode rejection ratio of an
TL081A at low frequencies? Convert this decibel
value to an ordinary number. (See Table 35-1.)
Figure 35-33
35.3 What is the open-loop voltage gain of an 741A
when the input frequency is 1 kHz? 10 kHz? 100
kHz? (Assume a first-order response, that is, 20 dB
per decade rolloff.)
SECTION 35.4 The Noninverting Amplifier
35.7 In Fig. 35-34, what are the closed-loop voltage gain
and bandwidth? The ac output voltage at 100 kHz?
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+15 V
SECTION 35.7 Differential Amplifiers
35.10 The differential amplifier of Fig. 35-24 has R1 1.5 k and R2 30 k. What is the differential
voltage gain?
35.11 In Fig. 35-25, R1 1 k and R2 20 k. What is
the differential voltage gain?
35.12 In the Wheatstone bridge of Fig. 35-26, R1 10 k,
R2 20 k, R3 20 k, and R4 10 k. Is the
bridge balanced?
35.13 In the typical application of Fig. 35-27, transducer
resistance changes to 985 . What is the final output voltage?
+
25 mV
p-p
vout
–
3 kΩ
–15 V
150 Ω
Figure 35-34
SECTION 35.8 Instrumentation Amplifiers
35.14 In the instrumentation amplifier of Fig. 35-28, R1 1 k and R2 99 k. What is the output voltage if
vin 2 mV?
35.15 The value of RG is changed to 1008 in Fig. 35-29.
What is the differential output voltage if the differential input voltage is 20 mV?
SECTION 35.5 Common Op-Amp Applications
35.8 In Fig. 35-35a, what is the ac output voltage?
35.9 What is the output voltage in Fig. 35-35b? The
bandwidth?
40 kΩ
50 mVp-p
90 mVp-p
160 mVp-p
10 kΩ
+18 V
20 kΩ
–
40 kΩ
vout
LF157A
+
–18 V
(a)
+12 V
1 MΩ
+
50 mV
p-p
741C
–
vout
2Ω
–12 V
(b)
Figure 35-35
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At the monitoring station, the digital data are recovered
usually in an Ethernet switch that determines which camera
output will be selected for display or recording. It is then decompressed and connected to video monitors. The data are
also stored digitally in compressed form on hard disk drives.
These may be in a dedicated video unit on in a special server
computer designated for video storage. Some digital systems
can also accept inputs from analog cameras. The analog video
is digitized and compressed and either stored or displayed.
Digital systems can have much higher resolution. There
are multiple video standards used. Lower-resolution systems
use the common intermediate format (CIF), which has a
resolution of 352- by 288-pixel format at 30 fps. For higher
resolution, formats similar to standard digital TV with
resolutions of 480 lines (standard) or 720 lines and even
1080 lines for high definition.
The most advanced surveillance systems use special
software called video analytics. The software uses artificial
intelligence and machine vision algorithms to process the
video scenes. It can look for motion, recognize objects, and
do facial identification. In these advanced systems, little or
no human monitoring is needed.
CHAPTER 36 REVIEW QUESTIONS
1. To detect when the input is greater than a particular
value, use a
a. comparator.
b. clamper.
c. limiter.
d. relaxation oscillator.
2. The voltage out of a Schmitt trigger is
a. a low voltage.
b. a high voltage.
c. either a low or a high voltage.
d. a sine wave.
3. Hysteresis prevents false triggering associated with
a. a sinusoidal input.
b. noise voltages.
c. stray capacitances.
d. trip points.
4. If the input is a rectangular pulse, the output of an
integrator is a
a. sine wave.
b. square wave.
c. ramp.
d. rectangular pulse.
5. When a large sine wave drives a Schmitt trigger, the
output is a
a. rectangular wave.
b. triangular wave.
c. rectified sine wave.
d. series of ramps.
6. If pulse width decreases and the period stays the
same, the duty cycle
a. decreases.
b. stays the same.
688
c. increases.
d. is zero.
7. The output of a relaxation oscillator is a
a. sine wave.
b. square wave.
c. ramp.
d. spike.
8. If AVOL 5 100,000, the closed-loop knee voltage of a
silicon diode is
a. 1 V.
b. 3.5 V.
c. 7 V.
d. 14 V.
9. The input to a positive limiter is a triangular wave
with a peak-to-peak value of 8 V and an average
value of 0. If the reference level is 2 V, the output has
a peak-to-peak value of
a. 0 V.
b. 2 V.
c. 6 V.
d. 8 V.
10. A comparator with a trip point of zero is sometimes
called a
a. threshold detector.
b. zero-crossing detector.
c. positive limit detector.
d. half-wave detector.
11. To work properly, many IC comparators need an
external
a. compensating capacitor.
b. pullup resistor.
c. bypass circuit.
d. output stage.
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Class H Amplifiers
A class H amplifier extends the concept of class G by making the power supplies continuously variable. By making the
supply voltages tracking only a few volts above the peak outputs, efficiency is maximized at all signal levels. To do this,
the input signal needs to modulate the power supplies, making them continuously variable. This arrangement is shown
in the block diagram of Fig. S37-2.
Note: Class G and H amplifiers are more efficient that
standard class AB amplifiers but not as efficient as a class
D switching amplifier. However, the compromise is a good
one, and the filtering needs and noise of the class D amplifier
are eliminated.
Modulation
control
Positive dc
supply
Class AB
amplifier
+V
Speaker
Input
–V
Modulation
control
Negative dc
supply
Figure S37-2
A class H amplifier.
CHAPTER 37 REVIEW QUESTIONS
1. For class B operation, the collector or drain current
flows for
a. the whole cycle.
b. half the cycle.
c. less than half a cycle.
d. less than a quarter of a cycle.
2. Power amplifiers not used in which of the following?
a. Small-signal amplification.
b. Speaker drivers.
c. Motor drivers.
d. Transmitter amplifiers.
3. An audio amplifier operates in the frequency range of
a. 0 to 20 Hz.
b. 20 Hz to 2 kHz.
c. 20 to 20 kHz.
d. Above 20 kHz.
4. A tuned RF amplifier is
a. narrowband.
b. wideband.
c. direct-coupled.
d. a dc amplifier.
5. The first stage of a preamp is
a. a tuned RF stage.
b. large signal.
c. small signal.
d. a dc amplifier.
6. An inductor in the collector or drain lead of a class A
amplifier is used to
a. reduce distortion.
b. double output power.
c. improve efficiency.
d. reduce power consumption.
7. An emitter or source follower is a power amplifier
because it
a. has a high voltage gain.
b. can sustain higher dc supply voltages.
c. has a high input impedance and low output
impedance.
d. uses transistors with higher gains.
8. The most common name for a class AB amplifier
with no transformers is
a. emitter-follower amplifier.
b. class B amplifier.
c. diode-biased amplifier.
d. complementary symmetry amplifier.
9. Push-pull is almost always used with
a. class A.
b. class B.
c. class C.
d. all of the above.
10. One advantage of a class B push-pull amplifier is
a. no quiescent current drain.
b. maximum efficiency of 78.5%.
c. greater efficiency than class A.
d. all of the above.
11. Class C amplifiers are almost always
a. transformer-coupled between stages.
b. operated at audio frequencies.
c. tuned RF amplifiers.
d. wideband.
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12. The input signal of a class C amplifier
a. is negatively clamped at the base.
b. is amplified and inverted.
c. produces brief pulses of collector current.
d. all of the above.
13. The collector current of a class C amplifier
a. is an amplified version of the input voltage.
b. has harmonics.
c. is negatively clamped.
d. flows for half a cycle.
14. The bandwidth of a class C amplifier decreases when
the
a. resonant frequency increases.
b. Q increases.
c. XL decreases.
d. load resistance decreases.
15. The transistor dissipation in a class C amplifier decreases when the
a. resonant frequency increases.
b. coil Q increases.
c. load resistance decreases.
d. capacitance increases.
16. The power rating of a transistor can be increased by
a. raising the temperature.
b. using a heat sink.
c. using a derating curve.
d. operating with no input signal.
17. Which class of amplifier produces the least signal
distortion?
a. A.
b. B.
c. C.
d. D.
18. The maximum efficiency of a class AB amplifier is
a. 25%.
b. 50%.
c. 78.5%.
d. Over 90%.
22. In a class A amplifier, the collector current
flows for
a. less than half the cycle.
b. half the cycle.
c. less than the whole cycle.
d. the entire cycle.
23. With class A, the output signal should be
a. unclipped.
b. clipped on positive voltage peak.
c. clipped on negative voltage peak.
d. clipped on negative current peak.
24. Most audio power amplifiers are in IC form.
a. True.
b. False.
25. The power gain of an amplifier is often expressed in
dB. What is the dB power gain of an amplifier with a
power gain of 400?
a. 10 dB.
b. 26 dB.
c. 52 dB.
d. 400 dB.
26. The power gain of an amplifier
a. is the same as the voltage gain.
b. is smaller than the voltage gain.
c. equals output power divided by input power.
d. equals load power.
27. Heat sinks reduce the
a. transistor power.
b. ambient temperature.
c. junction temperature.
d. collector current.
28. When the ambient temperature increases, the maximum transistor power rating
a. decreases.
b. increases.
c. remains the same.
d. none of the above.
19. The quiescent collector current is the same as the
a. dc collector current.
b. ac collector current.
c. total collector current.
d. voltage divider current.
29. If the load power is 300 mW and the dc power is
1.5 W, the efficiency is
a. 0%.
b. 2%.
c. 3%.
d. 20%.
20. The main advantage of a bridged amplifier is
a. greater efficiency.
b. improved frequency response.
c. higher output power with lower supply voltage.
d. no heat sinks are needed.
30. Switching amplifiers are used for
a. audio.
b. RF.
c. both a and b.
d. none of the above.
21. Most modern power amplifiers use
a. MOSFETs.
b. bipolar transistors.
31. Class D amplifiers operated by
a. clipping off all amplitude variations of the input.
b. converting the input signal to a PWM signal.
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c. using a tuned circuit to restore the signal.
d. filtering out the harmonics.
32. Class E and F amplifiers amplify
a. audio.
b. RF.
c. Both a and b.
d. none of the above
33. Most IC power amplifiers must have
a. higher-operating voltages.
b. higher gain.
c. cooling fans.
d. heat sinks.
34. The maximum efficiency of a class B push-pull amplifier is
a. 25%.
b. 50%.
c. 78.5%.
d. 100%.
35. A small quiescent current is necessary with a class
AB push-pull amplifier to avoid
a. crossover distortion.
b. destroying the compensating diodes.
c. excessive current drain.
d. loading the driver stage.
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what happened between the time it was working and the
time that it failed? A common problem is that a new user
came along and tried to use the system, thereby changing
input/output settings.
Next, think up individual tests for each box in the system. If there is no picture on the TV screen, is it completely
dark or is there “snow” or just a blank screen? If the screen
is completely dark, it could mean TV set failure. But if the
screen shows light, chances are the TV inputs have been
changed or lost. Try different input settings to see if you
can get a picture via the cable or satellite receiver. If not,
try a DVD input. Change input settings with the remote as
necessary.
If sound is the problem, try to play a normal CD. Or try
an AM or FM radio station. If the TV won’t play through the
sound system, check input/output settings.
Troubleshooting is often just a trial-and-error process. Just be sure to thoroughly verify the connections
and settings before considering that a box is defective.
More commonly it is not. Most problems seem to be initial interconnections problems or incorrect settings via
the remote controls.
CHAPTER 41 REVIEW QUESTIONS
1. The most common job of an electronics technician is
a. design.
b. circuit analysis.
c. testing.
d. troubleshooting.
2. Which test instrument presents its output in the
frequency domain?
a. Spectrum analyzer.
b. Oscilloscope.
c. Multimeter.
d. Logic analyzer.
3. Which test instrument presents its output in the time
domain?
a. Spectrum analyzer.
b. Oscilloscope.
c. Multimeter.
d. Signal generator.
4. The spectrum analyzer shows what characteristic on
the vertical scale of the output?
a. Voltage.
b. Current.
c. Power.
d. Impedance.
5. A signal generator that produces sine, square, and
triangular waves from about 1 Hz to 6 MHz is
called a(n)
a. RF signal generator.
b. AWG.
c. function generator.
d. frequency synthesizer.
6. Most modern test instruments are
a. analog.
b. digital.
7. What is the first process that an input signal encounters in a modern test instrument?
a. Filtering.
b. Frequency conversion.
c. Digital-to-analog conversion.
d. Analog-to-digital conversion.
8. In a modern test instrument, how is the measurement
actually made?
a. An embedded microcontroller processes the digital
input.
b. Analog circuits interpret the signal and
display it.
c. The signal is directly displayed for the user to
measure.
d. Level comparators decide the signal amplitude.
9. A virtual instrument generally uses what to process
the input signal?
a. Embedded controller.
b. Personal or laptop computer.
c. An FPGA or DSP chip.
d. No processing is done.
10. What makes the measurement in a virtual
instrument?
a. Hardware.
b. Software.
11. What is the name of the software that is used to create
virtual instruments?
a. The C language.
b. Java.
c. LabVIEW.
d. MathCAD.
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12. Which of the following is not part of an AWG?
a. DAC.
b. Frequency synthesizer .
c. Memory.
d. ADC.
13. It is often more economical and faster to replace a
product or subassembly than to repair it.
a. True.
b. False.
14. The fi rst step in most troubleshooting processes
is to
a. isolate the problem.
b. do a visual inspection.
c. verify that the problem exists.
d. check for power.
15. You should not attempt to troubleshoot a piece of
equipment without
a. the documentation.
b. an oscilloscope.
c. multimeter.
d. training.
16. Electronic components are generally more likely to
fail than mechanical components.
a. True.
b. False.
17. A good first step in troubleshooting a circuit is to
a. test all transistors.
b. check for overheated ICs.
c. verify that the correct dc voltages are present.
d. begin signal tracing.
18. In Fig. 41-8, the input to stage 1 is good and the
output from stage 4 is not correct. The problem
lies in
a. stage 1.
b. stage 2.
c. stage 4.
d. any of the stages.
19. In Fig. 41-8, there is no output from stage 1. The
problem is
a. a defective stage 1.
b. no input signal.
c. either a or b.
d. not having enough information to determine.
20. Most detailed troubleshooting should not begin
unless
a. you have the documentation.
b. you are familiar with the equipment.
c. you have been trained on the equipment.
d. all of the above.
21. The most likely component to fail in a system
is a(n)
a. diode.
b. integrated circuit.
c. capacitor.
d. resistor.
22. Which is often the primary goal of troubleshooting a
piece of equipment?
a. Low cost.
b. Minimum downtime.
c. Continued long product life.
d. No need for experienced repairers.
23. For complex digital circuit troubleshooting, the best
instrument is probably the
a. oscilloscope.
b. spectrum analyzer.
c. logic analyzer.
d. signal generator.
24. In systems troubleshooting, it is best to approach the
problem with
a. block diagram analysis.
b. schematic diagram analysis.
c. testing all individual components.
d. replacement of complete subsystems.
25. A quick but expensive and often effective troubleshooting approach is
a. complete unit replacement.
b. component or module substitution.
c. signal tracing to the component level.
d. dc voltage measurement.
CHAPTER 41 PROBLEMS
SECTION 41.3 Circuit Troubleshooting
41.1 In Fig. 41-18, a 15-V signal is applied to the
input of the transistor. The LED does not light.
802
A measurement at the collector of the transistor
reveals a voltage of 15 V. What are the most likely
problems?
Chapter 41
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+5 V
41.4
In Fig. 41-21, the circuits are operating properly
except for a 500-kHz signal riding on the 8-V dc
output. What may be the problem?
LED
R2
120 Vac
60 Hz
R1
Qi
+5 V
Unregulated DC
power supply
+
Figure 41-18
41.2
DC bus
5V
–
Circuit for prob. 41-1.
In Fig. 41-19, the circuit is not performing as it
should. This schematic is all you have. Determine
what the output is supposed to be. Measuring the
output, you get a dc voltage value of –12 V. What is
the problem?
C1
C2
Linear
regulator
DC-DC
converter
+
–
–
8V
Figure 41-21
+
–12 V
Circuit for prob. 41-4.
Power to all of amps: ± 12 Vdc
3 kΩ
1 kΩ
–
–
– 2.5 V
+
+
1 kΩ
A1
A2
2 kΩ
4 kΩ
2 kΩ
+ A
4
–
10 kΩ
Output
–
– 0.6 V
Figure 41-19
+
A3
Circuit for prob. 41-2.
SECTION 41.4 Power Supply Troubleshooting
41.3 Consider the circuit of Fig. 41-20. What is the
desired output? If the output is a series of 60-Hz
pulses across D2, what is the most likely problem?
T1
120 Vac
60 Hz
R1
D1
C1
Voltages in rms
Figure 41-20
Circuit for prob. 41-3.
D2
12 V
SECTION 41.5 Alternative Troubleshooting
Techniques
41.5 One of the PC board modules in a piece of equipment has failed. A replacement board costs $85. The
repair can be made by just plugging in a new board.
On the other hand, a technician can repair the board
in an estimated 2 hours if the $6 defective IC is
available. The technician cost is $45 per hour. What
is the recommended solution?
41.6 If documentation is not available for the device or
system you are troubleshooting, what may be a way
to get that?
SECTION 41.6 System Troubleshooting
41.7 In the garage door example given in Fig. 41-14, the
door will open but not close. What may be the
problem?
41.8 In the home entertainment center of Fig. 41-17,
the TV set is working but you cannot play a
movie DVD. Give several reasons why you
cannot do this.
41.9 The automatic lawn sprinkler system, shown
in Fig. 41-22, has four zones of operation.
Water sprinkler heads in each zone turn on
in sequence for a specific amount of time.
Electronic System Troubleshooting
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Water
source
Sprinkler heads
Valves
Microcontroller
Zone 1
Plastic piping
Programmable
Control
signals
to values
Zone 2
Controls
Zone 3
Zone 4
Plastic piping
AC power
Figure 41-22
An automatic programmable lawn sprinkler system.
A microcomputer-based controller is used to program the system with the zones, days, times, and
durations of the watering. When the system is
operating, the microcontroller provides the signals
804
to turn on the water valves in each section. Zone 3
is not working. Give several possible causes of the
problem.
Chapter 41
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