Exam
Name___________________________________
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1)
Refer to the figure above. The combination of the two transistors is called
1)
A)
complementary.
B)
NPN.
C)
PNP.
D)
same.
Answer:
Explanation:
A)
B)
C)
D)
2)
A class B amplifier conducts for ________ of the cycle.
2)
A)
180°
B)
90°
C)
360°
D)
45°
Answer:
Explanation:
A)
B)
C)
D)
3)
For a class A CE amplifier, the power dissipation, PDQ
3)
A)
increases when the peak–to–peak load voltage increases.
B)
is zero with no input signal.
C)
is maximum when the transistor is driven to cutoff.
D)
is maximum when there is no input signal.
Answer:
Explanation:
A)
B)
C)
D)
1
4)
Refer to the figure above. The dc voltage across RL was measured at 10 V. A possible problem, if
any, might be that
4)
A)
C3 is shorted.
B)
R1 is open.
C)
C3 is open.
D)
C1 is open.
Answer:
Explanation:
A)
B)
C)
D)
5)
The collector current of a class C amplifier
5)
A)
is an amplified version of the input voltage.
B)
is negatively clamped.
C)
has harmonics.
D)
flows for half a cycle.
Answer:
Explanation:
A)
B)
C)
D)
6)
If a class A amplifier has RC= 4.7 k and RE= 1.5 k and VCC = 24 V, IC(sat) is
6)
A)
3.87 mA.
B)
16 mA.
C)
5.1 mA.
D)
0 mA.
Answer:
Explanation:
A)
B)
C)
D)
7)
Class C amplifiers are almost always
7)
A)
operated at audio frequencies.
B)
tuned RF amplifiers.
C)
transformer–coupled between stages.
D)
wideband.
Answer:
Explanation:
A)
B)
C)
D)
2
8)
For a class AB push–pull amplifier to work properly, the emitter diodes must
8)
A)
match the compensating diodes.
B)
be germanium and the compensating diodes must be silicon.
C)
not match the compensating diodes.
D)
be silicon and the compensating diodes must be germanium.
Answer:
Explanation:
A)
B)
C)
D)
9)
The ac load line usually
9)
A)
equals the dc load line.
B)
is steeper than the dc load line.
C)
has less slope than the dc load line.
D)
is horizontal.
Answer:
Explanation:
A)
B)
C)
D)
10)
Refer to the figure above. This amplifier only shows a positive alternation at the output. The
possible trouble might be that
10)
A)
BE2 is open.
B)
BE1 is open.
C)
C3 is shorted.
D)
R1 is open.
Answer:
Explanation:
A)
B)
C)
D)
11)
If an application for an amplifier requires operation in a linear mode, the most likely choice would
be a
11)
A)
class A.
B)
class B.
C)
class C.
D)
class AB.
Answer:
Explanation:
A)
B)
C)
D)
3
12)
The maximum efficiency for a class A amplifier is about
12)
A)
100%.
B)
50%.
C)
25%.
D)
75%.
Answer:
Explanation:
A)
B)
C)
D)
13)
An application for a power amplifier to operate at radio frequencies is needed. The most likely
choice would be a _________ amplifier.
13)
A)
class A
B)
class B
C)
class C
D)
class AB
Answer:
Explanation:
A)
B)
C)
D)
14)
Refer to the figure above. During the positive input alternation, Q1 is ________ and Q2 is ________.
14)
A)
on, off
B)
off, off
C)
off, on
D)
on, on
Answer:
Explanation:
A)
B)
C)
D)
15)
Heat sinks reduce the
15)
A)
ambient temperature.
B)
junction temperature.
C)
transistor power.
D)
collector current.
Answer:
Explanation:
A)
B)
C)
D)
4
16)
Power MOSFETs have several advantages over bipolar power transistors. Which of the following
statements is not correct?
16)
A)
Have simpler biasing circuits
B)
Can be connected in parallel to increase current capacity
C)
Have a low voltage drop across the device under high voltage and current conditions
D)
Less prone to ESD damage when compared to BJTs
Answer:
Explanation:
A)
B)
C)
D)
17)
Under no–signal or quiescent conditions, the transistors of a class B push–pull amplifier
17)
A)
dissipate very little power.
B)
are in saturation.
C)
have excessively high power dissipation.
D)
get quite hot.
Answer:
Explanation:
A)
B)
C)
D)
18)
If a class A amplifier has a voltage gain of 50 and a current gain of 75, the power gain is
18)
A)
75.
B)
3750.
C)
1500.
D)
50.
Answer:
Explanation:
A)
B)
C)
D)
19)
Push–pull amplifiers often use class ________ amplifiers.
19)
A)
A
B)
B or AB
C)
C
Answer:
Explanation:
A)
B)
C)
20)
The ac load line is the same as the dc load line when the ac collector resistance equals the
20)
A)
ac emitter resistance.
B)
supply voltage divided by collector current.
C)
dc emitter resistance.
D)
dc collector resistance.
Answer:
Explanation:
A)
B)
C)
D)
5
21)
For a Q–point near the center of the dc load line, clipping is more likely to occur on the
21)
A)
negative peak of emitter voltage.
B)
positive peak of output voltage.
C)
positive peak of input voltage.
D)
negative peak of output voltage.
Answer:
Explanation:
A)
B)
C)
D)
22)
In a class AB push–pull amplifier, the transistors are biased slightly above cutoff to avoid
22)
A)
negative feedback.
B)
crossover distortion.
C)
unusually high efficiency.
D)
a low input impedance.
Answer:
Explanation:
A)
B)
C)
D)
23)
To improve the efficiency of an amplifier, you have to
23)
A)
reduce the supply voltage.
B)
increase the dc current.
C)
decrease unwanted power losses.
D)
reduce load power.
Answer:
Explanation:
A)
B)
C)
D)
24)
An amplifier has two load lines because
24)
A)
the dc and ac circuits are different.
B)
it has ac and dc collector resistances.
C)
it has two equivalent circuits.
D)
All of the above.
Answer:
Explanation:
A)
B)
C)
D)
25)
The maximum efficiency of a class B push–pull amplifier is
25)
A)
25 percent.
B)
79 percent.
C)
100 percent.
D)
50 percent.
Answer:
Explanation:
A)
B)
C)
D)
6