1.

The decibel is a unit of

A. Relative signal strength

B. Voltage

C. Power

D. Current

Correct Answer
A. Relative signal strength

Explanation
The decibel is a unit used to measure the relative signal strength. It is commonly used in
telecommunications and audio systems to quantify the difference in power between two
signals. The decibel scale allows for a logarithmic representation of signal strength, making it
easier to compare and analyze different signal levels. Therefore, the correct answer is "relative
signal strength."

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2. An oscillator at RF requires the use of

A. A common drain or common collector circuit

B. A stage with gain

C. A tapped coil

D. A quartz crystal

Correct Answer
B. A stage with gain

Explanation
An oscillator at RF requires the use of a stage with gain because an oscillator is a device that
generates a continuous output signal without any input signal. In order to sustain oscillation,
the circuit needs to provide positive feedback, which is achieved by having a stage with gain.
The gain in the circuit compensates for any losses and ensures that the output signal is
continuously amplified and fed back to the input, resulting in the desired oscillation. The other
options, such as a common drain or common collector circuit, a tapped coil, or a quartz
crystal, are not essential components for generating oscillation in an RF oscillator circuit.

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3. Suppose a circuit is found to have a gain figure of −15 dB. Which of the
following statementsis true?

A. The output signal is stronger than the input signal.

B. The input signal is stronger than the output signal.

C. The input signal is 15 times as strong as the output signal.

D. The output signal is 15 times as strong as the input signal.

Correct Answer
B. The input signal is stronger than the output signal.

Explanation
A gain figure of -15 dB indicates a decrease in signal strength. dB is a logarithmic scale, so a
negative value means a decrease in magnitude. Therefore, the output signal is weaker than
the input signal, making the statement "The input signal is stronger than the output signal"
true.

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4. In an oscillator circuit, the feedback should be

A. As great as possible

B. Kept to a minimum

C. Just enough to sustain oscillation

D. Done through a transformer whose wires can be switched easily

Correct Answer
C. Just enough to sustain oscillation

Explanation
In an oscillator circuit, the feedback should be just enough to sustain oscillation. This means
that the amount of feedback should be carefully controlled so that it provides the necessary
energy to maintain oscillation without causing instability or damping. Too much feedback can
lead to over-amplification and distortion, while too little feedback can result in insufficient
energy to sustain oscillation. Therefore, finding the right balance of feedback is crucial for the
proper functioning of an oscillator circuit.

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5. A power gain of 44 dB is equivalent to which of the following output/input
power ratios?

A. 44:1

B. 160:1

C. 440:1

D. 25,000:1

Correct Answer
D. 25,000:1

Explanation
A power gain of 44 dB means that the output power is 25,000 times greater than the input
power. This can be calculated by using the formula: Power Gain (in dB) = 10 * log10(Output
Power/Input Power). In this case, 44 = 10 * log10(Output Power/Input Power), which can be
rearranged to find that the Output Power/Input Power ratio is 25,000:1.

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6. An RF choke

A. Passes RF signals but blocks dc

B. Passes both RF signals and dc

C. Passes dc but blocks RF signals

D. Blocks both dc and RF signals

Correct Answer
C. Passes dc but blocks RF signals

Explanation
An RF choke is a type of inductor that is designed to block high-frequency signals (RF signals)
while allowing direct current (dc) to pass through. This is achieved by using a coil of wire to
create a magnetic field that opposes the flow of RF signals, effectively blocking them.
However, since direct current does not change in frequency, it is not affected by the magnetic
field and can pass through the choke. Therefore, an RF choke passes dc but blocks RF
signals.

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7. The optimum capacitance values in an amplifier circuit depend on

A. The power-supply voltage

B. The power-supply polarity

C. The input signal strength

D. The input signal frequency

Correct Answer
D. The input signal frequency

Explanation
The optimum capacitance values in an amplifier circuit depend on the input signal frequency.
This is because different frequencies require different amounts of capacitance to achieve
optimal performance. Higher frequencies typically require smaller capacitance values, while
lower frequencies require larger capacitance values. By selecting the appropriate capacitance
values for the input signal frequency, the amplifier circuit can effectively amplify the desired
frequency range and minimize distortion or loss of signal quality.

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8. An oscillator might fail to start for any of the following reasons, except

A. Low battery voltage

B. Low stage gain

C. In-phase feedback

D. A high-impedance load

Correct Answer
C. In-phase feedback

Explanation
In-phase feedback is not a reason for an oscillator to fail to start. In fact, feedback is
necessary for an oscillator to sustain oscillations. It provides the necessary positive feedback
to compensate for energy losses and maintain the desired oscillation frequency. Therefore, in-
phase feedback is not an exception and cannot be a reason for an oscillator to fail to start.

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9. In which of the following FET amplifier types does drain current flow for
exactly 50 percentof the signal cycle?

A. Class A

B. Class AB1

C. Class AB2

D. Class B

Correct Answer
D. Class B

Explanation
In a Class B FET amplifier, the drain current flows for exactly 50 percent of the signal cycle.
This is because in Class B amplifiers, the FET conducts current only when the input signal
exceeds a certain threshold, typically around zero volts. This means that the FET is only active
during half of the input signal cycle, resulting in a drain current flow of 50 percent.

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10. The frequency at which a quartz crystal oscillator produces energy is largely
dependent on

A. The load impedance

B. The physical thickness of the quartz wafer

C. The amount of resistance through the crystal

D. The power-supply voltage

Correct Answer
B. The physical thickness of the quartz wafer

Explanation
The frequency at which a quartz crystal oscillator produces energy is largely dependent on the
physical thickness of the quartz wafer. The thickness of the wafer determines the resonant
frequency of the crystal, as it affects the speed at which the crystal vibrates. A thicker wafer
will vibrate at a lower frequency, while a thinner wafer will vibrate at a higher frequency.
Therefore, the physical thickness of the quartz wafer directly influences the frequency
produced by the oscillator.

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11. Which bipolar amplifier type has some distortion in the signal wave, with
collector currentduring most, but not all, of the cycle?

A. Class A

B. Class AB1

C. Class AB2

D. Class B

Correct Answer
C. Class AB2

Explanation
Class AB2 amplifiers have some distortion in the signal wave because the collector current is
present during most, but not all, of the cycle. In Class AB2 amplifiers, the active device
conducts for more than half of the input cycle, but less than the full cycle. This results in some
distortion in the signal wave. Class AB2 amplifiers are commonly used in audio applications
where moderate distortion is acceptable, such as in power amplifiers for music systems.

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12. An RF oscillator usually

A. Produces an output signal with an irregular wave shape

B. Has most or all of its energy at a single frequency

C. Produces a sound that depends on its waveform

D. Employs an RC circuit to determine the output amplitude

Correct Answer
B. Has most or all of its energy at a single frequency

Explanation
An RF oscillator usually has most or all of its energy at a single frequency. This means that the
oscillator generates a signal that is concentrated at a specific frequency, rather than being
spread out across a range of frequencies. This is important in RF (radio frequency)
applications, where a specific frequency is desired for communication or transmission
purposes. By having most of its energy at a single frequency, the RF oscillator can provide a
stable and reliable signal for these applications.

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13. A class C amplifier can be made linear by

A. Reducing the bias

B. Increasing the drive

C. Using two transistors in push-pull

D. No means; a class C amplifier is always nonlinear

Correct Answer
D. No means; a class C amplifier is always nonlinear

Explanation
A class C amplifier is always nonlinear because it operates with less than 50% of the input
signal cycle. This means that it does not reproduce the entire input waveform accurately,
resulting in distortion. Regardless of any adjustments or modifications, a class C amplifier
cannot be made linear.

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14. A frequency synthesizer has

A. High power output

B. High frequency drift rate

C. Exceptional stability

D. An adjustable wave shape

Correct Answer
C. Exceptional stability

Explanation
A frequency synthesizer is a device used to generate precise and stable frequencies. It is
important for the synthesizer to maintain stability in order to ensure accuracy and reliability in
frequency generation. This stability allows the synthesizer to produce consistent and reliable
output frequencies over time, without significant variations or drift. This is crucial in various
applications such as telecommunications, radar systems, and scientific research, where
precise and stable frequencies are required for proper functioning. Therefore, the exceptional
stability of a frequency synthesizer is a desirable characteristic that sets it apart from other
devices.

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15. A graphic equalizer is a form of

A. Bias control for an NPN bipolar transistor

B. Gain control for an RF oscillator

C. Tone control that can be used in an audio amplifier

D. Circuit for adjusting the waveform of an RF oscillator

Correct Answer
C. Tone control that can be used in an audio amplifier

Explanation
A graphic equalizer is a device that allows users to adjust the tone of audio signals in an
amplifier. It consists of multiple bands, each representing a specific frequency range, which
can be individually adjusted to boost or attenuate the corresponding frequencies. This allows
users to shape the overall sound by emphasizing or reducing certain frequencies. Therefore,
the given answer accurately describes the function of a graphic equalizer as a tone control
that can be used in an audio amplifier.

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16. If the impedance of the load connected to the output of an oscillator is
extremely high,

A. The frequency will drift excessively

B. The power output will be reduced

C. The oscillator might fail to start

D. It is no cause for concern; in fact, it is a good thing.

Correct Answer
D. It is no cause for concern; in fact, it is a good thing.

Explanation
If the impedance of the load connected to the output of an oscillator is extremely high, it is no
cause for concern; in fact, it is a good thing. This is because a high load impedance ensures
that the oscillator is isolated from the load, preventing any unwanted interactions or
disturbances. It allows the oscillator to operate independently and maintain its stability,
without being affected by the load. Therefore, a high load impedance is desirable in this
scenario.

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17. Suppose a certain bipolar-transistor PA is 66 percent efficient. The output
power is 33 W.The dc collector power input is

A. 22 W

B. 50 W

C. 2.2 W

D. Impossible to determine without more information

Correct Answer
B. 50 W

Explanation
Since the bipolar-transistor PA is 66 percent efficient, it means that 66 percent of the input
power is converted into output power. Therefore, to find the dc collector power input, we can
divide the output power by the efficiency percentage. In this case, 33 W divided by 0.66 (66
percent as a decimal) equals 50 W. Hence, the correct answer is 50 W.

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18. A tuned RF PA must always be

A. Set to work over a wide range of frequencies

B. Adjusted for maximum power output

C. Operated at an even harmonic of the input frequency

D. Operated in class C

Correct Answer
B. Adjusted for maximum power output

Explanation
A tuned RF PA must be adjusted for maximum power output because this ensures that the
power amplifier is operating at its highest efficiency and delivering the maximum amount of
power to the load. By adjusting the PA for maximum power output, the system can achieve
optimal performance and transmit signals with the highest possible power level. This is
important in applications where high power transmission is required, such as in wireless
communication systems or broadcasting.

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 19. Class B amplification can be used to obtain low distortion for audio
applications

A. By connecting two amplifiers in cascade, thereby maximizing the gain and

generating a pure sine wave output.

B. By biasing the bipolar transistor or FET beyond cutoff or pinchoff, thereby

ensuring that the output is in phase with the input.

C. By connecting two identical bipolar transistors or FETs, biased exactly at

cutoff or pinchoff, in a push-pull configuration.

D. By biasing the bipolar transistor or FET in the middle of the straight-line

portion of the characteristic curve.

Correct Answer
C. By connecting two identical bipolar transistors or FETs, biased exactly at cutoff or pinchoff,
in a push-pull configuration.

Explanation
Class B amplification is a technique used to minimize distortion in audio applications. By
connecting two identical bipolar transistors or FETs in a push-pull configuration, both
transistors are biased exactly at cutoff or pinchoff, ensuring that each transistor operates in
its active region for half of the input waveform. This configuration allows for efficient power
utilization and eliminates the need for a biasing voltage, resulting in a pure sine wave output
with low distortion.

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