ECAD 1.1

Question 1

For class B operation, the collector
current flows

A. The whole cycle
B. Less than a quarter of a cycle
C. Less than half a cycle
D. Half the cycle

Answer 1

D. Half the cycle

For power amplifiers:
Class A = conducts for the whole cycle
Class B = conducts for half of the cycle
Class AB = conducts for more than half of the cycle but less than a full cycle
Class C = conducts for less than half of a cycle

Question 2

To increase the level of very weak radio
signals from an antenna, you would use.

A. an RF oscillator
B. an audio amplifier
C. an RF amplifier
D. an audio oscillator

Answer 2

C. an RF amplifier

INCREASE WEAK RADIO signals.A
Radio-Frequency (RF) amplifier must be
used.

Question 3

Which of the following amplifier class
have highest linearity and lowest
distortion?

A. Class A
B. Class B push-pull
C. Class B
D. Class C

Answer 3

A. Class A

Class A amplifier have highest linearity and lowest distortion, followed by Class AB, then Class B, and finally Class C.

Question 4

Which of the following IS NOT amplified
by an amplifier?

A. power
B. voltage
C. current
D. resistance

Answer 4

D. resistance

NOT. Amplifiers work on voltage, current
and power.

Question 5

Which of the following amplifier class
have highest linearity and lowest
distortion?

A. Class A
B. Class B
C. Class C
D. Class B push-pull

Answer 5

A. Class A

Class A amplifier have highest linearity and lowest distortion, followed by Class AB, then Class B, and finally Class C.

Question 6

A device with gain has the property of:

A. oscillation
B. modulation
C. attenuation
D. amplification

Answer 6

D. amplification

Gain and Amplification are synonymous.’Attenuation’ is a loss (opposite to gain).’Oscillation’ is the production of an
Alternating Current (AC) signal.
‘Modulation’ is the impression of a
message onto another signal.

Question 7

A device labelled “Gain = 10 dB” is likely
to be an:

A. oscillator
B. attenuator
C. amplifier
D. audio fader

Answer 7

C. amplifier

Gain and Amplification are synonymous.’Attenuation’ is a loss (opposite to gain).’Oscillation’ is the production of an
Alternating Current (AC) signal.
‘Modulation’ is the impression of a
message onto another signal.

Question 8

Positive feedback is used to produce a
special type of circuit called a(n)

A. inverting amplifier
B. oscillator
C. all of these choices
D. noninverting amplifier

Answer 8

B. oscillator

Amplifier circuits uses negative
feedback to improve its bandwidth,
while an oscillator needs positive
feedback due to its positive effect in
gain.

Question 9

With an ICVS amplifier, the circuit
approximates an ideal

A. Voltage amplifier
B. Voltage-to-current converter
C. Current amplifier
D. Current-to-voltage converter

Answer 9

D. Current-to-voltage converter

ICVS means current-controlled voltage source. It is a type of amplifier where in the controlling input is current and the controlled parameter at the output is voltage, hence it can be considered as a current-to-voltage converter.

Question 10

Which type of power amplifier is biased
for operation at less than 180° of the
cycle?

A. Class AB
B. Class B
C. Class C
D. Class A

Answer 10

C. Class C

Class A = full 360° operation
Class B = 180° operation
Class AB = between 180° and 306° operation
Class C = less than 180° operation

Question 11

A circuit designed to increase the level
of its input signal is called:

A. an amplifier
B. an oscillator
C. a modulator
D. a receiver

Answer 11

A. an amplifier

INCREASE. An amplifier reproduces its input signal into a larger output signal (more voltage, more current, more power).

Question 12

Bandwidth of amplifier is

A. Difference between upper cut-off
frequency and lower cut-off frequency
B. Average of upper cut-off frequency and
lower cut-off frequency
C. Sum of upper cut-off frequency and lower
cut-off frequency
D. lindependent to cut off frequency

Answer 12

A. Difference between upper cut-off
frequency and lower cut-off frequency

3dB bandwidth of an amplifier is the
difference between upper cut-off
frequency and lower cut-off frequency.
The unity gain bandwidth is the
difference between frequencies were
gain is 1.

Question 13

Which type of power amplifier is biased
for operation at less than 180° of the cycle?

A. Class AB
B. Class B
C. Class C
D. Class A

Answer 13

C. Class C

Class A = full 360° operation
Class B = 180° operation
Class AB = between 180° and 306° operation
Class C = less than 180° operation

Question 14

What is the maximum efficiency of a
class A circuit with a direct or series-fed
load connection?

A. 78.5%
B. 90%
C. 25%
D. 50%

Answer 14

C. 25%

For max. efficiency:
Class A = 25% (if direct coupled), 50% (if
transformer-coupled)
Class B = 78.5%
Class C= between class A and class B
Class C = above 90%

Question 15

The input impedance of a shunt
feedback amplifier _____ the input
impedance of the original amplifier.

A. has no effect on
B. is decreased when compared to
C. is increased when compared to
D. is reduced by half when compared to

Answer 15

B. is decreased when compared to

In the input side, the connection is in
parallel/shunt, meaning, the input
impedance decreases in this type of
feedback connection.

Question 16

Which class of amplifier operates in the linear region for only a small part of the input cycle?

A. AB
B. B
C. A
D. C

Answer 16

D. C

Class C amplifiers conduction angle is less than 180°, meaning it operates for only a small part of the input cycle (less than half of the full input cycle.)

Question 17

Bandwidth of amplifier is

A. Sum of upper cut-off frequency and lower
cut-off frequency
B. Independent to cut off frequency
C. Average of upper cut-off frequency and
lower cut-off frequency
D. Difference between upper cut-off
frequency and lower cut-off frequency

Answer 17

D. Difference between upper cut-off
frequency and lower cut-off frequency

3dB bandwidth of an amplifier is the
difference between upper cut-off
frequency and lower cut-off frequency.
The unity gain bandwidth is the
difference between frequencies were
gain is 1.

Question 18

What is the maximum efficiency of a
class A circuit with a direct or series-fed
load connection?

A. 78.5%
B. 90%
C. 25%
D. 50%

Answer 18

C. 25%

For max. efficiency:
Class A = 25% (if direct coupled), 50% (if
transformer-coupled)
Class B = 78.5%
Class C = between class A and class B
Class C = above 90%

Question 19

For a transistor to function as an
amplifier,

A. Both the EB and CB junctions must be
reverse-biased
B. Both the EB and CB junctions must be
forward-biased
C. The CB junction must be forward-biased
and the EB junction must be reverse-biased
D. The EB junction must be forward-biased and the CB junction must be reverse-biased

Answer 19

D. The EB junction must be forward-biased and the CB junction must be reverse-biased

Question 20

Class C amplifiers are almost always…

A. Tuned RF amplifiers
B. Operated at audio frequencies
C. Wideband
D. Transformer-coupled between stages

Answer 20

A. Tuned RF amplifiers

The output of a class C amplifier needs to be connected to a resonant circuit or tuned circuit in order to have a sinusoidal waveform at the output similar to what it is in its input.

Question 21

A VCVS amplifier approximates an
ideal…

A. Voltage amplifier
B. Current-to-voltage converter
C. Current amplifier
D. Voltage-to-current converter

Answer 21

A. Voltage amplifier

VCVS means voltage controlled voltage source. It is a type of amplifier where in the controlling input is voltage and the controlled parameter at the output is also voltage, hence it is a voltage
amplifier.

Question 22

A device with gain has the property of:

A. modulation
B. attenuation
C. oscillation
D. amplification

Answer 22

D. amplification

Gain and Amplification are synonymous.’Attenuation’ is a loss (opposite to gain).’Oscillation’ is the production of an
Alternating Current (AC) signal.
‘Modulation’ is the impression of a
message onto another signal.

Question 23

The Q-point is at cutoff for class ____ operation.

A. C
B. A
C. B
D. AB

Answer 23

C. B

Q point location:
Class A = at the linear region/active region
Class B = exactly at cut-off
Class AB = a little above cut-off
Class C = below cut-off

Question 24

Which amplifier is commonly used as a
frequency multiplier?

A. class B
B. all of these choices
C. class A
D. class C

Answer 24

D. class C

Class C has the most distorted output among the class of amplifiers (A, AB,and B). The more distorted the output waveform the greater is the harmoniccontents of the signal.
Since, harmonics are signals which are integer multiple of the fundamental signal, class C
amplifier is the best option to use for a
frequency multiplier circuits.

Question 25

In a class A amplifier, the collector
current flows for

A. The entire cycle
B. Half the cycle
C. Less than half the cycle
D. Less than the whole cycle

Answer 25

A. The entire cycle

For power amplifiers:
Class A = conducts for the whole cycle
Class B = conducts for half of the cycle
Class AB = conducts for more than half of the cycle but less than a full cycle
Class C = conducts for less than half of a cycle

Question 26

The least efficient amplifier among all
classes is

A. class A
B. class C
C. class AB
D. class B

Answer 26

A. class A

For max. efficiency:
Class A = 25% (if direct coupled),50% (if
transformer-coupled)
Class B = 78.5%
Class C = between class A and class B
Class C= above 90%
Class D= almost 100%

Question 27

Which of the power amplifiers has the
lowest overall efficiency?

A. Class D
B. Class A
C. Class B or AB
D. Class C

Answer 27

B. Class A

For max. efficiency.
Class A = 25% (if direct coupled), 50% (if
transformer-coupled)
Class B = 78.5%
Class C = between class A and class B
Class C= above 90%
Class D = almost 100%

Question 28

A class _____ amplifier is biased
slightly above cutoff and operates in the linear region for slightly more than 180° of the input cycle.

A. C
B. B
C. AB
D. A

Answer 28

C. AB

Q point location:
Class A = at the linear region/active region
Class B = exactly at cut-off
Class AB = a little above cut-off
Class C = below cut-off

Question 29

Which transistor configuration offers no
phase reversal at the output?

A. Common-base
B. Common-emitter
C. Common-collector
D. Both common-base and common-
collector

Answer 29

D. Both common-base and common-
collector

Question 30

Categorize the power efficiency of each
class of amplifier, from worst to best.

A. A, AB, B, D
B. A, B, D, AB
C. A, AB, D, B
D. A, B, AB,D

Answer 30

A. A, AB, B, D

For max. efficiency:
Class A = 25% (if direct coupled), 50% (if
transformer-coupled)
Class B = 78.5%
Class C = between class A and class B
Class C= above 90%
Class D = almost 100%

Question 31

If a transistor amplifier provides a 360°
output signal, it is classified as

A. class B
B. class C
C. class AB
D. class A

Answer 31

D. class A

Angle of Conduction Comparison of
Power Amplifiers:
Class A → 360°
Class B → 180°
Class AB → between 180° and 360°
Class C → less than 180°

Question 32

Voltage feedback connections tend to _____ the output impedance. Current
feedback connections tend to _____ the
output impedance.

A. increase, decrease
B. decrease, decrease
C. increase, increase
D. decrease, increase

Answer 32

D. decrease, increase

Question 33

Cascaded amplifiers total decibel gain
is equal to

A. The sum of the individual gains
B. The quotient of the individual gains
C. The product of the individual gains
D. The difference of the individual gains

Answer 33

A. The sum of the individual gains

CASCADED AMPLIFIERS
- a cascade connection is a series connection with the output of one stage then applied as input to the second stage
- this connection provides a multiplication of the
gain of each stage for a larger overall gain

(see more at ECAD 1.1 album)

Question 34

Which operation gives the maximum
distortion?

A. Class C
B. Class A
C. Class AB
D. Class B

Answer 34

A. Class C

Distortion Comparison of Power
Amplifiers:
Class A → low
Class B → high
Class AB → moderate
Class C → very high

Question 35

Famous transistor amplifier
configuration designed to eliminate the
so called Miller effect.

A. darlington amplifier
B. cascode amplifier
C. complementary-symmetry
D. differential amplifier

Answer 35

B. cascode amplifier

The cascode amplifier is combined common-emitter and common-base configuration or a common-source followed by a common-gate.
This amplifier configuration is popular at
high-frequency applications due to the
reason that it can eliminate the so
called Miller effect.

In electronics, the Miller effect accounts
for the increase in the equivalent input
capacitance of an amplifier due to
amplification of the effect of capacitance between the input and output terminals.
This can reduce the bandwidth of the amplifier, restricting its range of operation to lower frequencies.

Question 36

Crossover distortion behaviour is
characteristic of

A. class B 0/P stage
B. common pulse 0/P state
C. class A 0/P stage
D. class AB output stage

Answer 36

A. class B 0/P stage

Crossover Distortion occurs in Class B
amplifiers because the amplifier is
biased at its cut-off point.

Question 37

The transistors of a class B push-pull
emitter follower are biased at or near

A. The center of the dc load line
B. The center of the ac load line
C. Cutoff
D. Saturation

Answer 37

C. Cutoff

Q point locations for amplifiers are as
follows:
Class A = active/linear region
Class B = at cut-off
Class C = below cut-off
Class AB = a little above cut-off

Question 38

A VCVS amplifier approximates an ideal

A. Current amplifier
B. Current-to-voltage converter
C. Voltage-to-current converter
D. Voltage amplifier

Answer 38

D. Voltage amplifier

(look at the figure on ECAD 1.1 album, love)

Since the controlling input and the
controlled output is both voltage
VCVS is sometimes called Voltageto-Voltage Converter and/or simply Voltage Amplifier.

Question 39

The collector current of a class C amplifier

A. Flows for half a cycle
B. Is an amplified version of the input voltage
C. Has harmonics
D. Is negatively clamped

Answer 39

C. Has harmonics

Class C amplifier produces an output
not an exact replica of the input
waveform. This means that the signal
has distortion, and since distorted
signal contains harmonic components,
we can say that the output (collector
current) of a class C amplifier contain
harmonics.

Question 40

The input impedance of a voltage-shunt
feedback amplifier _____ the input
impedance of its op-amp.

A. is increased when compared to
B. is reduced by half when compared to
C. has no effect on
D. is decreased when compared to

Answer 40

D. is decreased when compared to

(see the figure sa ECAD 1.1)

Question 41

The transresistance of an amplifier is
the ratio of its…

A. Output voltage to input current
B. Output voltage to input voltage
C. Output current to input voltage
D. Input voltage to output current

Answer 41

A. Output voltage to input current

“TRANS” - indicates that it is output
quantity over an input quantity
“RESISTANCE” - indicates that it is a
ratio of voltage to current
Therefore, transresistance indicates a
ratio of output voltage to input current.

Question 42

Negative feedback reduces…

A. Loop gain
B. Input offset voltage
C. Distortion
D. Feedback fraction

Answer 42

C. Distortion

The following are major effects of
having a negative feedback in a circuit:

decreases gain
increases bandwidth
increasing stability
reducing noise and distortion

Question 43

With negative feedback, the returning
signal…

A. Is proportional to differential voltage gain
B. Aids the input signal
C. Is proportional to output current
D. Opposes the input signal

Answer 43

D. Opposes the input signal

Negative feedback is when the input signal is 180° out of phase with the input signal in the mixing/summing circuit.
Since the feedback (or returning signal) is 180° out of phase it will oppose the input signal.

Question 44

Which of the following amplifier is most
suited for making tuning circuits?

A. Class A
B. Class B
C. Class C
D. Class D

Answer 44

C. Class C

Class C power amplifier is a type of
amplifier where the active element
(transistor) conduct for less than one
half cycle of the input signal. Less than
one half cycle means the conduction
angle is less than 180° and its typical
value is 80° to 120°. The reduced
conduction angle improves the
efficiency to a great extend but causes a
lot of distortion. Theoretical maximum
efficiency of a Class C amplifier is
around 90%.

Question 45

The feedback circuit connection shown
here is _____

(see the figure at ECAD 1.1)

A. current series feedback
B. voltage series feedback
C. current shunt feedback
D. voltage shunt feedback

Answer 45

B. voltage series feedback

(see the feedback connections at ECAD 1.1)

Question 46

With an ICVS amplifier, the circuit
approximates an ideal

A. Voltage-to-current converter
B. Current-to-voltage converter
C. Current amplifier
D. Voltage amplifier

Answer 46

B. Current-to-voltage converter

ICVS means current-controlled voltage source. It is a type of amplifier where in the controlling input is current and the controlled parameter at the output is voltage, hence it can be considered as a current-to-voltage converter.

Question 47

Voltage-series feedback _____ the
input impedance of the amplifier.

A. has no effect on
B. reduces by half
C. increases
D. decreases

Answer 47

C. increases

Question 48

What is a cascode amplifier?

A. A cascade of two CB amplifiers
B. A cascade of CB and CC amplifiers
C. A cascade of two CE amplifiers
D. A cascade of CE and CB amplifiers

Answer 48

D. A cascade of CE and CB amplifiers

A cascode amplifier is a cascade
network of CE and CB amplifiers, or CS
and CG amplifiers.

Question 49

Which of these is not true for a class B
amplifier?

A. They have an efficiency less than that
of class A amplifiers
B. It has zero DC bias
C. The quiescent power dissipation is zero
D. The conduction angle is only 180°

Answer 49

A. They have an efficiency less than that
of class A amplifiers

Class A amplifier has a maximum
efficiency of only 25% for direct-coupled and 50% for transformer-coupled while for class B, the maximum efficiency is 78.5%.

Question 50

A gain of -15 dB in a circuit means that:

A. The output signal is 15 times as strong as
the input
B. The output signal is stronger than the input
C. The input signal is 15 times as strong as
theoutput
D. The input signal is stronger than the
output

Answer 50

D. The input signal is stronger than the
output

Negative dB value for the ratio of output
to input of a circuit means that the
output value is lower than the input
value.

Question 51

A disadvantage of transfer coupling, as
opposed to capacitive coupling, is that:

A. Transformers can’t match impedances
B. Transformers reduce the gain
C. Transformers can’t work above audio
frequencies
D. Transformers cost more

Answer 51

B. Transformers reduce the gain

Question 52

By how much does the output signal
vary for a class AB power amplifier?

A. 180°
B. Less than 180°
C. 360°
D. Between 180° and 360°

Answer 52

D. Between 180° and 360°

Angle of Conduction Comparison of
Power Amplifiers:
Class A → 360°
Class B → 180°
Class AB → between 180° and 360°
Class C → less than 180°

Question 53

_____ in a current-controlled voltage
source circuit.

A. The output current depends on the output
voltage source
B. The input current depends on the input
voltage source
C. The input current depends on the output
voltage
D. The output voltage depends on the
input current

Answer 53

D. The output voltage depends on the
input current

The following are the type of amplifier
based on controlling input and
controlled output parameters:

(kindly look for the figure at ECAD 1.1)