ECAD 1.1 Flashcards by Dave Molina

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

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

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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

C. an RF amplifier

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

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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

A. Class A

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

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Which of the following IS NOT amplified
by an amplifier?

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

D. resistance

NOT. Amplifiers work on voltage, current
and power.

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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

A. Class A

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

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A device with gain has the property of:

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

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.

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

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

C. amplifier

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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

B. oscillator

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

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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

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.

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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

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

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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

A. an amplifier

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

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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

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.

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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

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

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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%

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%

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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

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.

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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

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.)

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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

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.

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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%

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%

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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

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

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Class C amplifiers are almost always…

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

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.

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A VCVS amplifier approximates an
ideal…

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

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.

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A device with gain has the property of:

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

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D. amplification

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

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

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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

Which amplifier is commonly used as a
frequency multiplier?

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

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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.

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

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

The least efficient amplifier among all classes is A. class A B. class C C. class AB D. class B

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%

Which of the power amplifiers has the lowest overall efficiency? A. Class D B. Class A C. Class B or AB D. Class C

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%

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

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

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

D. Both common-base and common- collector

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

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%

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

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°

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

D. decrease, increase

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

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)

Which operation gives the maximum distortion? A. Class C B. Class A C. Class AB D. Class B

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

Famous transistor amplifier configuration designed to eliminate the so called Miller effect. A. darlington amplifier B. cascode amplifier C. complementary-symmetry D. differential amplifier

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.

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

A. class B 0/P stage Crossover Distortion occurs in Class B amplifiers because the amplifier is biased at its cut-off point.

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

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

A VCVS amplifier approximates an ideal A. Current amplifier B. Current-to-voltage converter C. Voltage-to-current converter D. Voltage amplifier

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.

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

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.

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

D. is decreased when compared to (see the figure sa ECAD 1.1)

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

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.

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

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

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

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.

Which of the following amplifier is most suited for making tuning circuits? A. Class A B. Class B C. Class C D. Class D

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%.

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

B. voltage series feedback (see the feedback connections at ECAD 1.1)

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

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.

Voltage-series feedback _____ the input impedance of the amplifier. A. has no effect on B. reduces by half C. increases D. decreases

C. increases

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

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.

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°

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%.

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

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.

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

B. Transformers reduce the gain

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°

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°

_____ 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

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)

ECAD 1.1 Flashcards

(53 cards)