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WorksheetsEC8452-EC-II::Quiz-5-Power Amps.& DC Converters
Total questions: 30
Worksheet time: 30mins
The output stage of a multistage amplifier is also called ……………
Mixer stage
Power stage
Detector stage
None of the above
………………. coupling is generally employed in power amplifiers
Transformer
RC
direct
Impedance
A class A power amplifier uses …………
Two transistors
Three transistors
One transistor
None of the above
The maximum efficiency of transformer coupled class A power amplifier is ………………
30%
50%
80%
45%
Class……. power amplifier has the highest collector efficiency
C
A
B
AB
Power amplifiers handle …………. signals compare to voltage amplifiers
Small
Very small
Large
None of the above
In class A operation, the operating point is generally located ………. of the d.c. load line.
At cut off point
At the middle
At saturation point
None of the above
A 2-transistor class B power amplifier is commonly called ……….. amplifier
Dual
Push-pull
Symmetrical
Differential
If a transistor is operated in such a way that output current flows for 60o of the input signal, then it is …………… operation
Class A
Class B
Class C
None of the above
If the zero signal dissipation of a transistor is 1W, then power rating of the transistor should be at least ……………….
5 W
33 W
75 W
1 W
When a transistor is cut off……………..
Maximum voltage appears across transistor
Maximum current flows
Maximum voltage appears across load
None of the above
A class A power amplifier is sometimes called ………….. amplifier
Symmetrical
Single-ended
Reciprocating
Differential
The output stage of a multistage amplifier usually employs ………..
Push-pull amplifier
Preamplifier
Class A power amplifier
None of the above
The size of a power transistor is made considerably large to …………
Provide easy handling
Dissipate heat
Facilitate connections
None of the above
Low efficiency of a power amplifier results in ……………….
Low forward bias
Less battery consumption
More battery consumption
None of the above
The push-pull circuit must use …………… operation
Class A
Class C
Class B
Class AB
Power amplifiers generally use transformer coupling because transformer permits……..
Cooling of the circuit
Impedance matching
Distortionless output
Good frequency response
Transformer coupling can be used in …………… amplifiers
Either power or voltage
Only power
Only voltage
None of the above
The disadvantage of impedance matching is that it ………………….
Gives distorted output
Gives low power output
Requires a transformer
None of the above
If the gain versus frequency curve of a transistor amplifier is not flat, then there is................... distortion.
Amplitude
Intermodulation
Frequency
None of the above
Unipolar modulation is generally used in
AC - AC converters
AC - DC converters
DC - AC converters
DC - DC converters
In a flyback converter, the inductor of the buck-boost converter has been replaced by a
Flyback capacitor
Flyback resistor
Flyback transformer
Flyback transistor
Choppers is a
AC - DC converters
AC - AC converters
DC - AC converters
DC - DC converters
The average value of the output voltage in a step - down dc chopper is given by
V 0 = V s
V 0 = D V s
V 0 = V s / D
V 0 = V s / ( 1 - D )
The control method used for PWM dc - dc converter is
Voltage mode control
Current mode control
Hysteric control
All of these
Advantages of Cuk converter is / are
Large number of reactive component
Low stress on switch
Low stress on capacitor
None of these
The output current in PWM DC - DC converters is equal to
Average value of the output inductor current
Product of an average inductor current and a function of duty ratio
Either (1) or (2)
None of these
A step - down choppers can be used in
Electric traction
Electric vehicles
Machine tools
All of these
For a buck converter to reduce the conduction losses in diode
A high on - resistance switch can be added in parallel
A low on - resistance switch can be added in parallel
A high on - resistance switch can be added in series
A low on - resistance switch can be added in series
For bidirectional operation of converters
A parallel combination of controllable switch and a diode is used
A parallel combination of controllable switch and capacitor is used
A series combination of controllable switch and a diode is used
A series combination of controllable switch and a capacitor is used
