E7B: Amplifiers: Class of operation; vacuum tube and solid-state circuits; distortion and intermodulation; spurious and parasitic suppression; microwave amplifiers
E7B01:
For what portion of a signal cycle does a Class AB amplifier operate?
More than 180 degrees but less than 360 degrees
Exactly 180 degrees
The entire cycle
Less than 180 degrees
E7B02:
Which class of amplifier, of the types shown, provides the highest efficiency?
Class C
Class A
Class B
Class AB
E7B03:
Where on the load line of a Class A common emitter amplifier would bias normally be set?
Approximately half-way between saturation and cutoff
Where the load line intersects the voltage axis
At a point where the bias resistor equals the load resistor
At a point where the load line intersects the zero bias current curve
E7B04:
What can be done to prevent unwanted oscillations in a power amplifier?
Install parasitic suppressors and/or neutralize the stage
Tune the stage for maximum SWR
Tune both the input and output for maximum power
Use a phase inverter in the output filter
E7B05:
Which of the following amplifier types reduces or eliminates even-order harmonics?
Push-pull
Push-push
Class C
Class AB
E7B06:
Which of the following is a likely result when a Class C rather than a class AB amplifier is used to amplify a single-sideband phone signal?
The signal may become distorted and occupy excessive bandwidth
Intermodulation products will be greatly reduced
Overall intelligibility will increase
Part of the transmitted signal will be inverted
E7B07:
How can a vacuum-tube power amplifier be neutralized?
By feeding back an out-of-phase component of the output to the input
By increasing the grid drive
By reducing the grid drive
By feeding back an in-phase component of the output to the input
E7B08:
Which of the following describes how the loading and tuning capacitors are to be adjusted when tuning a vacuum tube RF power amplifier that employs a pi-network output circuit?
The tuning capacitor is adjusted for minimum plate current, while the loading capacitor is adjusted for maximum permissible plate current
The loading capacitor is set to maximum capacitance and the tuning capacitor is adjusted for minimum allowable plate current
The tuning capacitor is set to maximum capacitance and the loading capacitor is adjusted for minimum plate permissible current
The loading capacitor is adjusted to minimum plate current while alternately adjusting the tuning capacitor for maximum allowable plate current
E7B09:
In Figure E7-1, what is the purpose of R1 and R2?
Fixed bias
Load resistors
Self bias
Feedback
E7B10:
In Figure E7-1, what is the purpose of R3?
Self bias
Fixed bias
Emitter bypass
Output load resistor
E7B11:
What type of circuit is shown in Figure E7-1?
Common emitter amplifier
Switching voltage regulator
Linear voltage regulator
Emitter follower amplifier
E7B12:
In Figure E7-2, what is the purpose of R?
Emitter load
Fixed bias
Collector load
Voltage regulation
E7B13:
In Figure E7-2, what is the purpose of C2?
Output coupling
Emitter bypass
Input coupling
Hum filtering
E7B14:
What is one way to prevent thermal runaway in a transistor amplifier?
Use degenerative emitter feedback
Neutralization
Select transistors with high beta
All of the above
E7B15:
What is the effect of intermodulation products in a linear power amplifier?
Transmission of spurious signals
Creation of parasitic oscillations
Low efficiency
All of the above
E7B16:
Why are third-order intermodulation distortion products of particular concern in linear power amplifiers?
Because they are relatively close in frequency to the desired signal
Because they are relatively far in frequency from the desired signal
Because they invert the sidebands causing distortion
Because they maintain the sidebands, thus causing multiple duplicate signals
E7B17:
Which of the following is a characteristic of a grounded-grid amplifier?
Low input impedance
High power gain
High filament voltage
Low bandwidth
E7B18:
What is a klystron?
A VHF, UHF, or microwave vacuum tube that uses velocity modulation
A high speed multivibrator
An electron-coupled oscillator utilizing a pentode vacuum tube
An oscillator utilizing ceramic elements to achieve stability
E7B19:
What is a parametric amplifier?
A low-noise VHF or UHF amplifier relying on varying reactance for amplification
A type of bipolar operational amplifier with excellent linearity derived from use of very high voltage on the collector
A high power amplifier for HF application utilizing the Miller effect to increase gain
An audio push-pull amplifier using silicon carbide transistors for extremely low noise
E7B20:
Which of the following devices is generally best suited for UHF or microwave power amplifier applications?
FET
Nuvistor
Silicon Controlled Rectifier
Triac
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