E7B: Amplifiers: Class of operation; vacuum tube and solid-state circuits; distortion and intermodulation; spurious and parasitic suppression; microwave amplifiers
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
Which class of amplifier, of the types shown, provides the highest efficiency?
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
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
Which of the following amplifier types reduces or eliminates even-order harmonics?
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
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
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
In Figure E7-1, what is the purpose of R1 and R2?
In Figure E7-1, what is the purpose of R3?
Output load resistor
What type of circuit is shown in Figure E7-1?
Common emitter amplifier
Switching voltage regulator
Linear voltage regulator
Emitter follower amplifier
In Figure E7-2, what is the purpose of R?
In Figure E7-2, what is the purpose of C2?
What is one way to prevent thermal runaway in a transistor amplifier?
Use degenerative emitter feedback
Select transistors with high beta
All of the above
What is the effect of intermodulation products in a linear power amplifier?
Transmission of spurious signals
Creation of parasitic oscillations
All of the above
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
Which of the following is a characteristic of a grounded-grid amplifier?
Low input impedance
High power gain
High filament voltage
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
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
Which of the following devices is generally best suited for UHF or microwave power amplifier applications?
Silicon Controlled Rectifier
● = Unseen
● = Weak
● = Review
● = Learned
● = Incorrect answer