EAC 4: Feedback and Oscillators

Q1. Which of the following is a characteristic of a cascaded amplifier?
a. Double each amplifier's gain
b. Each amplifier's gain is increased
c. Increased overall gain
d. Total gain is decreased

c. Increased overall gain

Q2. What happens to the input resistance of an amplifier employing voltage-series feedback?
a. It is increased
b. It remains the same
c. It is decreased
d. Equals infinity

a. It is increased

Q3. What happens to the output resistance of an amplifier employing voltage-shunt feedback?
a. It is increased
b. It remains the same
c. It is decreased
d. Equals infinity

c. It is decreased

Q4. If the gain of an amplifier without feedback is 10 and with negative feedback is 8, then the feedback fraction is
a. 0.025
b. 0.9
c. 0.8
d. 0.225

a. 0.025

Q5. Type of feedback employed in oscillations
a. Negative
b. Zero
c. Positive
d. Capacitive

c. Positive

Q6. The condition that product of the feedback fraction and the open-loop gain should be 1 for oscillation is known as
a. Positive feedback
b. Barkhausen criterion
c. Negative feedback
d. Oscillation requirement

b. Barkhausen criterion

Q7. _____ is the characteristic of an oscillator that enables it to sustain oscillation after removal of the control stimulus
a. Momentum
b. Fly-wheel effect
c. Damping
d. Forced oscillations

b. Fly-wheel effect

Q8. _____ is the progressive decay with time in the amplitude of the free oscillation in a circuit.
a. Decrement
b. Pulse decay time
c. Damping
d. Dancing

c. Damping

Q9. An LC oscillation that employs a tapped capacitor in parallel with an inductor
a. Armstrong oscillator
b. Hartley oscillator
c. Clapp oscillator
d. Colpitts oscillator

d. Colpitts oscillator

Q10. The energy of an oscillator can be sourced by
a. Coupling a small coil close to the tube
b. Capacitive or inductive coupling from tuned circuit
c. Inserting a resistor in the grid circuit
d. Connecting capacitors across the supply

b. Capacitive or inductive coupling from tuned circuit

Q11. An LC oscillator that employs a tapped inductor in parallel with a capacitor.
a. Armstrong
b. Hartley
c. Clapp
d. Colpitts

b. Hartley

Q12. A variation of Colpitts oscillator which employs a small capacitance in addition to the two capacitors to reduce the effect of stray capacitance.
a. Armstrong oscillator
b. Hartley oscillator
c. Clapp
d. Wien Bridge oscillator

c. Clapp

Q13. Oscillator that employs a transformer in parallel with a capacitor
a. Armstrong oscillator
b. Hartley oscillator
c. Clapp
d. Colpitts oscillator

a. Armstrong oscillator

Q14. An oscillator in which a piezoelectric crystal is connected in a tank circuit between the input and output.
a. Clapp
b. Armstrong
c. Colpitts
d. Pierce

d. Pierce

Q15. It is a measure of the ability of an oscillator to maintain a constant frequency and amplitude.
a. Stability
b. Figure of merit
c. Quality factor
d. Sensitivity

a. Stability

Q16. It is the ability of some material to convert electrical energy to mechanical energy and vice versa.
a. Magnetostriction
b. Piezoelectricity
c. Coercivity
d. Conductivity

b. Piezoelectricity

Q17. What determines the resonant frequency of a crystal?
a. External components
b. The temperature of the crystal
c. The size and thickness of the crystal material
d. The hermetic seal

c. The size and thickness of the crystal material

Q18. Which of the following exhibits the best piezoelectric activity?
a. Carbon
b. Quartz
c. Rochelle salt
d. Tourmaline

c. Rochelle salt

Q19. Which of the following is the toughest?
a. Carbon
b. Quartz
c. Rochelle salt
d. Tourmaline

d. Tourmaline

Q20. Which of the following is the least expensive?
a. Diamond
b. Quartz
c. Rochelle salt
d. Tourmaline

b. Quartz

Q21. A Quartz crystal is made up of what kind of material?
a. Carbon
b. SiO₂
c. Ceramic
d. Lead

b. SiO₂

Q22. An oscillator that employs 3 RC sections to produce a 180° feedback phase shift
a. RC phase shift oscillator
b. Hartley oscillator
c. Wien bridge oscillator
d. Colpitts oscillator

a. RC phase shift oscillator

Q23. It is a low-distortion, tunable, high-purity sine-wave generator for frequencies of 5 Hz to 500 kHz.
a. RC phase shift oscillator
b. Hartley oscillator
c. Wien bridge oscillator
d. Colpitts oscillator

c. Wien bridge oscillator

Q24. What is the oscillator of a radar receiver?
a. Detector
b. Product detector
c. Hartley oscillator
d. Klystron oscillator

d. Klystron oscillator

Q25. Circuits that generate non-sinusoidal waveforms that are designed to have one, two or no stable output states.
a. Converter
b. Clipper
c. Rectifier
d. Multivibrator

d. Multivibrator

Q26. A type of Multivibrator that has no stable state
a. Monostable
b. Bistable
c. Astable
d. Zerostable

c. Astable

Q27. An oscillator that uses the charge/discharge characteristic of a capacitor or inductor to produce an oscillating output
a. Relaxation oscillator
b. Phase shift oscillator
c. Bistable oscillator
d. Crystal oscillator

a. Relaxation oscillator

Q28. A filter that uses amplifiers such as transistor and op-amp as one of its components
a. Active
b. LPF
c. Passive
d. BPF

a. Active

Q29. Frequency wherein the power gain is one half of the maximum possible power gain for a given amplifier
a. Beamwidth
b. Center frequency
c. Bandwidth
d. Cutoff frequency

d. Cutoff frequency

Q30. Change in frequency by a factor of 2?
a. Decade
b. Fascade
c. Octave
d. Octane

c. Octave

Q31. Change in frequency by a factor of 10?
a. Decade
b. Fascade
c. Octave
d. Octane

a. Decade

Q32. Rate of transition from pass band to stop band or vice versa.
a. Decay rate
b. Band rate
c. Transition rate
d. Roll-off rate

d. Roll-off rate

Q33. It’s the range of frequency a circuit allows to pass through
a. Pass band
b. Band pass
c. Stop band
d. Band stop

a. Pass band

Q34. The _____ the Q of a circuit, the narrower is its bandwidth.
a. Higher
b. Lower
c. Selective
d. Broader

a. Higher

Q35. Another name for band reject filter
a. Notch
b. Tuned circuit
c. Stop band
d. BPF

a. Notch

Q36. Find the half-power bandwidth of a resonant circuit which has a resonant frequency of 1.8 MHz and a Q of 95
a. 18.9 kHz
b. 189 Hz
c. 58.7 kHz
d. 1.89 kHz

a. 18.9 kHz

Q37. Filter that is characterized by a relatively flat passband and slow roll-off rate
a. Butterworth
b. Elliptic
c. Chebyshev
d. Notch

a. Butterworth

Q38. Filter that is characterized by ripple at the passband and fast roll-off rate
a. Butterworth
b. Elliptic
c. Chebyshev
d. Notch

c. Chebyshev

Q39. An LC circuit resonates at 2000 kHz and has a Q of 100. Find the lower and upper cut-off frequencies.
a. 1980 kHz, 2020 kHz
b. 1950 kHz, 2050 kHz
c. 1990 kHz, 2010 kHz
d. 1900 kHz, 2100 kHz

c. 1990 kHz, 2010 kHz

Q40. What is the resonant frequency of a circuit when L is 1 µH and C is 10 pF in series?
a. 50.3 MHz
b. 15.9 MHz
c. 15.9 kHz
d. 50.3 kHz

a. 50.3 MHz