1 . An oscillator always needs an amplifier with
a. Positive feedback
b. Negative feedback
c. Both types of feedback
d. An LC tank circuit
a
2. The voltage that starts an oscillator is caused by
a. Ripple from the power supply
b. Noise voltage in resistors
c. The input signal from a generator
d. Positive feedback
b
3. The Wien-bridge oscillator is useful
a. At low frequencies
b. At high frequencies
c. With LC tank circuits
d. At small input signals
a
4. A lag circuit has a phase angle that is
a. Between 0 and +90 degrees
b. Greater than 90 degrees
c. Between 0 and -90 degrees
d. The same as the input voltage
c
5. A coupling circuit is a
a. Lag circuit
b. Lead circuit
c. Lead-lag circuit
d. Resonant circuit
b
6. A lead circuit has a phase angle that is
a. Between 0 and +90 degrees
b. Greater than 90 degrees
c. Between 0 and -90 degrees
d. The same as the input voltage
a
7. A Wien-bridge oscillator uses
a. Positive feedback
b. Negative feedback
c. Both types of feedback
d. An LC tank circuit
c
8. Initially, the loop gain of a Wien-bridge oscillator is
a. 0
b. 1
c. Low
d. High
d
9. A Wien bridge is sometimes called a
a. Notch filter
b. Twin-T oscillator
c. Phase shifter
d. Wheatstone bridge
a
10. To vary the frequency of a Wien bridge, you can vary
a. One resistor
b. Two resistors
c. Three resistors
d. One capacitor
b
11. The phase-shift oscillator usually has
a. Two lead or lag circuits
b. Three lead or fag circuits
c. A lead-lag circuit
d. A twin-T filter
b
12. For oscillations to start in a circuit, the loop gain must be greater than 1 when the phase shift around the loop is
a. 90 degrees
b. 180 degrees
c. 270 degrees
d. 360 degrees
d
13. The most widely used LC oscillator is the
a. Armstrong
b. Clapp
C. Colpitts
d. Hartley
c
14. Heavy feedback in an LC oscillator
a. Prevents the circuit from starting
b. Causes saturation and cutoff
c. Produces maximum output voltage
d. Means B is small
b
15. When Q decreases in a Colpitts oscillator, the frequency of oscillation
a. Decreases
b. Remains the same
c. Increases
d. Becomes erratic
a
16. Link coupling refers to
a. Capacitive coupling
b. Transformer coupling
c. Resistive coupling
d. Power coupling
b
17. The Hartley oscillator uses
a. Negative feedback
b. Two inductors
c. A tungsten lamp
d. A tickler coil
b
18. To vary the frequency of an LC oscillator, you can vary
a. One resistor
b. Two resistors
c. Three resistors
d. One capacitor
d
19. Of the following, the one with the most stable frequency is the
a. Armstrong
b. Clapp
c. Colpitts
d. Hartley
b
20. The material with the piezoelectric effect is
a. Quartz
b. Rochelle salts
c. Tourmaline
d. All the above
d
21. Crystals have a very
a. Low Q
b. High Q
c. Small inductance
d. Large resistance
b
22. The series and parallel resonant frequencies of a crystal are
a. Very close together
b. Very far apart
c. Equal
d. Low frequencies
a
23. The kind of oscillator found in an electronic wristwatch is the
a. Armstrong
b. Clapp
c. Colpitts
d. Quartz crystal
d
24. A monostable 555 timer has the following number of stable states:
a. 0
b. 1
c. 2
d. 3
b
25. An astable 555 timer has the following number of stable states:
a. 0
b. 1
c. 2
d. 3
a
26. The pulse width out of a one-shot multivibrator increases when the
a. Supply voltage increases
b. Timing resistor decreases
c. UTP decreases
d. Timing capacitance increases
d
27. The output waveform of a 555 timer is
a. sinusoidal
b. triangular
c. rectangular
d. elliptical
c
28. The quantity that remains constant in a pulse-width modulator is
a. Pulse width
b. Period
c. Duty cycle
d. Space
b
29. The quantity that remains constant in a pulse-position modulator is
a. Pulse width
b. Period
c. Duty cycle
d. Space
d
30. When a PLL is locked on the input frequency, the VCO frequency
a. Is less than f0
b. Is greater than f0
c. Equals f0
d. Equals fin
d
31. The bandwidth of the low-pass filter in a PLL determines the
a. Capture range
b. Lock range
c. Free-running frequency
d. Phase difference
a
No comments:
Post a Comment