Deck 16: Oscillators

Question 1

The 555 timer contains

A)2 comparators.
B)4 comparators.
C)5 comparators.
D)3 comparators.

Answer 1

A

Question 2

When Q decreases in a Colpitts oscillator, the frequency of oscillation

A)remains the same.
B)decreases.
C)increases.
D)is unpredictable.

Answer 2

B

Question 3

The phase- shift oscillator usually has

A)two lead or lag circuits.
B)no feedback loop.
C)no RC sections.
D)three lead or lag circuits.

Answer 3

D

Question 4

The voltage that starts a feedback oscillator is caused by

A)the input signal from a generator.
B)thermal noise in resistors.
C)positive feedback.
D)ripple from the power supply.

Question 5

The closed- loop voltage gain, ACL, for a Wien- bridge oscillator is

A)exactly 1.
B)3, after the oscillations have built up.
C)less than 1.
D)slightly greater than 1.

Question 6

Which of the following cannot be used as the amplifier element within an oscillator?

A)Op- amp
B)BJT
C)FET
D)Thermistor

Question 7

A crystal's fundamental frequency depends upon

A)mechanical dimensions.
B)crystal thickness.
C)type of cut.
D)All of the above.

Question 8

Of the following oscillator circuit components, the one that exhibits the piezoelectric effect is the

A)capacitor.
B)crystal.
C)resistor.
D)inductor.

Question 9

Which type of LC oscillator uses a tickler coil in the feedback path?

A)Colpitts
B)Hartley
C)Clapp
D)Armstrong

Question 10

The Q of a crystal

A)is extremely high.
B)is about 10 or so in most cases.
C)is extremely low.
D)None of the above.

Question 11

The Hartley oscillator uses

A)a tungsten lamp.
B)two inductors.
C)only resistors and capacitors.
D)a tickler coil.

Question 12

A circuit that can change the frequency of oscillation with an application of a dc voltage is sometimes called an)

A)crystal oscillator.
B)astable multivibrator.
C)voltage- controlled oscillator.
D)Hartley oscillator.

Question 13

A very stable oscillator is needed to operate on a single frequency. A good choice might be a

A)Clapp.
B)VCO.
C)Hartley.
D)crystal.

Question 14

Refer to the figure above. If C5 were to open

A)the resonant frequency would be higher than normal.
B)the resonant frequency would be lower than normal.
C)there would be no signal present at Vout.
D)the circuit would draw no current from +Vcc.

Question 15

Which of the following is not an essential requirement of a feedback oscillator?

A)Amplifier circuit
B)Negative feedback network
C)Positive feedback network
D)Phase shift around the feedback loop of 0°

Question 16

Which of the following oscillator types does not use any inductors?

A)Clapp oscillator
B)Hartley oscillator
C)Colpitts oscillator
D)Wien- bridge

Question 17

The RC feedback network used in the Wien- bridge oscillator has a maximum output voltage when

A)R1 = R2 and XC1 = XC2.
B)R = 0 ▲.
C)XC = XL.
D)XL = R.

Question 18

The higher resonant frequencies of a crystal are called

A)decades.
B)octaves.
C)undertones.
D)overtones.

Question 19

A Wien- bridge oscillator uses

A)negative feedback.
B)positive feedback.
C)both types of feedback.
D)an LC tank circuit.

Question 20

In a Colpitts oscillator, which components)determine the feedback fraction, B?

A)The inductor in the tank circuit
B)The capacitors C1 and C2 in the tank circuit
C)The RF choke in the collector circuit
D)The resistors R1 and R2 in the base circuit

Question 21

Nonsinusoidal oscillators produce

A)sine waves only.
B)triangle waves.
C)square waves.
D)Either B or C above.

Question 22

In order for feedback oscillators to operate properly, the gain has to be

A)stabilized.
B)nonlinear.
C)1/4.
D)self- adjusting.

Question 23

A stable type of oscillator is

A)the crystal oscillator.
B)the Hartley oscillator.
C)the Clapp oscillator.
D)None of the above.

Question 24

One way to recognize a Colpitts oscillator is by the

A)tapped capacitors in the tank circuit.
B)three lag networks in the feedback path.
C)lead/lag network in the feedback path.
D)tapped inductors in the tank circuit.

Question 25

One way to recognize a Hartley oscillator is by the

A)tapped inductors in the tank circuit.
B)transformer used for feedback.
C)three lead networks in the feedback path.
D)tapped capacitors in the tank circuit.

Question 26

In order to sustain oscillations in a feedback oscillator, the gain should be so the product of AV × B equals _ .

A)increased, more than one
B)reduced, one
C)reduced, less than one
D)increased, much greater than one

Question 27

Refer to the figure above. If the value of VCC = 5 V, the output voltage would be

A)a square wave that varies between 0 V and 5 V.
B)5 V dc.
C)a square wave of 10 Vp- p.
D)a sine wave.