Deck 20: Nonlinear Op-Amp Circuit Applications Key

Question 1

Thermal noise is caused by speaker wires located in an environment with a high ambient temperature.

Answer 1

False

Question 2

A circuit that generates an output signal whose frequency depends on the charging of a capacitor is the

A) zero-crossing detector.
B) relaxation oscillator.
C) open-collector comparator.
D) active half-wave rectifier.

Answer 2

B

Question 3

A Schmitt trigger always produces a rectangular output.

Answer 3

True

Question 4

A Lissajous pattern appears on an oscilloscope when harmonically related signals are applied to the horizontal and vertical inputs.

Question 5

A double-ended limit detector detects when the input voltage is between two limits called the window.

Question 6

Monolithic op amps are inexpensive,versatile,and reliable.

Question 7

A circuit that adds a dc component to the input signal and has an output which is the same size and shape as the input,except for the dc shift is the

A) active positive clipper.
B) digital-to-analog converter.
C) active positive clamper.
D) multiplexer.

Question 8

A comparator has two input voltages and one output voltage which is either a low or a high voltage.

Question 9

What is the circuit that performs a calculus operation and produces an output voltage proportional to the instantaneous rate of change of the input voltage?

A) integrator
B) comparator
C) differentiator
D) oscillator

Question 10

If the output swing of a zero-crossing detector is too large for an application,back-to-back zener diodes can be used and the output will be bounded.

Question 11

An integrator circuit produces amplified sine waves at its output.

Question 12

An oscillator circuit can generate or create an output signal with

A) a sine wave input.
B) a linear ramp input.
C) a square wave input.
D) no external input.

Question 13

The trip point of a comparator is located in the center of the linear region.

Question 14

Oscillators are built with negative feedback.

Question 15

Hysteresis is desirable in a Schmitt trigger because it prevents noise from causing false triggering.

Question 16

A comparator that uses positive feedback is called a Schmitt trigger.

Question 17

What is the output waveform when a relaxation oscillator is cascaded with an integrator?

A) sine
B) square
C) rectangular
D) triangular

Question 18

A comparator is sometimes called a limit detector because a positive output indicates that the input voltage exceeds a specific limit.

Question 19

With an active peak detector circuit,the capacitor can be rapidly discharged in preparation for another input signal by using a

A) reset input.
B) bypass capacitor.
C) small load resistor.
D) virtual ground.

Question 20

Some optimized comparators have diode clamps built into input stages in order to protect sensitive circuits.

Question 21

What is a circuit that has two input voltages and one output voltage which is either a low or a high voltage?

A) comparator
B) integrator
C) differentiator
D) oscillator

Question 22

What is the output waveform of a zero-crossing detector when the input signal is any periodic signal that crosses zero threshold?

A) sine wave
B) rectangular
C) sawtooth
D) Lissajous

Question 23

Which class of amplifier uses output transistors operating as switches?

A) A
B) B
C) C
D) D

Question 24

Which of the following is not an advantage of monolithic op amps?

A) they are inexpensive
B) they are versatile
C) they are complex
D) they are reliable

Question 25

What is the circuit whose output voltage ideally switches from low to high or vice versa whenever the input voltage crosses zero?

A) comparator
B) integrator
C) differentiator
D) oscillator

Question 26

A comparator using positive feedback is usually called a

A) tunnel oscillator.
B) Schmitt trigger.
C) triac trigger.
D) differentiator.

Question 27

When the output swing of a zero-crossing detector is too large for some applications,back-to-back zener diodes are used to

A) filter the output.
B) clamp the output to a dc level.
C) bound the output.
D) rectify the output.

Question 28

In order to prevent an op amp differentiator from oscillating

A) a very small resistance is added to the input.
B) a very large resistance is added to the input.
C) a bypass capacitor is added to the output.

Question 29

Detecting the leading and trailing edges of a rectangular pulse or producing a rectangular output from a ramp input are applications of what circuit?

A) integrator
B) comparator
C) differentiator
D) oscillator

Question 30

A comparator whose positive output indicates that the input voltage exceeds a specific limit is referred to as

A) an integrator.
B) a comparator.
C) a differentiator.
D) a multiplexer.

Question 31

Comparators usually interface at their outputs with digital circuits such as ________.

A) TTL
B) JFET
C) SCR
D) PWM

Question 32

The input voltage of a comparator that causes the output voltage to switch states from low to high or vice versa is called the

A) gate signal.
B) trigger.
C) clamp point.
D) trip point.

Question 33

What can be done to alleviate speed limitations such as the slew-rate when using an op amp as a comparator?

A) use a faster op amp
B) increase the supply voltage
C) use capacitive coupling
D) decrease the negative feedback

Question 34

In order for a transistor output stage that is used with an IC comparator to work properly,an open collector must be connected to

A) an external resistor and supply voltage.
B) a transformer coupled load.
C) a coupling capacitor.
D) ground.

Question 35

Which of the following is not a nonlinear circuit?

A) comparator
B) voltage amp
C) waveshaper
D) active-diode circuit

Question 36

Any kind of unwanted signal that is not derived from or harmonically related to the input signal is referred to as ________.

A) hysteresis
B) oscillations
C) noise
D) attenuation

Question 37

False triggering of a Schmitt trigger caused by noise is prevented by

A) high voltage gain.
B) hysteresis.
C) a bypass capacitor.
D) negative feedback.

Question 38

When harmonically related signals are applied to the horizontal and vertical inputs of an oscilloscope,what is displayed?

A) negative and positive pulses
B) sine waves at a dc level
C) a sawtooth waveform
D) a Lissajous pattern

Question 39

Some of the more sophisticated Class D amps use a MOSFET H-bridge circuit for the switching devices an can attain efficiencies upwards from

A) 25 percent.
B) 50 percent.
C) 70 percent.
D) 85 percent.

Question 40

What device is typically used to protect the comparator against excessively large input voltages?

A) slow-blow fuse
B) thermistor
C) diode clamp
D) bypass capacitor

Question 41

Linear circuits include comparators,waveshapers,and active diode circuits.

Question 42

In order for an integrator to work properly,the closed-loop time constant should be how many times greater than the width of the input pulse?

A) 2
B) 4
C) 7
D) 10

Question 43

A comparator circuit that detects when the input voltage is between two limits is called

A) a limit comparator.
B) a dual detector.
C) a window comparator.
D) an input limiter.

Question 44

A circuit that performs a mathematical operation and produces a ramp of output voltage is known as

A) an integrator.
B) a comparator.
C) a differentiator.
D) an oscillator.

Question 45

A differentiator can be configured by using

A) an LC circuit.
B) an RC circuit.
C) a resonant tank circuit.
D) a pi filter.

Question 46

The duty cycle is equal to the

A) length of the pulse divided by the period.
B) width of the pulse divided by the period.
C) width of the pulse multiplied by the period.
D) width of the pulse added to the period.

Question 47

If an RC differentiator is to produce narrow spikes,the time constant should be

A) equal to the input pulse width.
B) 10 times larger than the input pulse width.
C) 10 times smaller than the input pulse width.
D) equal to the square root of R times

Question 48

What will reduce the effect of a diode's knee voltage and enable the diode circuit to rectify,clip,and clamp signals with amplitudes less than the knee voltage?

A) an op amp with negative feedback
B) an op amp with positive feedback
C) a JFET
D) a BJT

Question 49

What type waveform does a Schmitt trigger produce?

A) sine
B) square
C) rectangular
D) triangular

Question 50

Oscillators are built with and operate because of

A) negative feedback.
B) positive feedback.
C) virtual ground.
D) hysteresis.