Deck 19: Circuit Theorems in Ac Analysis

Question 1

An op-amp comparator can be used to determine when an input voltage crosses a certain
reference voltage.

Answer 1

True

Question 2

Butterworth filters are characterized by a linear response in the pass band.

Answer 2

True

Question 3

A Wien-bridge oscillator produces an excellent quality square wave.

Answer 3

False

Question 4

If VIN equals 4 V in Figure 19-1, VOUT equals ________.

A)-13 V
B)13 V
C)-1 V
D)1 V

Question 5

Hartley and Colpitts oscillators can use op-amps.

Question 6

The terminals on a three-terminal regulator are input voltage, output voltage and ground.

Question 7

If in Figure 19-1, VOUT equals ________.

A)-13 V
B)13 V
C)-1 V
D)1 V

Question 8

An op-amp summing amplifier has no limitations on the number of inputs it can handle.

Question 9

If VIN equals 8 V in Figure 19-1, VOUT equals ________.

A)-1 V
B)1 V
C)13 V
D)-13 V

Question 10

A second-order filter rolls-off at 40 dB/decade.

Question 11

If the inputs are -7. , what is the output voltage?

A)4.9 V
B)-4.9 V
C)19.1 V
D)-19.1 V

Question 12

If the inputs are 8. , the output voltage equals ________.

A)9.6 V
B)-9.6 V
C)10.08 V
D)7.2 V

Question 13

If equals ________.

A)3.3 V
B)-3.3 V
C)-13 V
D)13 V

Question 14

If equals ________.

A)13 V
B)-3 V
C)3 V
D)-13 V

Question 15

If the inputs are 4. , the output voltage equals ________.

A)-6.5 V
B)13 V
C)-13 V
D)6.5 V

Question 16

If equals ________.

A)-0.8 V
B)0.8 V
C)13 V
D)-13 V

Question 17

Op-amp comparators are often used as zero-level detectors.

Question 18

A series-pass transistor is used in a voltage regulator.

Question 19

What change causes the circuit in Figure 19-2(b) to output the average of the three input voltages?

A) .
B)
C)Change to a different type of op-amp.
D)

Question 20

An op-amp integrator will produce a linear increasing output voltage for a constant negative
input voltage until cutoff is reached.

Question 21

If equals 22 V in Figure 19-3, at the fCO equals ________.

A)31.1 V
B)15.64 V
C)0
D)7.79 V

Question 22

If in Figure 19-3, the fCO equals ________.

A)65 Hz
B)650 Hz
C)26.5 kHz
D)2.65 kHz

Question 23

If in Figure 19-3, the fCO equals ________.

A)41.4 kHz
B)25.7 Hz
C)257 Hz
D)414 kHz

Question 24

The frequency response curve in Figure 19-5 represents the output from the ________, and the bandwidth is ________.

A)band-pass filter, 1050 Hz
B)band-pass filter, 678 Hz
C)band-reject filter, 1050 kHz
D)two-pole high-pass filter, 1050 Hz

Question 25

If the output voltage is 27.4 V at 822 Hz in Figure 19-5, what is the output voltage at 1.5 kHz?

A)27.4 V
B)13.7 V
C)6.85 V
D)19.4 V

Question 26

If in Figure 19-3, the output voltage at fCO equals ________.

A)13 VP
B)0 VP
C)49.5 VP
D)44.2 VP

Question 27

In Figure 19-3, what will change the circuit into a high-pass filter?

A)increasing the value of the resistor
B)switching the positions of the resistor and capacitor
C)decreasing the value of the capacitor
D)placing the capacitor in the feedback loop

Question 28

If in Figure 19-3, fCO equals ________.

A)145 Hz
B)4.8 Hz
C)48 Hz
D)1.45 kHz

Question 29

In Figure 19-4, if the frequency is decreased from the pass band to 1 decade below fCO, the output voltage drops to ________.

A)-40 dB
B)-6 dB
C)-3 dB
D)-20 dB

Question 30

If VOUT equals 12 V at 822 Hz in Figure 19-5, the output voltage equals ________ at 450 Hz.

A)4.24 V
B)1.06 V
C)8.49 V
D)2.12 V

Question 31

If in Figure 19-3, fCO equals ________.

A)5.19 Hz
B)16.9 Hz
C)169 Hz
D)51.9 Hz

Question 32

If Figure 19-3, fCO equals ________.

A)568 Mz
B)56.8 Hz
C)3.0 Hz
D)300 Hz

Question 33

If the two input voltages are 9. , what is the output voltage?

A)-8.5 V
B)-9.9 V
C)8.5 V
D)9.9 V

Question 34

If 22 V in the pass-band is input to the circuit in Figure 19-4, what is the output voltage at a frequency that is 1 decade higher?

A)31.1 V
B)22 V
C)7.75 V
D)15.5 V

Question 35

If the output voltage is 6 V at 1500 Hz in Figure 19-5, what is the output voltage at 822 Hz?

A)4.24 V
B)1.06 V
C)8.49 V
D)2.12 V

Question 36

The circuit in Figure 19-4 is known as the ________ and it rolls off at a rate of ________.

A)Butterworth high-pass filter, -40 dB/decade
B)Butterworth low-pass filter, -40 dB/decade
C)Butterworth low-pass filter, -20 dB/decade
D)Butterworth high-pass filter, -20 dB/decade

Question 37

If the inputs are 1. , what is the output voltage?

A)13 V
B)-6.2 V
C)6.2 V
D)-4.1 V

Question 38

If 22 V in the pass-band is input to the circuit in Figure 19-4, what is the output voltage at fCO?

A)8.92 V
B)7.75 V
C)31.1 V
D)15.6 V

Question 39

The curve in Figure 19-5 is from a ________ and its lower cutoff frequency equals ________.

A)two-pole high-pass filter, 1500 Hz
B)band-reject filter, 450 kHz
C)band-pass filter, 822 Hz
D)band-pass filter, 450 Hz

Question 40

The prime characteristic of the filter in Figure 19-4 is ________.

A)it only works in a high-pass configuration
B)the filter roll-off below the corner frequency is 40 dB/decade
C)it has the largest response of any filter type
D)nothing special

Question 41

The basic op-amp square wave oscillator is actually a:

A)Wein-bridge oscillator.
B)resistor-capacitor (R C)time constant oscillator.
C)sine wave oscillator.
D)all of these.

Question 42

If all four input resistors to a summing amplifier are , the feedback resistor is and all four input voltages are -2 V, the output voltage equals ________.

A)2 V
B)2.2 V
C)8 V
D)10 V

Question 43

A series-pass voltage regulator has ________.

A)a load
B)a shunt regulator
C)an error amplifier
D)all of these

Question 44

At the cutoff frequency of a filter circuit, the output voltage is:

A)-20 dB.
B)-40 dB.
C)-3 dB.
D)-10 dB.

Question 45

Using op-amps in a triangular wave oscillator results in a:

A)triangular wave output.
B)function generator output.
C)square wave output.
D)all of these.

Question 46

In a voltage-controlled oscillator (VCO), the output signal frequency is dependent on:

A)the value of a resistor-capacitor combination.
B)the value of a resistor.
C)the value of an applied voltage.
D)the value of a capacitor.

Question 47

In a Wein-bridge op-amp oscillator, the output is a repetitive:

A)square wave.
B)sine wave.
C)triangular wave.
D)all of these.

Question 48

In an inverting input op-amp integrator supplied with a square wave pulse or a step, the output is a:

A)opposite phase ramp.
B)same phase ramp.
C)opposite phase square wave.
D)sine wave.

Question 49

In a series voltage regulator, the four circuit blocks are:

A)error detector, reference voltage, series regulator, sampling circuit.
B)control element, reference voltage, error detector, sampling circuit.
C)reference voltage, series load, reference voltage, current limiter.
D)control element, reference voltage, error detector, current limiter.

Question 50

The input frequency of a single-pole, low-pass active filter increases from 1.5 kHz to 150 kHz. If the critical frequency is 1.5 kHz, the gain decreases by ________.

A)60 dB
B)3 dB
C)40 dB
D)20 dB

Question 51

If all four input resistors to a summing amplifier are and the feedback resistor is , then the gain equals ________.

A)4
B)2.2
C)1
D)unknown

Question 52

In an inverting input op-amp, differentiator supplied with a ramp or triangular wave, the output is a:

A)opposite phase ramp.
B)same phase square wave.
C)sine wave.
D)opposite phase square wave.

Question 53

Short-circuit or overload protection is an integral part of ________.

A)most JFETs
B)most three-terminal regulators
C)most op-amps
D)most TRIACs

Question 54

A series and a shunt regulator are differentiated by the circuit placement of a:

A)series resistor versus parallel resistor.
B)series transistor versus parallel transistor.
C)series reference voltage versus parallel reference voltage.
D)none of these.

Question 55

In a filter circuit, the terminology single pole means:

A)one fixed contact.
B)one single RC circuit.
C)one movable contact.
D)two cascaded RC circuits.

Question 56

If an inverting amplifier has a capacitor in the feedback loop, the circuit is known as the ________. When a square wave input is applied, the output is a ________ wave.

A)integrator, square
B)open loop, triangle
C)differentiator, triangle
D)integrator, triangle

Question 57

A three-terminal voltage regulator ________.

A)comes in a variety of voltage and current ratings
B)is available in both positive and negative voltage ratings
C)is very durable
D)all of the above

Question 58

In a scaling adder, the ________.

A)input resistors have values depending on the assigned weight of each input
B)input resistors are all different values
C)input resistors are all the same value
D)ratio RF/RIN must be the same for each input

Question 59

The purpose of a comparator is to ________.

A)detect the occurrence of a changing input voltage
B)produce a change in output when an input voltage equals a reference voltage
C)maintain a constant output when the dc input voltage changes
D)amplify an input voltage

Question 60

The output of an op-amp differentiator depends on the values of ________ and ________.

A)CIN, CF
B)RIN, RF
C)RIN, CF
D)CIN, RF