Deck 22: Regulated Power Supplies Key

Question 1

What is the condition called when the regulator will cut off the pass transistor and shut down the operation if the chip temperature becomes too high?

A) cutoff
B) temperature saturation
C) temperature shut off
D) thermal shutdown

Answer 1

D

Question 2

The quality of a power supply depends on its load regulation,line regulation,and output resistance.

Answer 2

True

Question 3

The transistor of a series regulator is called a pass transistor because the entire load current passes through it.

Answer 3

True

Question 4

The most widely used IC regulators are those with only three pins: one for the unregulated input voltage,one for the regulated output voltage,and one for ground.

Question 5

Thermal shutdown means an IC regulator will shut itself off when the internal temperature drops below a certain level.

Question 6

With the shunt type linear regulator,the regulating device is in series with the load.

Question 7

One approach to get more load current when using an IC voltage regulator is to use

A) a constant current source.
B) a smaller load.
C) cascaded regulators.
D) a current booster.

Question 8

An external transistor used to boost the output current of an IC voltage regulator is called

A) an outboard transistor.
B) a power amp.
C) a preamp.
D) an outside FET.

Question 9

The headroom voltage is defined as the difference between the input and output voltage.

Question 10

Since the ripple rejection of an IC voltage regulator is high

A) only LC filters are needed.
B) LC filters are not needed.
C) regulation is reduced.
D) output voltage is minimum.

Question 11

A switching regulator is the most efficient of all voltage regulators with full-load efficiency from about 75 to more than 95 percent.

Question 12

A simple voltage regulator can be built with a zener diode.

Question 13

An IC that contains a positive and a negative regulator in a single IC package is a

A) dual-tracking regulator.
B) double regulator.
C) multi-regulator.
D) plus and minus regulator.

Question 14

The two types of linear regulators are the shunt type and the series type.

Question 15

Efficiency is equal to input power divided by output power and then multiplied by 100 percent.

Question 16

By using a voltage regulator between the power supply and the load,line and load regulation can be improved significantly.

Question 17

An advantage of shunt regulators is that they have built-in short-circuit protection.

Question 18

Load regulation indicates how much the line voltage changes when the load changes.

Question 19

A power supply with a load regulation of less than 1 percent means that the load voltage varies less than 1 percent over the full range of load current.

Question 20

One advantage of a switching regulator is that it is simple to design and build.

Question 21

When analyzing a voltage regulator,what is the difference between the input and the output voltage called?

A) difference voltage
B) delta
C) inductive kick
D) headroom voltage

Question 22

What is the output pin found on some monolithic boost regulators called that provides a low impedance buffer and produces a rectangular output signal?

A) constant current pump
B) function generator
C) buffer generator
D) charge pump

Question 23

How does using an outboard transistor affect the efficiency of a series regulator?

A) reduces it considerably
B) increases it slightly
C) increases it considerably
D) has no effect

Question 24

A basic topology for switching regulators that always produces a negative output voltage when driven by a positive input voltage is the

A) buck regulator.
B) boost regulator.
C) buck-boost regulator.
D) series pass regulator.

Question 25

A simple voltage regulator can be built by using a

A) rectifier diode.
B) zener diode.
C) filter capacitor.
D) bridge circuit.

Question 26

Which of the following does not affect the quality of a power supply?

A) load regulation
B) line regulation
C) input resistance
D) output resistance

Question 27

Dc-to dc converters have efficiencies that range from

A) 10 to 25 percent.
B) 30 to 40 percent.
C) 45 to 60 percent.
D) 65 to 85 percent.

Question 28

Dc-to-dc converters are usually called

A) switching regulators.
B) conversion regulators.
C) dc regulators.
D) reversible regulators.

Question 29

The design technique or fundamental layout of a circuit is its ________.

A) headroom
B) foldback
C) topology
D) prototype

Question 30

A switching regulator can hold the output voltage constant under varying line and load conditions by

A) using a twin-T filter.
B) changing the duty cycle.
C) using a crow-bar circuit.
D) using direct coupling.

Question 31

The term that expresses how much the load voltage changes when the load current changes is the

A) load regulation
B) line regulation
C) output regulation.
D) output resistance.

Question 32

The most basic topology for switching regulators and one that always steps the voltage down is the

A) buck regulator.
B) boost regulator.
C) shunt regulator.
D) series regulator.

Question 33

A short-circuit protection circuit used with IC voltage regulators can be configured using

A) a slow-blow fuse.
B) current-sensing resistors and switching transistors.
C) capacitors and MOSFETs.
D) RLC filters.

Question 34

The transistor of a series voltage regulator is called a

A) pass transistor.
B) regulator transistor.
C) buck transistor.
D) boost transistor.

Question 35

In any power supply,the smaller the load regulation

A) the lower the output voltage.
B) the worse the power supply.
C) the better the power supply.
D) the higher the line regulation.

Question 36

Which of the following is the most efficient voltage regulator?

A) shunt
B) series
C) switching
D) buck

Question 37

A zener diode is what type regulator?

A) shunt
B) series
C) boost
D) buck

Question 38

Which of the following is a disadvantage of a switching voltage regulator?

A) simple design
B) easy to build
C) cost
D) noisy

Question 39

A well designed power supply has a

A) small line regulation.
B) large line regulation.
C) high output resistance.
D) high load regulation.

Question 40

Power supply line and load regulation can be significantly improved by using

A) germanium devices.
B) a voltage regulator between the power supply and load.
C) RC filters.
D) bridge circuits in the supply.

Question 41

What is often used to improve the operation and efficiency of a series regulator?

A) a power transistor
B) a germanium transistor
C) a Darlington connection
D) a MOSFET

Question 42

The most widely used IC regulators are those with how many pins?

A) 3
B) 6
C) 9
D) 14

Question 43

What is the term used to indicate that a chip turns itself off when the internal temperature becomes too high?

A) saturation temperature
B) chip overheat
C) thermal shutdown
D) cutoff temperature

Question 44

What is the term that means each circuit board has its own three-terminal regulator to supply the voltage used by components on that circuit board?

A) on-card regulation
B) line regulation
C) load regulation
D) single regulation

Question 45

With an IC regulator,what is the minimum headroom voltage needed for regulation called?

A) Thevenin's voltage
B) dropout voltage
C) breakdown voltage
D) boost voltage

Question 46

Current-sensing resistors used in series regulator circuits are typically

A) less than 1 Ω.
B) 75 Ω.
C) 300 Ω.
D) greater than 1 MΩ.

Question 47

Aside from two optional bypass capacitors,three-terminal IC voltage regulators require what other external components?

A) resistors
B) coupling capacitors
C) outboard transistors
D) none

Question 48

To avoid excessive power dissipation in a regulator's series pass transistor under shorted-load conditions,a designer can add

A) short-circuit protection.
B) crow-bar protection.
C) foldback current limiting.
D) low-power transistors.

Question 49

To protect against an accidental short,a series regulator usually includes

A) short-circuit protection.
B) a slow-blow fuse.
C) some form of current limiting.
D) a varistor.