D6

Question 1

How many valence electrons do insulators have?

Answer 1

five or more

Question 2

How many valence electrons do conductors have?

Answer 2

3 or less

Question 3

How many valence electrons do semi conductors have?

Answer 3

exactly 4

Question 4

What are the two most commonly used semiconductor elements?

Answer 4

silicon and germanium

Question 5

Silicon is the most common semiconductor element because?

Answer 5

it can with stand higher temperatures

Question 6

Purified semiconductor materials arrange themselves into a

Answer 6

crystal-lattice structure

Question 7

Semi-conductor atoms tend to share their valence electrons in an

Answer 7

covalent bond

Question 8

To make a semiconductor a better conductor, a small amount of impurity is introduced this is called

Answer 8

doping.

Question 9

Creating a N-type semiconductor a ________ atom is used

Answer 9

pentavalent

Question 10

A N-type semiconductor has an excess of

Answer 10

electrons and is negatively charged

Question 11

To create a P-type semiconductor a ___________ element is used.

Answer 11

trivalent

Question 12

List three trivalent atoms

Answer 12

aluminum
boron
gallium

Question 13

List three pentavalent atoms

Answer 13

arsenic
antimony
phosphorous

Question 14

A P-type semiconductor has an unfilled

Answer 14

hole and is considered positively charged or less negative

Question 15

Semiconductors have a negative temperature coefficient of resistance. explain

Answer 15

this means that as the temperature increases the resistance decreases.

Question 16

When a joining a P-type material to a N-type material it creates a ____________ potential

Answer 16

barrier

Question 17

The barrier potential for silicon diodes is

Answer 17

.7 Volts

Question 18

The barrier potential for germanium diodes is

Answer 18

.3 Volts

Question 19

When the cathode is more positive than the anode (reverse bias) how is the barrier potential at the PN junction is strengthened.

Answer 19

free electrons in the N-type material attracted to the positive side
the holes in the P-type material are attracted toward the negative
depletes the junction region of any available charge carriers thus blocking current flow.

Question 20

When an external voltage is applied that makes the cathode more negative than the anode the barrier junction will weaken and

Answer 20

current will flow this is called forward bias

Question 21

As the current in a diode increases the resistance tends to decrease due to the negative temperature coefficient of semiconductors this

Answer 21

decrease in forward resistance combines with the increase in current so that the small voltage drop remains the same.

Question 22

What is PIV

Answer 22

Peak inverse voltage is the point at which a diode can no longer block current flow. Beyond this point the diode breaks down and current avalanches

Question 23

For a diode to conduct it must be

Answer 23

forward-biased

Question 24

To remember anode and cathode (only for conventional current flow

Answer 24

Current flows alphabetically, anode to cathode

Question 25

When a diode is connected across an inductive DC load so as to prevent arcing during switching operations, it is called

Answer 25

freewheeling diode

Question 26

Describe a Zener diode

Answer 26

designed to operate beyond its breakdown voltage rating in the reverse direction (reverse bias)

Question 27

If a silicon Zener diode is dropping .7 volts across it what is wrong?

Answer 27

It is hooked up back to front.

Question 28

Define Zener voltage

Answer 28

is the regulated voltage that is maintained across the Zener diode when it operates with reverse bias.

Question 29

What are Zener diodes good for?

Answer 29

voltage regulator

Question 30

How does a Zener diode regulate voltage?

Answer 30

When the breakdown voltage is reached the drop-off is sharp keeping the voltage constant.

Question 31

What must we do when installing a Zener diode as a voltage regulator?

Answer 31

DC input voltage must exceed the Zener voltage Hook Zener diode in reverse-bias instal series current-limiting resistor Connect load in parallel with Zener diode

Question 32

Photodiode is a special PN junction diode in which

Answer 32

light striking the junction increases the conductivity of the diode

Question 33

If two blocks of N-type semiconductor material are separated with a very thin layer of P-type semiconductor material then

Answer 33

a NPN transistor is created

Question 34

If the two outer blocks are made of P-type semiconductor, and if the separating layer is N-type semiconductor then

Answer 34

a PNP transistor is formed

Question 35

Signal transistors

Answer 35

are used in the milliwatt range

Question 36

Power transistors

Answer 36

are used in the watt range

Question 37

What does BJT stand for?

Answer 37

bipolar-junction transistor

Question 38

Transistor terms: Q

Answer 38

transistor

Question 39

Transistor terms:Ib

Answer 39

Base current

Question 40

Transistor terms:Ic

Answer 40

Collector current

Question 41

Transistor terms:Ie

Answer 41

Emitter current

Question 42

Transistor terms:Rb

Answer 42

Base circuit resistance (control)

Question 43

Transistor terms:Rc

Answer 43

Collector circuit resistance (load)

Question 44

Transistor terms:V Rb

Answer 44

Voltage drop across base circuit resistance

Question 45

Transistor terms: V Rc

Answer 45

Voltage drop across collector circuit resistance

Question 46

What is the advantages of using a transistor as a relay instead of a coil/contact relay?

Answer 46

``` the transistor has no contacts to pit no coil to burn out no moving parts to wear out it is completely solid-state ```

Question 47

the magnitude of the base current actually controls

Answer 47

the amount of collector current that can flow | usually by the beta factor or the transistor

Question 48

Transistor terms: Beta

Answer 48

expresses the magnitude of collector current controlled by a specific value of base current

Question 49

Transistor terms: Alpha = Ic/Ie

Answer 49

since the emitter current is always greater than the collector current alpha is always less then 1

Question 50

Transistor terms: Cut off

Answer 50

if the base current is reduced to a value close to zero then no collector current is allowed to flow.

Question 51

Transistor terms:Saturation

Answer 51

If increasing the base current any further cannot allow any more collector current to flow the transistor is said to be saturated.

Question 52

Which way does the arrow on a transistor diagram point?

Answer 52

from P to N

Question 53

Transistor terms: biasing

Answer 53

setting the value of Vce for a transistor