Notes

Question 1

What is a crystal-lattice?

Answer 1

atoms of purified semiconductor materials that arrange themselves into a unique pattern

Question 2

covalent bonding?

Answer 2

when adjacent atoms share their outer valence electrons to create a stable eight electron arrangement

Question 3

How to make a semiconductor a better conductor?

Answer 3

by adding a small amount of impurity into the crystal-lattice (doping)

Question 4

number of valence electrons in P-type?

Answer 4

three (trivalent)

Question 5

common trivalent elements?

Answer 5

boron, aluminum, gallium

Question 6

number of valence electrons for N-type?

Answer 6

5 (pentavalent)

Question 7

common elements for pentavalent?

Answer 7

arsenic, phosphorus, antimony

Question 8

How to dissipate heat losses?

Answer 8

mount semiconductors on aluminum sinks

Question 9

What are rectifiers used for?

Answer 9

to convert AC into DC

Question 10

half-wave rectification?

Answer 10

when only half of the AC input is converted to undirectional DC

Question 11

Full-wave rectification?

Answer 11

When both alternations of the AC waveform are converted to undirectional DC

Question 12

PIV rating must be greater than peak value, what is the calculation for 120v?

Answer 12

120v / 0.707 = 170v PIV

Question 13

What is ripple frequency?

Answer 13

number of output pulses of DC is known as ripple frequency

Question 14

How to achieve full-wave rectification?

Answer 14

using two different circuit configurations

Question 15

Average value of an AC sine wave?

Answer 15

zero

Question 16

levels of sin wave (top to bottom)

Answer 16

——Peak
_____ RMS 70.7%
_____ Average 63.4%

Question 17

What is a zener diode and what does it do?

Answer 17

usually made from silicon, looks like normal foods but works in reverse direction

Question 18

When is a zener diode used as a voltage regulator?

Answer 18

when in reverse bias

Question 19

typical zener wattage ratings?

Answer 19

250mw to 50w

Question 20

What can zeners not be tested with and why?

Answer 20

ohmmeter because the battery could be strong enough to break the voltage of the zener diode

Question 21

key points to observe when using zeners as voltage regulators?

Answer 21

• circuit with a constant load but variable input
• connect zener diode for reverse bias operation
• use series current-limiting resistor
• ensure dc input exceeds zener voltage rating

Question 22

Zener will only regulate if….?

Answer 22

variable input is higher than its own voltage rating