Semiconductor Fundamentals

Question 1

What determines if an element is classified as a conductor, insulator, or a semiconductors?

Answer 1

Their number of valence electrons in the atom.

Conductor: 1-3
Semiconductor: exactly 4
Insulator: 5-8

Question 2

What 2 semiconductor elements are commonly used for electronic devices like diodes and transistors?

Answer 2

Silicon: high current/voltage and high temperature

Germanium: low current/voltage (signal devices)

Question 3

What is meant by the term ‘covalent bonding’?

Answer 3

Sharing of valence electrons by adjoining atoms within a semiconductors crystal

Question 4

What is the essential difference between ‘N-type’ and P-type’ semiconductor materials?

Answer 4

N-Type: Doping semiconductor with pentavalent atoms (phosphorous, arsenic, antimony)

P-type: Doping semiconductor with trivalent atoms (aluminium, boron, gallium)

Question 5

What is ‘heat sink’

Answer 5

Aluminium chassis for mounting semiconductors to allow for efficient heat transfer (cooling operation)

Question 6

What are the two leads of a diode called?

Answer 6

Anode (+)
Cathode (-)

Question 7

What is meant by the term forward bias?

Answer 7

Connected polarity which will make diode ‘conduct’.

(Positive to anode, negative to cathode)

Question 8

What is meant by the term ‘reverse bias’?

Answer 8

Connected polarity which will make diode ‘block’.

Question 9

What kind of reading would you normally expect from an Ohmmeter when checking a diode?

Answer 9

• Low resistance when forward biased
• High resistance when reverse biased

Question 10

What is ‘free wheeling diode’?

Answer 10

Diode connected in reverse bias and in parallel with high inductive loads such as field windings of motors/generators