Page 52 - Bebop to The Boolean Boogie An Unconventional Guide to Electronics Fundamentals, Components, and Processes

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Semiconductors: Diodes and ~r~~s~s~o~s
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(a) Circuit (b) Waveform

Figure 4-1 1. Resistor-NMOS transistor circuit

but a transistor’s control input can be driven by other transistors, allowing it to
be operated rnillilons of times a second.

Gallium Arsenide Semiconductors
Silicon is known as a four-valence semiconductor because it has four electrons
available to make bonds in its outermost electron shell. Although silicon is
the most commonly used semiconductor, there is another that requires some
mention. The element gallium (chemical symbol Ga) has three electrons
available in its outermost shell and the element arsenic (chemical symbol As)
has five. A crystalline structure of gallium arsenide (GaAs) is known as a 111-V
valence semiconductors and can be doped with impurities in a similar manner
to silicon.
In a number of respects, GaAs is preferable to silicon, not the least of which
is that GaAs tramistors can switch approximately eight times faster than their
silicon equivalents. However, GaAs is hard to work with, which results in

GaHs transistors being more expensive than their silicon cousins.

Lig ht-Emitting Diodes
Qn February 9, 1907, one of Marconi’s engineers, Mr. H.J. Round of
New Uork, NY, had a letter published in Electrical World magazine as follows:

8 In conversation, the Roman Numerals 111-V are pronounced “three-five.’’