Electronic Device Models In Perspective
by Dennis L. Feucht
Innovatia Laboratories
Newly-discovered physical principles often are the driving cause for the
invention of new kinds of devices such as the transistor. The semiconductor
phenomenon was known early in the twentieth century, but world wars and
the successful development of the alternative technology of thermionic valves,
or vacuum tubes, detracted from its emergence until the late 1940s.
It is one of the highlights in the history of electronics, and illustrates
how device models develop in engineering and why they are often a key to
technological advancement.
The transistor, like any new breakthrough in technology, was not well
understood in the 1950s. The very first transistors were bipolar, not field-effect,
devices. They were manufactured using a simple, highly obsolete process
that gave them their name of point-contact transistors. As the benefits
of transistors were quickly realized, great effort was put into their development,
and the bipolar junction transistor (BJT) soon replaced it. The quirky point-contact
transistor could show some of the negative-resistance effects of tunnel
diodes under the right conditions, adding to its mysteriousness and obscuring
the phenomena essential to transistor behavior. From an engineering viewpoint,
what was needed was to understand the essential principles underlying transistors.
In this regard, the development of electronics is no different than any
other area of engineering and leads to device modeling.
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