电子信息类专业英语李白萍第四单元译文【囚学园吧】

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电子信息类专业英语李白萍第四单元译文

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Unit 4 Microelectronics
Unit 4 Microelectronics
Passage A Introduction to Microelectronics
Passage B The Simple Atom, Conductors,
Insulators and Semiconductors
Passage C Diode and Transistor
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Unit 4 Microelectronics Passage A Introduction to Microelectronics
The exploring of space and the development of earth satellites has increased the importance of reducing the size and weight of electronic circuits. Also, even though electricity flows quite rapidly in computers the time delay of the signal in the interconnections between electronic components is an important consideration. If the interconnections are reduced in size, a computer can perform operations at a faster speed. Microelectronics involves the miniaturization of regular electronic circuits. A complete electronic circuit, an operational amplifier for example, which contains large numbers of individual interconnected components, such as diodes resistors, transistors, etc. may be formed on a very small single substrate. The complete miniaturized circuit is then called an integrated circuit.
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Unit 4 Microelectronics
Integrated circuits are small, light, rugged, and reliable. They
require less power and lower voltages than equivalent
macroscopic circuits; consequently they operate at lower
temperatures, and individual components may be close together
without exceeding the operating temperature limit. Relatively
little stray capacitance and short time delays are produced because
of the short interconnections between the individual components
in IC. Maintenance is simplified because if a component of the IC
fails the complete IC is usually replaced. Mass production
techniques of plane technology have reduced the cost of many IC
so that they are almost as inexpensive as a single transistor.
Eventually most conventional circuits will be replaced by IC.
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Unit 4 Microelectronics
There are two types of basic integrated circuit: monolithic
integrated circuit and the thin or thick film. Monolithic IC are
constructed in a single substrate of single crystal semiconductor,
usually silicon. Thin or thick films IC are formed on the surface of
an insulating material such as glass or a ceramic. Hybrid IC
contains more than a single substrate, the term hybrid is also
applied to combinations of monolithic and thin or thick film IC.
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Unit 4 Microelectronics Integrated circuits are also classified according to their functions.
Digital or logical IC are used as switches, they are either on or off. In

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Unit 4 Microelectronics
Figure9.4 shows how two junction transistor operates in its
basic circuit. As shown, the emitter-base junction will pass
current easily because the junction is forward biased. The
collector-base junction will not pass current (except for a small
leakage current) since the junction is reverse biased. (The term
back is often used in place of reverse bias.)
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Unit 4 Microelectronics
Figure4.4 Basic two-junction transistor bias circuit
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Unit 4 Microelectronics
It should be noted that the polarities of bias voltage for an
NPN transistor differ from those of a PNP transistor; however, the
net results are the same. For example, as shown in Figure9.4, the
emitter is negative with respect to the base (NPN) to produce a
forward bias. In Figure9.4, the emitter is positive with respect to
base (PNP) to produce the same forward bias. Similarly, the
collector has a reverse bias for both NPN and PNP, even though
the polarities are revered. Also, it should be noted that for normal
operation an NPN has its base biased positively with respect to its
emitter. Conversely, a PNP base is negative with respect to its
emitter.
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Unit 4 Microelectronics
(a) Basic two-junction transistor operation. During normal
operation of a two-junction transistor, current will flow between
emitter and base and between emitter and collector but not
between collector and base. Most of the current flows between
emitter and collector, because of the large voltage difference
existing between these elements (the sum of the emitter-base
voltage and the collector-base voltage). This produces a large
number of charge carriers (positive holes in a PN****egative
electrons in an NPN) that diffuse through this base region when
passing from emitter to collector (or vice versa). Few of these
charge carriers combine with the charge (positive in NPN,
negative PNP) in the base.
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Unit 4 Microelectronics
More charge carriers will be pulled out of the emitter and
made available for the collector if the base-emitter current is
increased. This can be accomplished by masking the base
more negative in a PNP transistor or by making the base more
positive in an NPN transistor.
If the base-emitter voltage is decreased, less charge
carriers will be pulled form the emitter and less emitter-
collector current will flow.
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Unit 4 Microelectronics
Since very little voltage (approximately 0.2 V for germanium
and 0.5 V for silicon) is required to produce a large current flow in

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