The document provides information about transistors including their basics, history, comparison to vacuum tubes, and types. It discusses how transistors can amplify and switch electronic signals, and are composed of semiconductor material with at least three terminals. The history outlines how the transistor was invented in 1947 at Bell Labs as an improvement over vacuum tubes, with its smaller size and lower power consumption enabling many electronic devices. Transistors eventually replaced vacuum tubes in most applications. Transistors are also categorized in different ways such as by material, structure, polarity, power rating, and application.

2.  Basics
 History
 Comparison with vacuum tubes
 Types

3. Basics
A transistor is a semiconductor device used to amplify and switch
electronic signals and electrical power. It is composed of
semiconductor material with at least three terminals for connection to
an external circuit. A voltage or current applied to one pair of the
transistor's terminals changes the current flowing through another pair
of terminals. Because the controlled (output) power can be higher
than the controlling (input) power, a transistor can amplify a signal.
Today, some transistors are packaged individually, but many more are
found embedded in integrated circuits.
The transistor is the fundamental building block of modern electronic
devices, and is ubiquitous in modern electronic systems. Following its
development in the early 1950s the transistor revolutionized the field
of electronics, and paved the way for smaller and cheaper
radios, calculators, and computers, among other things.

4. History
The thermionic triode, a vacuum tube invented in 1907, propelled the
electronics age forward, enabling amplified radio technology and long-
distance telephony. The triode, however, was a fragile device that
consumed a lot of power. Physicist Julius Edgar Lilienfeld filed a patent
for a field-effect transistor (FET) in Canada in 1925, which was
intended to be a solid-state replacement for the triode. Lilienfeld also
filed identical patents in the United States in 1926 and 1928.
However, Lilienfeld did not publish any research articles about his
devices nor did his patents cite any specific examples of a working
prototype. Since the production of high-quality semiconductor
materials was still decades away, Lilienfeld's solid-state amplifier ideas
would not have found practical use in the 1920s and 1930s, even if
such a device had been built. In 1934, German inventor Oskar Heil
patented a similar device

5. History
From November 17, 1947 to December 23, 1947, John Bardeen and Walter
Brattain at AT&T's Bell Labs in the United States, performed experiments and
observed that when two gold point contacts were applied to a crystal of
germanium, a signal was produced with the output power greater than the
input. Solid State Physics Group leader William Shockley saw the potential in
this, and over the next few months worked to greatly expand the knowledge
of semiconductors. The term transistor was coined by John R. Pierce as a
portmanteau of the term "transfer resistor". According to Lillian Hoddeson
and Vicki Daitch, authors of a biography of John Bardeen, Shockley had
proposed that Bell Labs' first patent for a transistor should be based on the
field-effect and that he be named as the inventor. Having unearthed
Lilienfeld’s patents that went into obscurity years earlier, lawyers at Bell Labs
advised against Shockley's proposal since the idea of a field-effect transistor
which used an electric field as a “grid” was not new. Instead, what
Bardeen, Brattain, and Shockley invented in 1947 was the first bipolar point-
contact transistor. In acknowledgement of this
accomplishment, Shockley, Bardeen, and Brattain were jointly awarded the
1956 Nobel Prize in Physics "for their researches on semiconductors and their
discovery of the transistor effect.“

6. Comparison with vacuum tubes
Advantages
The key advantages that have allowed transistors to replace their vacuum tube
predecessors in most applications are
• Small size and minimal weight, allowing the development of miniaturized
electronic devices.
• Highly automated manufacturing processes, resulting in low per-unit cost.
• Lower possible operating voltages, making transistors suitable for small, battery-
powered applications.
• No warm-up period for cathode heaters required after power application.
• Lower power dissipation and generally greater energy efficiency.
• Higher reliability and greater physical ruggedness.
• Extremely long life. Some transistorized devices have been in service for more than
50 years.
• Complementary devices available, facilitating the design of complementary-
symmetry circuits, something not possible with vacuum tubes.
• Insensitivity to mechanical shock and vibration, thus avoiding the problem
of microphonics in audio applications.

7. Comparison with vacuum tubes
• Limitations
• Silicon transistors typically do not operate at voltages higher than
about 1000 volts (SiC devices can be operated as high as 3000
volts). In contrast, vacuum tubes have been developed that can be
operated at tens of thousands of volts.
• High-power, high-frequency operation, such as that used in over-
the-air television broadcasting, is better achieved in vacuum tubes
due to improved electron mobility in a vacuum.
• Silicon transistors are much more vulnerable than vacuum tubes to
an electromagnetic pulse generated by a high-altitude nuclear
explosion.
• Sensitivity to radiation and cosmic rays (special radiation hardened
chips are used for spacecraft devices).
• Vacuum tubes create a distortion, the so-called tube sound, that
some people find to be more tolerable to the ear.

8. Types
Transistors are categorized by
• Semiconductor material (date first used): the metalloids germanium (1947)
and silicon (1954)— in amorphous, polycrystalline and monocrystallineform;
the compounds gallium arsenide (1966) and silicon carbide (1997), the alloy silicon-
germanium (1989), the allotrope of carbon graphene(research ongoing since 2004), etc.—
see Semiconductor material
• Structure: BJT, JFET, IGFET (MOSFET), IGBT, "other types"
• Electrical polarity (positive and negative) : NPN, PNP (BJTs); N-channel, P-channel (FETs)
• Maximum power rating: low, medium, high
• Maximum operating frequency: low, medium, high, radio frequency (RF), microwave (The
maximum effective frequency of a transistor is denoted by the term , an abbreviation
for transition frequency—the frequency of transition is the frequency at which the transistor
yields unity gain)
• Application: switch, general purpose, audio, high voltage, super-beta, matched pair
• Physical packaging: through-hole metal, through-hole plastic, surface mount, ball grid
array, power modules—see Packaging
• Amplification factor hfe or βF (transistor beta)