A BRIEF HISTORY OF ELECTRONICS
1. Vacuum TubeThe simplest vacuum tube -Diode- was invented by John Fleming in 1904. In
this device there is a plate which is biased with a positive potential and the
cathode which is a filament is heated with a filament supply so that it emits
electrons, they get attracted to the plate and current flows in the circuit. It
only flow of current in one direction.
In 1907, De forest invented the triode by inserting a third electrode between
cathode and the plate. The third electrode was called Grid. The cathode emits
electron and the plate is positively biased so the electron emitted are attracted
to the plate and current flows in the circuit, the grid electrode is negatively
biased and repels the electrons and causes reduction in the current in the
circuit which can be used to control the current .
The major problems with vacuum tube are that they are very large compared
to modern semiconductor and they consume way too much power.
2. First Transistor
Due to the bulkiness of vacuum tube the US government were looking for
alternatives. The job was given to Shockley, Bardeen and Brattain who
invented the first transistor at Bell Labs in 1947. In this transistor, a triangular
piece of plastic is covered with two gold sheets, one was the emitter and the
other one is the collector and this whole structure and this whole structure is
pressed on Germanium (a semiconductor) and this way a point contact was
made between emitter and germanium and between the collector and
germanium, the semiconductor was called the base and we had this emitter
base collector structure
3. Semiconductor Technology
In modern digital circuits (processers, memory) the Metal Oxide
Semiconductor (MOS) field-effect transistor are used, due to high integration
density and lower power consumption. The first MOS IC was in 1964 and it was
a shift register. In 1958, Jack Kilby demonstrated the first integrated circuit
fabricated on a single piece of germanium
4. Silicon wafer
Its diameter is 300 mm and its thickness is 0.8 mm. When we see the top view
of the wafer there is a pattern of rectangles, each rectangle is a chip. The chips
are separated from each other and are mounted on a package called DIP
package. The chips have little squares called the metal pads which are
connected to the devices inside the chip. From these metal pads there is a
metal wire bonded to the pins of the IC
 Diffusion- It is an important step in the processing steps of the wafer.
The wafer is heated to a very high temperature and a gas is passed over
the surface of wafer to dope it as a P or N type
5. MOS technology: Scaling
Shrinking of the feature size on the chip has enabled a huge number of
transistors to be integrated on a single chip. Gordon Moore (Intel Founder) in
1965, predicted that the number of transistors will double every two years,
this is known as Moore’s law
Due to all the developments, we can now talk about “system on a chip” which
is very complex