Electronic Components And Integrated Circuits

Electronic Components And Integrated Circuits

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Electronic Components And Integrated Circuits

When my father proudly displayed his new tablet to my grandfather and proclaimed that it can do almost everything a computer does, my grandfather would not believe it!! ‘How can you fit a whole computer into such a small thing?’ – was his actual concern. Well, this is the future of electronics. Computers are getting smaller and better, mobile phones are getting slimmer and ringing someone up is only one of the innumerable functions they can perform, televisions are getting flatter and there is demand for more! I once read somewhere that in the future we shall be having computers which can be folded and carried around in your pocket just like a sheet of paper! In today’s world, there is an increasing demand of electronic devices of extra-small size with improved function and low power requirement. This has paved the way for the growth of microminiaturized circuits which are responsible for the above miracles. Such an example is an integrated circuit or in short, IC.

An integrated circuit is a combination of various electronic components such as diodes, resistors, capacitors, transistors which are interconnected to form one or more complete circuits. ICs utilize the idea of electrically isolating the electronic devices from each other on a semiconductor wafer rather than mechanically cutting them apart.

The credit for the invention of the first integrated circuit goes to Jack Kilby of Texas Instruments in 1958 for the US Air force.

Construction wise, ICs can be of two types-Monolithic ICs and Hybrid ICs. A Monolithic IC contains all its electronic circuit components on a thin silicon wafer. A ‘Wafer’ is an extremely flat, circular, defect-free lightly doped silicon sheet of diameter 100-300 mm and thickness less than 1mm. A wafer is made up of a number of small identical units, usually square-shaped, each less than 1square cm and carrying an integrated circuit. Each such unit is called a ‘chip’. A chip can contain a large number of circuit components. On the other hand, a Hybrid IC is made up of multiple monolithic ICs and contains components mounted on a ceramic medium connected to one another with the help of wires.

                            The electronic circuit components in an IC are-

●        Diodeor a p-n junction which is a two terminal device formed when one side of a single crystal semiconductor is doped with donors and the other side doped with acceptors.

●        Transistorsmade up of a semiconductor (germanium or silicon) in which an n-type thin layer is sandwiched between two p-type layers or vice-versa. Some of the transistors in an IC can be transformed into diodes.

●        Resistorsmade up of a p-type layer within one of the n-type islands. Monolithic ICs use diffused resistors, thin film of which are incorporated within the ICs to achieve high resistance while taking up less space.

●        Capacitors which use either the junction capacitance of a reverse-biased p-n junction or a MOS structure. Small capacitances are fabricated in an IC due to restriction of space.

          The Transistor is the most sophisticated component in the fabrication of the IC.

Depending on the mode of operation, ICs are again of two types- Linear ICs and Digital ICs. Linear ICs, used in amplifiers, modulators, voltage regulators etc., have a linear input-output relationship. Digital ICs, used in logic circuits and computers, have a bistable action and work as switches with only ‘on’ and ‘off’ operations.

ICs offer a number of advantages over a discrete circuit  design-

●        ICs are inexpensive as they allow batch fabrication where hundreds of them can be fabricated at a time on a single silicon wafer.

●        Smaller in size and weight, they are useful where space and weight is critical such as in aircrafts and space vehicles.

●        Better reliabilitydue to smaller size restricting the chances of faulty defects in the wafer or the interconnections.

●        Decreased signal transfer time between the circuits due to large scale integration (LSI) resulting in considerable reduction in system size.

However, ICs do have certain limitations such as inability to obtain very small and very large resistors, inability to produce large capacitances, small power dissipation capacity, poor performance of p-n-p transistors, voltage sensitive IC components and inability to fabricate inductors and transformers in an IC. Some of these limitations can be expected to be removed in near future as technology progresses.

 Advancements in technology are enabling doubling of number of components in an IC every year. Memory chips with about 270 million transistors are available. And this trend of doubling is likely to continue in the future.





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