What is VLSI? Can you explain various levels of its development?

VLSI refers to Very Large scale integration. By very large scale integration we means embedding more and more logical devices in to as smaller area as possible. Previously by using physical hardware devices for every circuit and logic, circuits which normally take huge amount of space in terms of boards can be put in a space in orders of millimeters. Now a days, VLSI technology is involved in all aspects of our life, like in our computers, remote controls, cars etc.

Initially, the electronics circuits were used to be manufactured by using vacuum tubes and transistors. After this era comes the era of IC (Integrated circuits) where number of gates corresponding to 10 gates per chip started to be fabricated per chip. This was called Small scale Integration. After certain period of this Period of MSI came which is called Medium scale integration. In MSI at least 100 gates per chip used to be put on a chip. Then using large scale integration which involved fabricating adder, sub tractor, multiplexer and later on developing microprocessor and other peripheral devices on single chip.

As soon as the complexity of circuits getting more and more it became difficult to manually completed the project .So need of automation of process was felt.CAD tools were developed to design electronic circuits and functional and logical verification was done using CAD simulation tools .Now using CMOS technology million of gates can be put on a chip and using automation software design level can be easily converted from one level to other. Using the modern day technological advancement it has now become possible to fabricate full system on a single chip which has saved not only cost ,space and time but also it has helped humanity to achieve those missions which would have become impossible to complete in past.

There are following classifications of VLSI design:
Analog: Implementing data converter and amplifier on a chip
ASIC: It stands for application specific integration ICs. In this case ICS are design for specific purposes. DSP is the most famous and common areas to implement it on this.
SOC: It stands for system on chip and it contains digital and analog circuits on the same chip.
FPGAs is field programmable gate arrays and this are integrated circuits design for general purposes. By using FPGAs for our design it has become too easy to manipulate with your design without wasting your resources.
FPGAS are programmed using hardware description language. Two most common hardware languages include
Verilog &VHDL
These languages are used to design, verify and implementing logics at various levels of abstractions. VHDL and verilog both can be used to design except the differences in syntax of both these languages.