Invention of transistor was the driving factor of growth in the VLSI Technology. Before we get to know about the VLSI Technology, let us have a basic knowledge of electronics evolution. Electronics deals with Circuits which involve various Active and Passive Components. These Circuits are used in various Electronic Devices and are called Electronic Circuits. Originally the components used in Electronic Circuits like diode were made up of vacuum tubes and were called discrete components. Later when the Solid State Device(SSD) was invented, the components were made up of semiconductors. Vacuum tubes had the disadvantage of its size, power requirement and reliability.


Integrated Circuit:
Integrated Circuit is the circuit in which all the Passive and Active components are fabricated onto a single chip. Initially the Integrated Chip could accommodate only a few components. As the days passed, the devices became more complex and required more number of circuits which made the devices look bulky. Instead of accommodating more circuits in the system, an Integration technology was developed to increase the number of components that are to be placed on a single chip. This Technology not only helped to reduce the size of the devices but also improved their speed. Depending upon the number of components (Transistors) to be integrated, they were categorized as SSI, MSI, LSI, VLSI, ULSI & GSI.
Small Scale Integration (SSI):
In this Technology, 1-100 Transistors were fabricated on a single chip. eg Gates , Flipflops.
Medium Scale Integration (MSI):
Using this Technology, 100-1000 number of Transistors could be integrated on a single chip. eg 4 bit Microprocessors.
Large Scale Integration
In this Technology, 1000-10000 Transistors could be integrated on a single chip. eg 8 bit Microprocessors, RAM, ROM
Very Large Scale Integration(VLSI):
In this Technology, 10000-1 Million Transistors could be accommodated. Eg 16-32 bit Microprocessors.
Ultra Large Scale Integration(ULSI):
In this Technology, 1 Million-10 Million Transistors could be accommodated. Eg Special Purpose Registers.
Giant Scale Integration (GSI):
In this Technology more than 10 Million Transistors could be accommodated. Eg Embedded Systems.


Advantages of VLSI:
VLSI has many advantages:
1. Reduces the Size of Circuits.
2. Reduces the effective cost of the devices.
3. Increases the Operating speed of circuits
4. Requires less power than Discrete components.
5. Higher Reliability
6. Occupies a relatively smaller area.
Uses of VLSI :
In today's world VLSI chips are widely used in various branches of Engineering like:
Voice and Data Communication networks
Digital Signal Processing
Computers
Commercial Electronics
Automobiles
Medicine and many more.